Cribado de la visión para los déficits de agudeza visual corregibles en niños en edad escolar y adolescentes
Resumen
Antecedentes
Aunque los efectos beneficiosos del cribado de la visión parecen ser intuitivos, se ha cuestionado el valor de dichos programas en las escuelas primarias y superiores. Además no existe claridad con respecto a la edad óptima para el cribado ni la frecuencia a la cual se debe realizar.
Objetivos
Evaluar la efectividad de los programas de cribado de la visión realizados en las escuelas para reducir la prevalencia de los déficits de agudeza visual corregibles por defectos de refracción en niños de edad escolar.
Métodos de búsqueda
Se hicieron búsquedas en el Registro Cochrane Central de Ensayos Controlados (Cochrane Central Register of Controlled Trials) (CENTRAL), que contiene el el registro de ensayos del Grupo Cochrane de Trastornos de los Ojos y la Visión (Cochrane Eyes and Vision Trials Register) (2017, número 4); Ovid MEDLINE; Ovid EMBASE; el ISRCTN registry; ClinicalTrials.gov y la ICTRP. La fecha de la búsqueda fue 3 de mayo 2017.
Criterios de selección
Se incluyeron los ensayos controlados aleatorios (ECA), incluidos los ensayos aleatorios grupales, que compararon el cribado de la visión con ningún cribado de la visión, o compararon intervenciones para mejorar el uso de las gafas o la eficiencia del cribado de la visión.
Obtención y análisis de los datos
Dos autores de la revisión examinaron de forma independiente los resultados de la búsqueda y extrajeron los datos. El resultado primario predeterminado fue el déficit de agudeza visual no corregido, o corregido de forma subóptima, debido a defectos de refracción seis meses después del cribado. Los resultados secundarios predeterminados incluyeron déficit de agudeza visual debido a defectos de refracción más de seis meses después del cribado, déficit de agudeza visual debido a causas diferentes de defectos de refracción, uso de gafas, calidad de vida, costos y efectos adversos. La certeza de la evidencia se calificó mediante GRADE.
Resultados principales
Se identificaron siete estudios relevantes. Cinco de estos estudios se realizaron en China uno en India y otro en Tanzania. En total, 9858 niños de diez a 18 años de edad se asignaron al azar en estos estudios, y 8240 (84%) se siguieron entre uno y ocho meses después del cribado. En general, se consideró que los estudios presentaban un riesgo de sesgo bajo. Ninguno de estos estudios comparó el cribado de la visión para los déficits de agudeza visual corregibles con ningún cribado.
Dos estudios compararon el cribado de la visión con la provisión de gafas gratis versus el cribado de la visión sin provisión de gafas gratis (prescripción solamente). Estos estudios proporcionan evidencia de certeza alta de que el cribado de la visión con provisión de gafas gratis da lugar a una proporción mayor de niños que utilizan gafas que si el cribado de la visión se acompaña de la provisión de una prescripción solamente (cociente de riesgos [CR] 1,60; intervalo de confianza [IC] del 95%: 1,34 a 1,90; 1092 participantes). Los estudios indican que si aproximadamente 250 de cada 1000 niños a los que se les realiza cribado de la visión más solo prescripción usan gafas al seguimiento (tres a seis meses), entonces 400 de cada 1000 (335 a 475) niños usarían gafas después del cribado de la visión y la provisión de gafas gratis. La evidencia de certeza baja indica un mejor desempeño educativo en los niños del grupo de gafas gratis (diferencia ajustada 0,11 en la puntuación matemática estandarizada; IC del 95%: 0,01 a 0,21; un estudio, 2289 participantes). En un estudio realizado en Tanzania en 2008, se informaron los costos, que indicaron un costo relativamente bajo del cribado y la provisión de gafas (evidencia de certeza baja). No hubo evidencia de ningún efecto importante de la provisión de gafas gratis sobre la agudeza visual no corregida (diferencia de medias ‐0,02 logMAR [IC del 95% ajustado por el agrupamiento: ‐0,04 a 0,01]) entre los grupos al seguimiento (evidencia de certeza moderada). No se informaron otros resultados predeterminados en esta revisión.
Dos estudios exploraron el efecto de una intervención educativa además del cribado de la visión sobre el uso de las gafas. Hubo evidencia de certeza moderada de un escaso efecto evidente de las intervenciones de educación investigadas en estos estudios además del cribado de la visión, en comparación con el cribado de la visión solo en el uso de gafas (CR 1,11; IC del 95%: 0,95 a 1,31; un estudio, 3177 participantes) o la compra de gafas relacionada con el resultado (odds ratio [OR] 0,84; IC del 95%: 0,55 a 1,31; un estudio, 4448 participantes). No se informaron otros resultados predeterminados en esta revisión.
Tres estudios compararon el cribado de la visión con las gafas pregraduadas versus el cribado de la visión con las gafas fabricadas a medida. Estos estudios aportan evidencia de certeza moderada de ninguna diferencia clínicamente significativa entre los dos tipos de gafas. En un estudio, la media de la agudeza logMAR en el mejor y peor ojo fue similar entre los grupos: diferencia de medias (DM) mejor ojo 0,03 logMAR; IC del 95%: 0,01 a 0,05; 414 participantes; DM peor ojo 0,06 logMAR; IC del 95%: 0,04 a 0,08; 414 participantes). Hubo evidencia de certeza alta de ninguna diferencia importante en el uso de gafas (CR 0,98; IC del 95%: 0,91 a 1,05; 1203 participantes) entre los dos grupos y evidencia de certeza moderada de ninguna diferencia importante en la calidad de vida entre los dos grupos (la media de la puntuación de calidad de vida se midió con la escala National Eye Institute Refractive Error Quality of Life 42 fue 1,42 mejor (1,04 peor a 3,90 mejor) en los niños con gafas pregraduadas (un estudio de 188 participantes). Aunque ninguno de los estudios informó sobre los costos directamente, las gafas pregraduadas son más baratas y pueden representar un ahorro considerable en los costos para los programas de cribado de la visión en ámbitos de bajos ingresos. Hubo evidencia de certeza baja de ninguna diferencia importante en los efectos adversos entre los dos grupos. Los efectos adversos se informaron en un estudio y fueron similares entre los grupos. Estos incluyeron visión borrosa, visión distorsionada, cefalea, desorientación, mareos, vista cansada y náuseas.
Conclusiones de los autores
El cribado de la visión más la provisión de gafas gratis mejora el número de niños que tienen y usan las gafas que necesitan en comparación con proporcionar una prescripción solamente. Lo anterior puede dar lugar a mejores resultados educativos. Las intervenciones de educación sanitaria, como actualmente se conciben y evalúan, no parecen mejorar el uso de las gafas en los niños. En ámbitos de bajos ingresos, las gafas pregraduadas pueden proporcionar una opción útil a las costosas gafas fabricadas a medida.
PICO
Resumen en términos sencillos
Cribado en niños de edad escolar y adolescentes para la reducción de la visión causada por la necesidad de gafas
¿Cuál es el objetivo de esta revisión?
El objetivo de esta revisión Cochrane fue determinar si el cribado de la visión en niños de edad escolar y adolescentes reduce el número de niños que necesitan gafas, ya sea porque no las tienen o porque tienen una prescripción equivocada.
Mensajes clave
El cribado de la visión y la provisión de gafas gratis mejora el número de niños que tienen y utilizan las gafas que necesitan. En ámbitos de bajos ingresos, las gafas pregraduadas pueden proporcionar una opción útil a las costosas gafas fabricadas a medida.
¿Qué se estudió en la revisión?
A nivel mundial, la necesidad no atendida de gafas correctivas es la principal causa de reducción de la visión en los niños; la miopía (imposibilidad de ver claramente los objetos a cierta distancia) se ha convertido en la afección ocular más frecuente. La reducción de la visión puede afectar el rendimiento académico y, por lo tanto, la posibilidad de empleo y el estado socioeconómico en la vida adulta. También se puede asociar con otros síntomas como las cefaleas. Por lo tanto, en las escuelas se han introducido programas de cribado de la visión diseñados para identificar a los niños que necesitan gafas. Dichos programas mejoran el acceso a la asistencia sanitaria en algunos niños que de otro modo no tendrían, pero el valor de estos programas de cribado es controversial. Por tanto, esta revisión se diseñó para obtener y evaluar cualquier evidencia con respecto a cómo funcionan dichos programas.
¿Cuáles son los principales resultados de la revisión?
Los autores de la revisión Cochrane encontraron siete estudios relevantes. Estos estudios evaluaron maneras de mejorar el acceso a las prescripciones de gafas proporcionadas como parte de un programa de cribado. Cinco estudios procedían de China, uno de India y uno de Tanzania. Estos estudios compararon: cribado de la visión con gafas gratis versus cribado de la visión solo; cribado de la visión con formación versus cribado de la visión solo; y cribado de la visión y gafas pregraduadas versus cribado de la visión y gafas fabricadas a medida.
La revisión muestra que:
• No hay estudios que comparen el cribado de la visión con ningún cribado de la visión (falta de evidencia).
• El cribado de la visión con provisión de gafas gratis da lugar a que más niños usen gafas después del cribado en comparación con dar a los niños solamente una prescripción (evidencia de certeza alta). Los niños del grupo de gafas gratis tuvieron mejor desempeño educativo (evidencia de certeza baja).
• El cribado de la visión con educación sanitaria diseñada para aumentar el uso de las gafas no pareció mejorar el número de niños que usaban gafas después del cribado en comparación con ninguna educación (evidencia de certeza moderada).
• Las gafas pregraduadas y las fabricadas a medida parecen proporcionar resultados visuales similares y un uso similar de las gafas (evidencia de certeza moderada y alta).
¿Cuál es el grado de actualización de esta revisión?
Los autores de la revisión Cochrane buscaron estudios que se habían publicado hasta el 3 mayo 2017.
Authors' conclusions
Summary of findings
| Vision screening and provision of free spectacles compared with vision screening and provision of prescription for correctable visual acuity deficits in school‐age children and adolescents | ||||||
| Patient or population: school‐age children and adolescents Settings: schools Intervention: vision screening and provision of free spectacles Comparison: vision screening and provision of prescription | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed risk1 | Corresponding risk | |||||
| prescription | free spectacles | |||||
| Uncorrected visual acuity deficit due to refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Uncorrected visual acuity deficit due to refractive error Follow‐up: more than 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Visual acuity deficit due causes other than refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Spectacle wearing Follow‐up: 6 months | Low uptake of spectacles | RR 1.60 (1.34 to 1.90) | 1092 (2 RCTs) | ⊕⊕⊕⊕ | ||
| 250 per 1000 | 400 per 1000 | |||||
| High uptake of spectacles | ||||||
| 750 per 1000 | 1000 per 1000 | |||||
| Quality of life Follow‐up: 6 months | ‐ | ‐ | ‐ | 2289 (1 RCT) | ⊕⊕⊝⊝ | In one study in China, children who received free spectacles had better educational attainment as measured by a standardised mathematics score (adjusted difference 0.11 (95% CI 0.01 to 0.21). This difference is equivalent to approximately half a term (semester) of additional learning. |
| Cost | In one study in Tanzania in 2008 the overall cost of screening and spectacle provision for each screened student was USD 0.87. The overall cost of screening and spectacle provision for each student who used spectacles was USD 46.3 (GBP 23.40) for free spectacles; USD 64.7 (GBP 32.70) for prescribed spectacles. Calculations were based on spectacle use of 47% if spectacles were provided free and 26% if spectacles were only prescribed. | ⊕⊕⊝⊝ | ||||
| Adverse effects Follow‐up: any time period | One study investigated the impact of assignment to free spectacles compared with prescription only on uncorrected visual acuity at follow‐up. There was a mean difference of ‐0.02 logMAR (95% CI adjusted for clustering ‐0.04 to 0.01) between the groups i.e. no evidence of any important impact of free spectacles on uncorrected acuity. | ⊕⊕⊕⊝ | Not reported | |||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1Spectacle wearing in the comparator groups of studies included in this review varied from 23% to 96%. We have chosen 25% and 75% as illustrative risks. | ||||||
| Vision screening and educational intervention compared with vision screening and no educational intervention for school‐age children and adolescents | ||||||
| Patient or population: school‐age children and adolescents Settings: schools Intervention: vision screening and educational intervention Comparison: vision screening and no educational intervention | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed1 risk | Corresponding risk | |||||
| Educational intervention | No educational intervention | |||||
| Uncorrected visual acuity deficit due to refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Uncorrected visual acuity deficit due to refractive error Follow‐up: more than 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Visual acuity deficit due causes other than refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Spectacle wearing Follow‐up: 6 months | Low uptake of spectacles | RR 1.11 (0.95 to 1.31) | 3177 (1 RCT) | ⊕⊕⊕⊝ | Another study of 4448 participants reported odds ratio of 0.84 (0.55 to 1.31) for related outcome spectacle purchase | |
| 250 per 1000 | 278 per 1000 | |||||
| High uptake of spectacles | ||||||
| 750 per 1000 | 833 per 1000 | |||||
| Quality of life Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Cost | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Adverse effects Follow‐up: any time period | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1Spectacle wearing in the comparator groups of studies included in this review varied from 23% to 96%. We have chosen 25% and 75% as illustrative risks. | ||||||
| Vision screening and provision of ready‐made spectacles compared with vision screening and provision of custom‐made spectacles for correctable visual acuity deficits in school‐age children and adolescents | ||||||
| Patient or population: school‐age children and adolescents Settings: schools Intervention: vision screening and ready‐made spectacles Comparison: vision screening and custom‐made spectacles | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed risk1 | Corresponding risk | |||||
| custom‐made | ready‐made | |||||
| Uncorrected visual acuity deficit due to refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | 414 (1 RCT) | ⊕⊕⊕⊝ | In one study, mean logMAR acuity in better and worse eye was similar between groups: MD better eye 0.03 logMAR, 95% CI 0.01 to 0.05; MD worse eye 0.06 logMAR, 95% CI 0.04 to 0.08 |
| Uncorrected visual acuity deficit due to refractive error Follow‐up: more than 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Visual acuity deficit due to causes other than refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Spectacle wearing Follow‐up: 6 months | Low uptake of spectacles | RR 0.98, (0.91 to 1.05) | 1203 (3 RCTs) | ⊕⊕⊕⊕ | ||
| 250 per 1000 | 245 per 1000 (228 to 263) | |||||
| High uptake of spectacles | ||||||
| 750 per 1000 | 735 per 1000 (683 to 788) | |||||
| Quality of life Measured using the NEI‐RQL‐42. Higher scores are better quality of life. Follow‐up: 6 months | The mean change in quality of life score between baseline and follow‐up was 4.65 (95% CI 2.45 to 6.86) in children with custom‐made spectacles | The mean quality of life score was 1.43 better (1.04 worse to 3.90 better) in children with ready‐made spectacles. | ‐ | 188 (1 RCT) | ⊕⊕⊕⊝ | Follow‐up was 2 months in this study |
| Cost | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Adverse effects Follow‐up: any time period | Adverse effects were reported in one study and were similar between groups. These included: blurred vision, distorted vision, headache, disorientation, dizziness, eyestrain and nausea | ⊕⊕⊝⊝ | ||||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1Spectacle wearing in the comparator groups of studies included in this review varied from 23% to 96%. We have chosen 25% and 75% as illustrative risks. | ||||||
Background
Description of the condition
Refractive error (need for spectacles) can be defined as the inability of an eye to bring parallel rays of light into focus on the retina resulting in a blurred image. There are three types of refractive error. Myopia (short‐sightedness) compromises distance vision. Hypermetropia (long‐sightedness) compromises near vision and, if severe enough, distance vision as well. Astigmatism, caused by a non‐spherical cornea, impairs both distance and near vision.
In normal visual development, changes in refractive error occur over the first few years of life. The majority of full‐term babies are hypermetropic at birth (Banks 1980) but this decreases with growth so that in adult life the preponderance of refractions are around zero or emmetropia (Sorsby 1964). Most of this change occurs in early childhood (Ehrlich 1997) in a process known as emmetropisation (Jensen 1995). The main risk factors for development of myopia appear to be intensive education and limited time outdoors (Morgan 2017). Myopia can be inherited (Yap 1994), possibly through the genetic determination of the axial length of the eye (Canoll 1982).
Myopia is a common condition. Some authors estimate that 34% of the world population will be affected by myopia in 2020 (uncertainty interval 26% to 43%) (Holden 2016). This corresponds to 2620 million people (1976 to 3366 million people). There is considerable global variation in the prevalence of myopia in children. A recent systematic review and meta‐analysis of population‐based studies suggested that 70% (95% credible interval (CrI) 61% to 77%) of East Asian children have myopia by the time they are 15 years old (Rudnicka 2016). East Asian was defined as Chinese, Japanese, Mongolian and Taiwanese. This high prevalence contrasts with relatively low prevalence in black children living in Africa (6%, 95% CrI 3% to 9%) and slightly higher prevalence in white children (17%, 95% CrI 11% to 25%). This review also provides evidence that there has been a 23% increase in myopia prevalence per decade in East Asian children (adjusted odds ratio per decade 1.23, 95% CrI 1 to 1.55). In contrast over the same period, the prevalence of myopia in white children has appeared to be stable (adjusted odds ratio per decade 0.85, 95% CrI 0.69 to 1.05). However, a study in the UK published since the review was done, has suggested that there has been an increase in myopia prevalence in white children, albeit to a smaller degree (from 7% in the 1960s to 16% between 2006 to 2008) (McCullough 2016).
Uncorrected refractive error is an important cause of visual impairment in children. Approximately 1% of children (13 million) worldwide are estimated to be visually impaired due to uncorrected refractive error (Resnikoff 2008). There is important global variation in the prevalence of visual impairment due to uncorrected refractive error ranging from 0.034% in the Western Pacific Region (A) to 5.94% in China (Resnikoff 2008). Studies show that children with refractive error often do not have spectacles or are not wearing optimal correction (Sharma 2012).
Uncorrected visual acuity deficit has been shown to have a negative impact on academic performance in some (Goldstand 2005; Maples 2003; ) but not all (Dirani 2010) studies. Qualitative studies have described how uncorrected visual deficits may lead to reduced focus, perseverance and class participation, affecting academic performance and leading to psychosocial stress (Dudovitz 2016),
Description of the intervention
Vision screening involves testing the visual acuity of children in schools or communities with the aim of identifying children with reduced vision.
Reduced vision is detected at screening using age‐appropriate visual acuity tests; commonly letter, picture, illiterate E or Landolt C optotypes. Although visual impairment and refractive error are correlated, the level at which refractive error becomes significant enough to impact on visual performance varies considerably depending on the individual and measurement‐specific variables (WHO 2002). Data from the Sydney Myopia Study suggests that uncorrected visual acuity of 6/9.5 or less has a high sensitivity (97.8%) and specificity (97.1%) for detecting refractive errors in adolescents (Leone 2010). Similar results were seen in the NICER study in Northern Ireland (UK) (O'Donoghue 2012).
Treatment for reduced visual acuity due to refractive error in school age children usually consists of optical correction of the error. Spectacles are a simple and effective means of correcting refractive error and are the most widely used treatment. Contact lenses are used as an alternative to spectacles in specific clinical circumstances (keratoconus, severe anisometropia, high refractive power) mainly in high‐income countries but increasingly also in urban centres of low‐ and middle‐income countries.
Provision of optical correction requires measurement of the type and degree of refractive error in each eye. This can be done clinically (by retinoscopy) or by an automated refractometer. The optical centres of the corrective lenses in spectacles must align with the visual axis of each eye. Spectacles without astigmatic correction and where the refractive error is the same in both eyes can be mass produced at low cost. These are known as 'ready‐made' spectacles.
Optical correction of the refractive error will result in a more or less immediate improvement in visual acuity to a normal level, if spectacles are worn. Whether or not children wear spectacles is an important determinant of a screening programme's success. The availability, affordability and acceptability of spectacles may affect whether any that are prescribed are actually worn. Barriers to spectacle use are likely to be complex and include cultural and economic factors. Over‐prescribing, whereby spectacles are prescribed for insignificant refractive error is probably one important factor leading to a low proportion of children wearing prescribed spectacles (Sharma 2012). Other factors may include concerns over appearance, teasing from peers, discomfort, negative parental attitudes, cost, and beliefs that spectacles will lead to weaker eyes.
There is debate as to whether optical correction can result in persistence of a refractive error that might otherwise have naturally resolved or reduced. Animal experiments suggest that emmetropisation may be affected by optical correction (Hung 1995). Currently available evidence from human populations does not provide support for this hypothesis (Walline 2011).
Visual acuity screening programmes vary with regard to who carries out the testing, for example teachers, nurses, optometrists, parents, other volunteers or computer programs (Sharma 2012). Vision screening programmes can be provided as part of the government healthcare system or can be run by non‐governmental organisations, such as charities or the private sector.
Regular screening activities for correctable visual acuity deficits are concentrated in high‐income countries. In Ohio USA, for example, children are screened at kindergarten and then bi‐annually throughout their school careers (Ohio 2004); in Sweden visual acuity is measured in pre‐school age children and again at seven and 10 years of age (Kvarnstrom 2001). In the UK routine vision screening is recommended for four‐ to five‐year‐old children only (PHE 2017). Although screening programmes have been introduced in lower‐income countries (Limburg 1999) the great majority of children never receive an eye examination and access to health services is often limited, especially in rural areas (Congdon 2008; Ma 2014; Wedner 2000; Wedner 2003).
How the intervention might work
Vision screening for correctable visual acuity deficit is expected to work by identifying children who require spectacles, but who currently do not have them, and enabling access to spectacles for those children. One of the roles of mass vision screening in this context is to improve equity of access to care.
It should be noted that visual acuity screening programmes for undetected, correctable visual acuity deficits will inevitably identify some children with reduced vision due to causes other than refractive error, for example cataract or amblyopia, although these will occur much less commonly than refractive error. Whilst these conditions are not the focus of this review, we will describe any data found regarding the proportions of such conditions detected by screening.
Why it is important to do this review
Given the high prevalence of visual impairment due to uncorrected refractive errors in children, and the simplicity of treatment, the detection and correction of refractive errors has been made one of the priorities of the World Health Organization (WHO) Vision 2020 initiative (Resnikoff 2001). Observed variation in provision of screening programmes worldwide highlights the uncertainty around the effects of such programmes (Hopkins 2013). A review of the evidence for the effectiveness of screening in reducing the proportion of school‐age children and adolescents with an uncorrected correctable visual acuity deficit is important to resolve this uncertainty and identify future directions for research.
Objectives
To evaluate the effectiveness of vision screening programmes carried out in schools to reduce the prevalence of correctable visual acuity deficits due to refractive error in school‐age children.
Methods
Criteria for considering studies for this review
Types of studies
We included randomised controlled trials (parallel or cluster design) of vision screening conducted after the first year at school. We did not have any language or date restrictions.
Types of participants
We considered participants identified by a school vision screening programme to have reduced visual acuity due either to an unidentified refractive error or suboptimal correction of a previously identified refractive error.
Types of interventions
Vision screening carried out by visual acuity assessment using any age‐appropriate vision test was the intervention of interest. We included studies applying any threshold for failure and administered by any testing personnel, measuring the following:
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monocular visual acuity, binocular visual acuity or both;
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distance visual acuity only;
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near and distance visual acuity.
Trials of interventions designed to improve the cost‐effectiveness of screening were also eligible for inclusion.
We planned the following comparisons:
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screening versus no screening;
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failure threshold of worse than 6/9 (Snellen) (or equivalent) versus failure threshold of 6/9 (Snellen) or better (or equivalent);
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type of testing personnel, that is nurses, teachers, and eye trained personnel;
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interventions to improve spectacle use versus no intervention to improve spectacle use;
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interventions to reduce cost.
Any studies of visual acuity screening at or before school entry are more likely to have amblyopia as their target condition and are therefore not relevant to this review.
Types of outcome measures
Primary outcomes
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Uncorrected, or suboptimally corrected, visual acuity deficit due to refractive error at six months after screening
Secondary outcomes
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Uncorrected or suboptimally corrected, visual acuity deficits more than six months after screening
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Visual acuity deficit due to causes other than refractive error, for example cataract, amblyopia
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Compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
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Quality of life: any formal, validated assessment of quality of life undertaken, for example, the National Eye Institute Refractive Error Quality of Life‐42 (NEI‐RQL‐42) (Hays 2003). We included assessment of general confidence, academic achievement, employment, social interaction etc
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Costs: this refers to any comparative information on costs or resources incurred at any time period.
Follow‐up: six months unless otherwise specified.
Adverse effects
We extracted data on the following adverse effects.
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Impact of correction of refractive error on the development of refractive error by comparing the prevalence and degree of refractive error in screened versus unscreened populations
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Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
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Prevalence of over prescribing
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Any other adverse effect as reported
Search methods for identification of studies
Electronic searches
The Cochrane Eyes and Vision Information Specialist conducted systematic searches in the following databases for randomised controlled trials and controlled clinical trials. There were no language or publication year restrictions. The date of the search was 3 May 2017.
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Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 4) (which contains the Cochrane Eyes and Vision Trials Register) in the Cochrane Library (searched 3 May 2017) (Appendix 1);
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MEDLINE Ovid (1946 to 3 May 2017) (Appendix 2);
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Embase Ovid (1980 to 3 May 2017) (Appendix 3);
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ISRCTN registry (www.isrctn.com/editAdvancedSearch; searched 3 May 2017) (Appendix 4);
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US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov; searched 3 May 2017) (Appendix 5);
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World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP)(www.who.int/ictrp; searched 3 May 2017) (Appendix 6).
Searching other resources
We did not do any handsearching for the current update (2018). For previous editions of this review we manually searched the British Orthoptic Journal from 2003 to publication date (years prior to 2003 had already been searched) and the following conference proceedings:
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European Strabismus Association (ESA);
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International Strabismus Association (ISA);
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American Association of Paediatric Ophthalmology and Strabismus (AAPOS);
-
Royal College of Ophthalmologists (RCO).
Data collection and analysis
Selection of studies
For previous editions of this review, one review author checked the search results and selected all reports of studies that made reference to refractive error, myopia and vision screening. Any reports that were clearly not relevant were excluded at first viewing. Two authors then screened the remaining titles and abstracts of the reports to establish if they met the inclusion criteria for this review.
For the current update, two authors independently screened the citations arising from the electronic searches using online review management software (Covidence).
Data extraction and management
For previous versions of this review, two authors independently extracted data from trials that met the inclusion criteria using the Cochrane Eyes and Vision data collection form.
For the current update, two authors independently extracted data and we used a data extraction template in Covidence (available on request). We re‐extracted data for all included studies and imported them into Review Manager 5 (Review Manager 2014) from Covidence. As two of the review authors were also authors of one of the included studies (Morjaria 2016), an independent assessor extracted data on this trial (Acknowledgements).
Assessment of risk of bias in included studies
We assessed risk of bias using the guidelines in Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011a).
We assessed the following domains for all studies.
-
Selection bias: we considered how the random sequence was generated and whether this allocation was concealed.
-
Performance bias: we considered whether the participants and personnel were masked and whether this masking was effective.
-
Detection bias: we considered whether the outcome assessors were masked and whether this was likely to be effective.
-
Attrition bias: we considered the completeness of the outcome data with particular reference to attrition and exclusions, and handling of any incomplete outcome data.
-
Selective reporting: we considered the bias introduced by selective reporting.
We also considered three additional sources of bias for cluster‐randomised studies as described in Chapter 16 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011b).
-
Baseline imbalance: this may be an issue in studies with small numbers of clusters.
-
Recruitment bias: this can occur when individuals are recruited to the trial after the clusters have been randomised.
-
Loss of clusters: this is analogous to incomplete outcome data for individuals.
We graded domains as low risk of bias, high risk of bias or unclear.
Measures of treatment effect
We used the risk ratio as the measure of effect for dichotomous variables. All of our outcomes were dichotomous with the exception of quality of life. For continuous outcomes, such as quality of life, we used the mean difference. We considered whether or not this outcome was skewed using Altman's method (Altman 1996).
Unit of analysis issues
The main unit of analysis issue in this review relates to cluster‐randomised trials. The studies included in this review were correctly reported with confidence intervals adjusted for the additional variance introduced by the cluster design. It was not always straightforward to pool the results of different studies, however, because they reported different effect measures. In order to pool the results of studies, we did an approximate analysis following guidelines in Chapter 16 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011b). We extracted the raw data and reduced the sample size to take into account the cluster design by dividing the sample size by the estimated design effect. We calculated an estimated design effect by comparing the variance with and without taking into account the clustering.
Dealing with missing data
We used data as reported by the included studies and did not impute data. We considered the risk of bias introduced by incomplete outcome data (Assessment of risk of bias in included studies). We contacted investigators for clarification as needed.
Assessment of heterogeneity
We assessed heterogeneity by examining the characteristics of the included studies. We also inspected the forest plots to assess variation in direction and size of the effect and poor overlap of confidence intervals. We tested for the statistical significance of heterogeneity using the Chi2 test, being aware that this test may have low power when there are few trials, or the trials are small, therefore a non‐significant result may not be evidence of no heterogeneity. We also calculated the I2 statistic (Higgins 2003), which describes the percentage of the variability in effect estimates that is due to heterogeneity rather than sampling error (chance) as described in Chapter 9 of the Cochrane Handbook for Systematic Reviews of Interventions (Deeks 2011).
Data synthesis
We pooled data using Cochrane's review management software (Review Manager 2014). We used a fixed‐effects model as only three studies or fewer were included in any analysis. We did a sensitivity analysis to compare the results of fixed‐effect and random‐effects models to test how robust our assumptions were as to the most relevant model.
Summary of findings
We prepared a 'Summary of findings' table for the following three comparisons following guidance in Chapter 11 of the Cochrane Handbook for Systematic Reviews of Interventions (Schünemann 2011).
-
Vision screening and provision of free spectacles compared with vision screening and provision of prescription
-
Vision screening and educational intervention compared with vision screening and no educational intervention
-
Vision screening and provision of ready‐made spectacles compared with vision screening and provision of custom‐made spectacles
The 'Summary of findings' table provides outcome‐specific information. We graded the certainty of the evidence for each outcome using the GRADE approach (Schünemann 2011) to assist with the interpretation of the findings. Each outcome was initially assessed as high certainty (as data drawn from randomised controlled trials) but we then downgraded it one level for serious (or two levels for very serious) concerns in the following domains: study limitations (risk of bias), indirectness of evidence, inconsistency, imprecision or publication bias.
The following outcomes are included in the 'Summary of findings' tables.
-
Uncorrected visual acuity deficit due to refractive error: follow‐up six months
-
Uncorrected visual acuity deficit due to refractive error: follow‐up more than six months
-
Visual acuity deficit due to causes other than refractive error: follow‐up six months
-
Spectacle wearing: follow‐up six months
-
Adverse effects: follow‐up any time period
-
Quality of life: follow‐up six months
-
Cost
Results
Description of studies
Results of the search
The original electronic searches identified a total of 901 reports of studies. Full‐text copies were obtained for three papers where no abstract was provided; we excluded all three papers as they were not trials (Cross 1985; Gole 2001; Yamada 2004). An additional 528 reports were identified in the first update of this review; none of these were eligible for inclusion. Updated searches conducted in May 2017 identified 2491 new records (Figure 1). After 715 duplicates were removed the Cochrane Information Specialist (CIS) screened the remaining 1776 records and removed 1547 references that were not relevant to the scope of the review. We screened the remaining 229 records and obtained 16 full‐text reports for further assessment. We included nine reports of seven studies (see Characteristics of included studies for details) and one study is currently awaiting classification (Wang 2017). We excluded six studies, see Characteristics of excluded studies for details. We did not identify any ongoing studies from our searches of the clinical trials registries.
Study flow diagram
Included studies
We included seven studies in this review (Congdon 2011; Morjaria 2016; RECS 2009; SIL 2014; SIL II 2015; WEAR 2017; Wedner 2008).
Study design and setting
There were four cluster‐randomised studies (Congdon 2011; SIL 2014; SIL II 2015; Wedner 2008) and three individually randomised studies (Morjaria 2016; RECS 2009; WEAR 2017). Five studies were conducted in China (Congdon 2011; RECS 2009; SIL 2014; SIL II 2015; WEAR 2017), one in India (Morjaria 2016) and one in Africa (Wedner 2008). All the studies were conducted in schools.
All the cluster‐randomised trials were analysed appropriately with standard errors adjusted for clustering by school.
Participants
Participants in these studies were male and female children, between the ages of 10 to 12 years (SIL II 2015), 11 to 15 years (Morjaria 2016), 12 to 15 years (RECS 2009; WEAR 2017), 12 to 17 years (Congdon 2011), 12 to 18 years (Wedner 2008) or an average age of 10.5 years (SIL 2014) (range not reported).
The following table shows the number of children randomised and followed up in the trials.
| Study | Number randomised | Number followed up | % followed up | Number of schools (cluster‐randomised controlled trials only) |
| 4448 | 3200 | 72% | 20 | |
| 460 | 362 | 79% | ||
| 495 | 414 | 84% | ||
| 3177 | 3054 | 96% | 252 | |
| 728 | 693 | 95% | 94 | |
| 426 | 409 | 96% | ||
| 125 | 108 | 86% | 37 | |
| Total | 9859 | 8240 | 84% |
The children recruited to these studies had visual impairment due to refractive error. The inclusion criteria are shown in the following table. Presenting visual acuity means visual acuity with usual spectacles.
| Study | Visual acuity | Minimum vision improvement with full correction | Difference between the spherical equivalent of the right and left eyes (anisometropia) D = dioptres | Minimum uncorrected spherical refractive error | Astigmatism D = dioptres |
| 6/12 or worse in either eye (presenting) | 2 or more lines in either eye | ||||
| Worse than 6/9 in better eye (presenting) | 2 or more lines in better eye | 1 D or less | Spherical equivalent corrects the visual acuity | ||
| 6/12 or worse in better eye (presenting) | Less than 2 D myopic Less than 1 D hyperopic | 1 D or more | Less than 2 D | ||
| 6/12 or worse in either eye (uncorrected) | Better than 6/12 with spectacles | ||||
| 6/12 or worse in either eye (uncorrected) | "refractive error meeting cutoffs shown to be associated with significantly greater improvement in visual acuity when corrected: myopia <0.75 diopters (D), hyperopia >þ2.00 D, or astigmatism | ||||
| 6/12 or worse in both eyes (presenting) | Better than 6/7.5 in both eyes | Less than 2 D | ‐1.00 D or less | Less than 2 D | |
| Worse than 6/12 in either eye (presenting) | |||||
There were additional criteria for trials of ready‐made versus custom‐made spectacles, that is, inter pupillary distance matched that of ready‐made spectacle frames available (i.e. 54 mm to 62 mm), and spectacle frames were of acceptable size and fit (Morjaria 2016).
Interventions and comparators
None of these studies addressed the comparison of primary interest to this review, that is, considered the prevalence of correctable, uncorrected visual acuity deficits in school‐age children and adolescents in screened populations compared with populations who had no screening.
The included studies considered strategies either to improve the uptake of spectacle wear in school vision screening programmes or to increase the cost‐effectiveness of school screening programmes. Some studies considered more than one strategy.
The interventions and comparators are set out in the following table.
| Type of intervention | Intervention | Comparator | Studies |
| Interventions to improve uptake | Provision of free spectacles | No free spectacles (prescription only) | |
| Free spectacles combined with a teacher incentive | No free spectacles or teacher incentive | ||
| Provision of voucher | No voucher (prescription only) | ||
| Educational intervention | No educational intervention | ||
| Interventions to improve efficiency or cost‐effectiveness | Ready‐made spectacles | Custom‐made spectacles | |
| Rural refractionist | University optometrist | ||
| Self‐refraction | University optometrist |
Outcomes
The studies all followed up at slightly different time periods. Follow‐up ranged from one month (RECS 2009), two months (WEAR 2017), three months (Wedner 2008), three to four months (Morjaria 2016), six months (Congdon 2011; SIL II 2015), and eight months (SIL 2014).
There was some variation in outcomes depending on the objective of the trials.
Most of the studies looked at some measure of spectacle wear, either purchase of spectacles (Congdon 2011), observed spectacle wear (Congdon 2011; Morjaria 2016; RECS 2009; SIL 2014;SIL II 2015; Wedner 2008), self‐reported spectacle wear (Congdon 2011; SIL 2014; SIL II 2015) or frequency of spectacle wear (Congdon 2011; RECS 2009; SIL II 2015). Reasons for non‐wear were also assessed (Congdon 2011;Morjaria 2016) and predictors of wear (Wedner 2008).
Fewer studies looked at visual acuity. Congdon 2011 assessed presenting and uncorrected vision, and also measured refraction along with the power of spectacles and spectacle‐corrected vision when spectacles were available. WEAR 2017 assessed the proportion with best‐corrected visual acuity better or equal to 6/6 and also considered the vector dioptric difference values between the prescription power and power measured by lensometry in the better‐seeing eye falling within 0.25 dioptres, 0.50 dioptres and 1.0 dioptre. Wedner 2008 reported the prevalence of uncorrected significant refractive error.
RECS 2009 looked at other outcomes including:
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previous and planned use
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perceived value
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adaptation time
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spectacle remakes
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symptoms
SIL 2014 reported educational attainment (maths test).
Only one study examined quality of life (WEAR 2017) using the NEI‐RQL‐42 questionnaire. The study also examined patient satisfaction and self‐reported rating of study spectacles.
Excluded studies
We excluded nine studies (Characteristics of excluded studies). For most of these studies this was because, on closer inspection it was obvious that these were not randomised controlled trials. One of these studies was a randomised controlled trial but it was addressing a different hypothesis relating to the progression of myopia (Li 2013).
Risk of bias in included studies
See Figure 2
Risk of bias summary: review authors' judgements about each risk of bias item for each included study
Allocation
Random sequence generation
Most of the trials described an adequate method of generating the random sequence. This was either by random number tables (Congdon 2011), computer‐generated using Excel (Morjaria 2016), R software (SIL 2014; SIL II 2015) or other computer generated random number (RECS 2009;Wedner 2008). WEAR 2017 did not clearly report random sequence generation.
Allocation concealment
We judged all seven studies as having adequate allocation concealment. Three of the studies were cluster‐randomised studies where the allocation of schools was done at the beginning of the study (Congdon 2011; RECS 2009; Wedner 2008).
Two studies had central allocation (SIL 2014; SIL II 2015). One study delivered the allocation in "Sequentially numbered, sealed, stamped opaque envelopes containing labels with unique study identification numbers and random allocation" "prepared by persons not involved in the trial." (Morjaria 2016).
Two studies did not specifically mention allocation concealment but the description of the study procedures suggested that enrolment was likely to have been masked. "Both the participant and those involved in data collection were masked to the type of spectacles ordered. Masking was maintained during follow‐up" (RECS 2009). "Subjects and study personnel administering the questionnaires and assessing VA were masked to study group assignment." (WEAR 2017).
Blinding
Performance bias
We judged all the studies to be at low risk of performance bias. Some studies made explicit statements as to masking of participants and carers (Morjaria 2016; RECS 2009; WEAR 2017; Wedner 2008) and certainly this masking was relatively straightforward in trials of ready‐made and custom spectacles (Morjaria 2016; RECS 2009). The cluster‐randomised trials avoided discussion of interventions in other schools (SIL 2014; SIL II 2015; Wedner 2008). This was not explicitly stated in Congdon 2011 but is likely and the overall negative result of the study suggests that significant bias unlikely.
Detection bias
Five out of the seven studies reported efforts to mask outcome assessment (Morjaria 2016; RECS 2009; SIL 2014; SIL II 2015; WEAR 2017). In Wedner 2008 this was not clearly described. Congdon 2011 did not mask the outcome assessments but any bias would have been expected to favour the intervention (education), which was not the case.
Incomplete outcome data
Follow‐up was high and reasonably balanced between groups in most studies (6) and we judged these to be at low risk of attrition bias. In SIL 2014; SIL II 2015 and WEAR 2017 follow‐up was over 95% and balanced between groups. In RECS 2009 and Wedner 2008 follow‐up was over 80% and again balanced between groups. In Morjaria 2016 follow‐up was nearly 80% in each group and balanced between groups and reasons for loss to follow‐up were unlikely to be associated with outcome, “All children not followed up in school (n = 98) had changed schools and moved to a different area.". In Congdon 2011 follow‐up was lower (72%) but again balanced so we judged it to be unclear whether this would have introduced bias.
Selective reporting
Selective reporting was harder to judge. Two studies reported all pre‐planned outcomes (Morjaria 2016; Wedner 2008), other studies did not report all pre‐planned outcomes but the missing outcomes were not relevant to the review (SIL 2014; SIL II 2015; WEAR 2017). Two studies did not report some of our pre‐specified review outcomes. Congdon 2011 did not report the prevalence of refractive error at six months and RECS 2009 did not report spectacle use at 6 to 12 months.
Other potential sources of bias
For the cluster‐randomised controlled trials only (Congdon 2011; SIL 2014; SIL II 2015; Wedner 2008) we considered three additional potential sources of bias.
Baseline imbalance
Baseline data were poorly reported at the cluster level but individual‐level data were available that largely suggested no major imbalances in these trials. Only SIL 2014 provided enough information to be confident that there were no baseline imbalances.
Loss of clusters
Again there was no strong evidence that this was a problem but only two studies provided enough information to judge definitively (SIL 2014; SIL II 2015).
Recruitment bias
Although this was not addressed directly the trials had made efforts to mask treatment assignment and we felt that recruitment bias was unlikely in a school setting.
Effects of interventions
See: Summary of findings for the main comparison Free spectacles versus no free spectacles (prescription only); Summary of findings 2 Educational intervention versus no educational intervention; Summary of findings 3 Ready‐made versus custom‐made spectacles
Interventions to improve uptake
Comparison: provision of free spectacles versus no free spectacles (prescription only)
See summary of findings Table for the main comparison.
Two studies compared provision of free spectacles versus no free spectacles (prescription only). Both of these studies were cluster‐randomised trials. Wedner 2008 randomised 37 schools in Tanzania involving 125 children aged 12 to 18 years (average age 14 years) and followed up for three months, at which point they measured spectacle use. SIL 2014 randomised 252 schools in China, with 2189 children aged on average 10.5 years and followed up for approximately eight months. This study also had a third study arm who received vouchers only.
Outcome: uncorrected visual acuity deficits due to refractive error (primary outcome) within six months of screening
Not reported
Outcome: uncorrected visual acuity deficits due to refractive error more than six months after screening
Not reported
Outcome: proportion of participants with visual acuity deficit due to causes other than refractive error at six months and more than six months
Not reported
Outcome: compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
Wedner 2008 defined spectacle wearing as either wearing spectacles or had them at school. Children who had received free spectacles were more likely to be wearing spectacles (or have them at school) (27/58, 47%) compared with children who had been given a prescription only (13/50 (26%) three months after screening. Wedner 2008 reports an odds ratio of 2.4 (95% confidence intervals (CI) 1.0 to 6.7) adjusted for clustering.
SIL 2014 defined spectacle wearing as "wearing glasses during an unannounced examination". Children who had received free spectacles were more likely to be wearing spectacles (469/1153, 41%) compared with children given a prescription only (266/1036, 26%) at follow‐up (approximately eight months after screening). SIL 2014 reported a risk ratio adjusted for baseline wear and clustering of 1.54 (95% CI 1.28 to 1.85).
It was a little difficult to pool these two different effect measures directly but an approximate analysis is provided in Figure 3. We have used the raw data and reduced the sample size to take into account the cluster design by dividing the sample size by the estimated design effect (calculated by comparing the variance with and without taking into account the clustering). The analysis suggests an approximate 60% increased wearing of spectacles in the free‐spectacles group (RR 1.60, 95% CI 1.34 to 1.90; 2 studies; 1092 participants). The results of the two studies were reasonably consistent. We judged this to be high‐certainty evidence.
Forest plot of comparison: 1 Free glasses compared with prescription only, outcome: 1.1 Spectacle wearing.
SIL 2014 also reported similar findings with self‐reported spectacle wear (RR 1.81, 95% CI 1.61 to 2.04). Wedner 2008 reported spectacle wear with the same definition as above but also including children who self‐reported that they had spectacles at home. There was a very high odds ratio of 14.3 (4.6 to 50).
In SIL 2014 children who had received a voucher were also more likely to be wearing spectacles (361/988, 37%) compared with children given a prescription only (266/1036, 26%) at follow‐up. SIL 2014 reported a risk ratio adjusted for baseline wear and clustering of 1.42 (95% CI 1.16 to 1.73).
Outcome: quality of life
SIL 2014 found that children who received free spectacles had better educational attainment as measured by a standardised mathematics score (adjusted difference 0.11 (95% CI 0.01 to 0.21). The authors state that this difference is equivalent to approximately half a term (semester) of additional learning.We judged this to be low‐certainty evidence, downgrading one level for imprecision and one level for indirectness as this outcome may be specific to location and unclear if it is applicable to other settings. .
Outcome: cost
Wedner 2008 calculated the overall cost of screening and spectacle provision for each screened student was USD 0.87. The overall cost of screening and spectacle provision for each student who used spectacles (definition 1) was USD 46.3 (GBP 23.40) for free spectacles; USD 64.7 (GBP 32.70) for prescribed spectacles. Calculations were based on spectacle use of 47% if spectacles were provided free and 26% if spectacles were only prescribed. We judged this to be low‐certainty evidence, downgrading two levels for indirectness as costs are very specific to location (Tanzania) and time period (nearly 10 years ago).
Outcome: adverse effects
Refractive error
SIL 2014 investigated the impact of assignment to free spectacles compared with prescription only on uncorrected visual acuity at follow‐up. There was a mean difference of ‐0.02 logMAR (95% CI adjusted for clustering ‐0.04 to 0.01) between the groups at follow‐up i.e. no evidence of any important impact of free spectacles on uncorrected acuity. We judged this to be moderate‐certainty evidence downgrading one level for indirectness average logMAR acuity may not adequately reflect proportion of children with important changes in uncorrected visual acuity.
Other pre‐specified outcomes were not reported.
-
Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
-
Over prescribing
Comparison: free spectacles combined with a teacher incentive versus no free spectacles or teacher incentive
Only one study reported the effect of supplying free spectacles alongside a teacher incentive compared with receiving a prescription only in Chinese schools (SIL II 2015). Teachers and children received an educational intervention. The teacher received a tablet computer (approximate value USD 350) if 80% or more of the children who received spectacles were wearing them.
Outcome: uncorrected visual acuity deficits due to refractive error (primary outcome) within six months of screening
Not reported
Outcome: uncorrected visual acuity deficits due to refractive error more than six months after screening
Not reported
Outcome: proportion of participants with visual acuity deficit due to causes other than refractive error at six months and more than six months
Not reported
Outcome: compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
Spectacle wear was higher at six months in children who had received free spectacles 233/341 and whose teachers had received an incentive (68.3%) compared with children who did not receive free spectacles and whose teachers did not receive an incentive (84/352 (23.9%)). The following effect estimates were reported by SIL II 2015.
-
Odds ratio adjusted for cluster design: 6.88, 95% CI 4.09 to 11.6
-
Odds ratio adjusted for cluster design and other predictor variables: 11.5, 95% CI 5.91 to 22.5.
Note that the odds ratio will give exaggerated estimates of effect. For example, the odds ratio of 6.88 will correspond to a risk ratio of 2.86.
Outcome: adverse effects
The following outcomes were not reported.
-
Refractive error
-
Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
-
Over prescribing
Outcome: quality of life
Not reported
Comparison: educational intervention versus no educational intervention
See summary of findings Table 2.
Two cluster randomised trials, both conducted in China, explored the effect of an educational intervention. In Congdon 2011 children aged between 12 to 17 years in rural China, received a lecture, video and classroom demonstration promoting spectacle purchase or no education intervention. In SIL 2014 children aged between 10 and 12 watched a 10‐minute, documentary‐style video and were given a booklet of cartoons, followed by a classroom discussion led by study staff. "These materials showed children experiencing the benefits of glasses and teachers explaining that glasses do not harm vision". Teachers and parents also viewed a presentation on the safety and benefits of spectacles. The control group received no educational intervention.
Outcome: uncorrected visual acuity deficits due to refractive error (primary outcome) within six months of screening
Not reported
Outcome: uncorrected visual acuity deficits due to refractive error more than six months after screening
Not reported
Outcome: proportion of participants with visual acuity deficit due to causes other than refractive error at six months and more than six months
Not reported
Outcome: compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
In SIL 2014 spectacle wearing was defined as "wearing glasses during an unannounced examination". A similar proportion of children in the educational intervention group were wearing spectacles (588/1648, 36%) compared with children in the group with no educational intervention (508/1529, 33%) at follow‐up (approximately eight months after screening). SIL 2014 reported a risk ratio adjusted for baseline wear and clustering of 1.11 (95% CI 0.95 to 1.31). We judged this to be moderate‐certainty evidence, downgrading one level for imprecision.
Congdon 2011 reported a related outcome measure, that is, whether or not the child obtained spectacles. A smaller proportion of the children in the educational group, reported buying spectacles (417, 25.7%) compared with the control group (537, 34.0%) at approximately six months' follow‐up. Congdon 2011 reported the following effect measures.
-
Odds ratio 0.84, 95% CI 0.55 to 1.31, adjusted for cluster design
-
Odds ratio 0.86, 95% CI 0.66 to 1.11, adjusted for cluster design and other predictors.
Outcome: quality of life
Not reported
Outcome: adverse effects
The following outcomes were not reported.
-
Refractive error
-
Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
-
Over prescribing
Interventions to improve efficiency or cost‐effectiveness
Comparison: ready‐made spectacles versus custom‐made spectacles
See summary of findings Table 3.
Ready‐made spectacles have the same spherical equivalent in both eyes and are available in a range of powers and interpupillary distances. Custom‐made spectacles are tailored to the individual prescription of the child.
Three individually randomised studies explored the use of ready‐made versus custom‐made spectacles, two studies in China (RECS 2009; WEAR 2017) and one in India (Morjaria 2016).
Outcome: uncorrected visual acuity deficits due to refractive error (primary outcome) within six months of screening
RECS 2009 reported slightly worse visual acuity in children wearing ready‐made spectacles compared with children wearing custom‐made spectacles. Mean logMAR acuity was 0.11 (standard deviation (SD) 0.09) for children wearing ready‐made spectacles and 0.08 (SD 0.07) in children wearing custom‐made spectacles (mean difference (MD) 0.03 logMAR score, 95% CI 0.01 to 0.05; 414 participants). However, this difference, of less than 5 letters, is unlikely to represent a meaningful difference between the groups. This analysis was for the eye with the lower amount of spherical refractive error, that is, the better eye. As ready‐made spectacles were dispensed on the basis of the less myopic eye the same analysis on the worse eye (eye with higher spherical refractive error) was 0.14 (SD 0.12) logMAR score in the ready‐made spectacle group compared with 0.08 (SD 0.08) in the custom‐made spectacle group (MD 0.06, 95% CI 0.04 to 0.08). We judged this to be moderate‐certainty evidence. Children with astigmatism of 0.75 dioptres or more had approximately 1 line of Snellen acuity worse with ready‐made spectacles than with custom‐made spectacles.
Outcome: uncorrected visual acuity deficits due to refractive error more than six months after screening
Not reported
Outcome: proportion of participants with visual acuity deficit due to causes other than refractive error at six months and more than six months
Not reported
Outcome: compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
All three studies found similar proportions of children in the ready‐made versus custom‐made spectacles group were wearing spectacles at follow‐up, with an overall pooled risk ratio of 0.98 (95% CI 0.91 to 1.05; 1203 participants; I2 = 0%) Figure 4. This analysis was done using a fixed‐effect model. We compared this with a random‐effects model with similar results (RR 0.98, 95% CI 0.94 to 1.03).
Forest plot of comparison: 2 Ready‐made versus custom‐made spectacles, outcome: 2.1 Spectacle wearing.
Outcome: quality of life
WEAR 2017 measured quality of life using the NEI‐RQL‐42 questionnaire. There was no evidence of any important difference in quality of life with the two types of spectacles. After wearing ready‐made spectacles for two months, the mean NEI‐RQL‐42 global score had changed from 59.6 (SD 10.6) at baseline to 64.3 (SD 11.8) in children with ready‐made spectacles. This is a change of 4.65 (95% CI 2.45 to 6.86). In the custom‐made spectacles group, mean NEI‐RQL changed to a similar degree (MD 1.43, 95% CI ‐1.04 to 3.90). We judged this to be moderate‐certainty evidence, downgrading one level for indirectness as follow‐up was two months (rather than six months specified) and reported in only one location (China).
Outcome: adverse effects
The following outcomes were not reported.
-
Refractive error
-
Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
-
Over prescribing
The following symptoms were reported in RECS 2009 at one month's follow‐up:
| Symptom n (%) | Ready‐made spectacles n = 209 | Custom‐made spectacles n = 205 |
| Blurred vision | 44 (21) | 40 (19) |
| Distorted vision | 22 (11) | 19 (9) |
| Headache | 42 (20) | 47 (23) |
| Disorientation | 18 (9) | 11 (5) |
| Dizziness | 52 (25) | 40 (19) |
| Eyestrain | 110 (53) | 91 (44) |
| Nausea | 12 (6) | 19 (9) |
Comparison: rural refractionist versus university optometrist
One study addressed this comparison. WEAR 2017 was conducted in China. Children aged 12 to 15 years were randomised to subjective cycloplegic retinoscopy by a rural refractionist or by a university optometrist and followed for two months. They were given custom‐made spectacles.
Outcome: uncorrected visual acuity deficits due to refractive error (primary outcome) within six months of screening
Children receiving spectacles prescribed after assessment by a rural refractionist were less likely to have uncorrected visual acuity deficits: 25/108 (23%) had best‐corrected visual acuity worse than 6/6 compared with 78/103 (76%) of the children receiving spectacles prescribed by a university optometrist (RR 0.31, 95% CI 0.21 to 0.44; 211 participants). All children in both groups had best‐corrected visual acuity with study spectacles better than 6/12.
Outcome: uncorrected visual acuity deficits due to refractive error more than six months after screening
Not reported
Outcome: proportion of participants with visual acuity deficit due to causes other than refractive error at six months and more than six months
Not reported
Outcome: compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
Both groups self‐reported high levels of wear: 105/108 (97%) of the rural refractionist groups compared with 99/103 (96%) of the optometrist group (RR 1.01, 95% CI 0.96 to 1.06; 211 participants).
Outcome: quality of life
There was little evidence of any important differences in quality of life as measured at two months using the NEI‐RQL‐42 (WEAR 2017). (MD 1.81, 95% CI ‐1.01 to 4.63; 198 participants).
Outcome: adverse effects
The following outcomes were not reported.
-
Refractive error
-
Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
-
Over prescribing
Comparison: self‐refraction versus university optometrist
One study addressed this comparison. WEAR 2017 was conducted in China. Children aged 12 to 15 years were randomised to non‐cycloplegic self‐refraction compared with subjective cycloplegic refraction by a university optometrist and followed for two months. They were given custom‐made spectacles. Self‐refraction was done using fluid‐filled adjustable spectacles.
Outcome: uncorrected visual acuity deficits due to refractive error (primary outcome) within six months of screening
Children receiving spectacles prescribed after self‐refraction were less likely to have uncorrected visual acuity deficits: 55/102 (54%) had best‐corrected visual acuity worse than 6/6 compared with 78/103 (76%) of the children receiving spectacles prescribed by a university optometrist (RR 0.71, 95% CI 0.58 to 0.88). All children in both groups had visual acuity better than 6/9.
Outcome: uncorrected visual acuity deficits due to refractive error more than six months after screening
Not reported
Outcome: proportion of participants with visual acuity deficit due to causes other than refractive error at six months and more than six months
Not reported
Outcome: compliance with spectacles prescribed as a result of vision screening (i.e. spectacle wearing)
Both groups self‐reported high levels of wear: 98/102 (96%) of the self‐refraction group compared with 99/103 (96%) of the university optometrist group (RR 1.00, 95% CI 0.95 to 1.06).
Outcome: quality of life
There was little evidence of any important differences in quality of life as measured by change between baseline and two months in the NEI‐RQL‐42: MD 0.82, 95% CI ‐2.00 to 3.64; 188 participants).
Outcome: adverse effects
The following outcomes were not reported.
-
Refractive error
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Anxiety (from interviews, self‐completion questionnaires, focus groups etc)
-
Over prescribing
Discussion
Summary of main results
The primary aim of vision screening of school‐age children and adolescents is to identify and address visual acuity deficits due to the development of refractive error, especially myopia. While other causes of reduced vision may also be detected these occur relatively infrequently (Wallace 2017). Vision screening for refractive error in school‐age children is not expected to impact on the prevalence of refractive error itself but aims to reduce the prevalence of uncorrected refractive error. To achieve this, vision screening programmes must not only reliably detect the target condition but also ensure that treatment, in whatever form, is available, affordable and can be realistically implemented. The remit of this review was to identify RCTs (including cluster‐randomised controlled trials) that evaluated the effectiveness of screening as an intervention.
We identified seven relevant studies. Five of these studies were conducted in China with one study in India and one in Tanzania. Children enrolled in these studies were aged between 10 and 18 years. None of these studies compared vision screening for correctable visual acuity deficits versus not screening.
Two studies compared vision screening with provision of free spectacles versus vision screening with no provision of free spectacles (summary of findings Table for the main comparison). These studies provide high‐certainty evidence that vision screening with provision of free spectacles results in a higher proportion of children wearing spectacles than if vision screening is accompanied by provision of a prescription only. The studies suggest that if approximately 250 per 1000 children who are given vision screening plus prescription only are wearing spectacles at follow‐up (three to six months) then 400 per 1000 (335 to 470) would be expected to be wearing spectacles after vision screening and provision of free spectacles. Costs were reported in one study in Tanzania in 2008 and indicated a relatively low cost of screening and spectacle provision but the extent to which these can be extrapolated to other locations is unclear. One study investigated the effect of combining a teacher incentive with free spectacles and found that this may also improve spectacle wearing. Other pre‐specified outcomes of this review were not reported.
Two studies explored the effect of an educational intervention in addition to vision screening on spectacle wear (summary of findings Table 2). There was little apparent effect of the education interventions investigated in these studies in addition to vision screening, compared to vision screening alone in terms of spectacle wearing. Other outcomes were not reported.
Three studies compared vision screening with ready‐made spectacles versus vision screening with custom‐made spectacles (summary of findings Table 3). These studies provide moderate‐certainty evidence that the two types of spectacles provide similar visual results and quality of life, and high‐certainty evidence of no important difference in spectacle wearing. There was low‐certainty evidence that the adverse effects or symptoms were similar in the two groups. Although none of the studies reported on costs directly, ready‐made spectacles are cheaper and may represent considerable cost savings for vision screening programmes in lower‐income settings.
Overall completeness and applicability of evidence
VIsion screening programmes directed to school‐age children and adolescents take place in many different contexts throughout the world. They may be affected by the background prevalence of refractive error as well as the organisation and delivery of eye healthcare services in the locality, including access to affordable spectacles. The purpose and impact of vision screening may be different at different ages, for example, screening at school entry (age four to five years) differs from screening at older ages. Evidence provided in this review may not, therefore, be universally applicable and must be interpreted in context.
There are a wide variety of approaches to school‐age vision screening throughout the world. Some commentators have observed that the existence of these variations, both between and within countries, is a reflection of the low‐certainty evidence base (Rahi 2002). It is not the aim of the current review to provide a summary of current vision screening programmes but for relevant reviews see Sharma 2012 and Hopkins 2013. The studies in the current review were from Asia, the Indian subcontinent and Africa. As such, the results of these studies may be more applicable to low‐ and middle‐income settings. The children included in these trials were aged 10 to 18 years. The results of these studies will not apply to vision screening at school entry (four to five years in many countries).
This review does not provide a direct answer to the question as to what are the benefits and harms of vision screening programmes in school‐age children and adolescents. We did not identify any randomised controlled trials addressing that question. However, the included studies that compare provision of free spectacles (SIL 2014; Wedner 2008) demonstrated reasonably large differences in spectacle wearing and these were not associated with any important adverse effects. in particular SIL 2014 provides evidence that spectacle wearing did not lead to an increased progression of myopia and this is supported by other evidence (Walline 2011).
The evidence on the provision of free spectacles is reasonably robust and will be applicable to settings where such provision is not currently available. The review also provides reasonably conclusive evidence that cheaper, ready‐made spectacles may be an acceptable alternative to expensive, custom‐made spectacles in children without astigmatism or anisometropia. The finding that educational interventions, as tested so far, do not appear to be effective in improving spectacle wear may also be applicable to other higher‐income settings. It is notable that the prevalence of spectacle wearing in the comparator group in the included studies varied from 25% to 75% and possibly higher. The reasons for variation in spectacle wear are not clearly understood but may include over‐prescribing, concerns over appearance, teasing, discomfort and beliefs around spectacle wearing (Sharma 2012).
There may be unanticipated economic effects of provision of free spectacles. A recently published trial has tested out a model for sustainable provision of free spectacles (Wang 2017). Offering an upgrade option (stylish designs and scratch‐free coatings) to free spectacles resulted in greater percentage of children purchasing spectacles and increased programme income.
Certainty of the evidence
The certainty of the evidence ranged from high to low, depending on the outcome.
We judged the studies largely to be at low risk of bias and judged the estimates of effect from each individual study as reasonably secure, downgrading only for imprecision as needed for each individual effect estimate. We were concerned with the applicability of the evidence with respect to location and downgraded for indirectness, depending on the comparison and the outcome. The extent to which the findings may be extrapolated to other settings was sometimes unclear.
Potential biases in the review process
Two of the review authors (JE/PM) were involved in one of the trials (Morjaria 2016). We tried to minimise any bias in assessment of this trial by making sure that data extraction for this study was performed by a review author not involved in the trial (CP) and another independent assessor (AS ‐ see Acknowledgements).
Agreements and disagreements with other studies or reviews
The results of this review concur with other relevant reviews (Logan 2004; Mathers 2010; Rahi 2001; Rahi 2002; Wallace 2017). There is consensus that there is insufficient evidence to support the planning and development of vision screening programmes after school entry. The US Preventive Services Task Force identified no randomised controlled trials comparing screening with no screening in children aged six months to five years (Jonas 2017). The authors concluded that they could not establish whether vision screening in preschool children was better than no screening and the evidence of benefit was indirect.
We identified one review of ready‐made spectacles (Pearce 2014). Although this review also considered studies in adult populations it came to the same conclusions as the current review, that is, that ready‐made spectacles are a potential alternative to custom‐made spectacles.
Study flow diagram
Risk of bias summary: review authors' judgements about each risk of bias item for each included study
Forest plot of comparison: 1 Free glasses compared with prescription only, outcome: 1.1 Spectacle wearing.
Forest plot of comparison: 2 Ready‐made versus custom‐made spectacles, outcome: 2.1 Spectacle wearing.
Comparison 1 Free glasses compared with prescription only, Outcome 1 Spectacle wearing.
Comparison 2 Ready‐made versus custom‐made spectacles, Outcome 1 Spectacle wearing.
| Vision screening and provision of free spectacles compared with vision screening and provision of prescription for correctable visual acuity deficits in school‐age children and adolescents | ||||||
| Patient or population: school‐age children and adolescents Settings: schools Intervention: vision screening and provision of free spectacles Comparison: vision screening and provision of prescription | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed risk1 | Corresponding risk | |||||
| prescription | free spectacles | |||||
| Uncorrected visual acuity deficit due to refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Uncorrected visual acuity deficit due to refractive error Follow‐up: more than 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Visual acuity deficit due causes other than refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Spectacle wearing Follow‐up: 6 months | Low uptake of spectacles | RR 1.60 (1.34 to 1.90) | 1092 (2 RCTs) | ⊕⊕⊕⊕ | ||
| 250 per 1000 | 400 per 1000 | |||||
| High uptake of spectacles | ||||||
| 750 per 1000 | 1000 per 1000 | |||||
| Quality of life Follow‐up: 6 months | ‐ | ‐ | ‐ | 2289 (1 RCT) | ⊕⊕⊝⊝ | In one study in China, children who received free spectacles had better educational attainment as measured by a standardised mathematics score (adjusted difference 0.11 (95% CI 0.01 to 0.21). This difference is equivalent to approximately half a term (semester) of additional learning. |
| Cost | In one study in Tanzania in 2008 the overall cost of screening and spectacle provision for each screened student was USD 0.87. The overall cost of screening and spectacle provision for each student who used spectacles was USD 46.3 (GBP 23.40) for free spectacles; USD 64.7 (GBP 32.70) for prescribed spectacles. Calculations were based on spectacle use of 47% if spectacles were provided free and 26% if spectacles were only prescribed. | ⊕⊕⊝⊝ | ||||
| Adverse effects Follow‐up: any time period | One study investigated the impact of assignment to free spectacles compared with prescription only on uncorrected visual acuity at follow‐up. There was a mean difference of ‐0.02 logMAR (95% CI adjusted for clustering ‐0.04 to 0.01) between the groups i.e. no evidence of any important impact of free spectacles on uncorrected acuity. | ⊕⊕⊕⊝ | Not reported | |||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1Spectacle wearing in the comparator groups of studies included in this review varied from 23% to 96%. We have chosen 25% and 75% as illustrative risks. | ||||||
| Vision screening and educational intervention compared with vision screening and no educational intervention for school‐age children and adolescents | ||||||
| Patient or population: school‐age children and adolescents Settings: schools Intervention: vision screening and educational intervention Comparison: vision screening and no educational intervention | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed1 risk | Corresponding risk | |||||
| Educational intervention | No educational intervention | |||||
| Uncorrected visual acuity deficit due to refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Uncorrected visual acuity deficit due to refractive error Follow‐up: more than 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Visual acuity deficit due causes other than refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Spectacle wearing Follow‐up: 6 months | Low uptake of spectacles | RR 1.11 (0.95 to 1.31) | 3177 (1 RCT) | ⊕⊕⊕⊝ | Another study of 4448 participants reported odds ratio of 0.84 (0.55 to 1.31) for related outcome spectacle purchase | |
| 250 per 1000 | 278 per 1000 | |||||
| High uptake of spectacles | ||||||
| 750 per 1000 | 833 per 1000 | |||||
| Quality of life Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Cost | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Adverse effects Follow‐up: any time period | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1Spectacle wearing in the comparator groups of studies included in this review varied from 23% to 96%. We have chosen 25% and 75% as illustrative risks. | ||||||
| Vision screening and provision of ready‐made spectacles compared with vision screening and provision of custom‐made spectacles for correctable visual acuity deficits in school‐age children and adolescents | ||||||
| Patient or population: school‐age children and adolescents Settings: schools Intervention: vision screening and ready‐made spectacles Comparison: vision screening and custom‐made spectacles | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed risk1 | Corresponding risk | |||||
| custom‐made | ready‐made | |||||
| Uncorrected visual acuity deficit due to refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | 414 (1 RCT) | ⊕⊕⊕⊝ | In one study, mean logMAR acuity in better and worse eye was similar between groups: MD better eye 0.03 logMAR, 95% CI 0.01 to 0.05; MD worse eye 0.06 logMAR, 95% CI 0.04 to 0.08 |
| Uncorrected visual acuity deficit due to refractive error Follow‐up: more than 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Visual acuity deficit due to causes other than refractive error Follow‐up: 6 months | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Spectacle wearing Follow‐up: 6 months | Low uptake of spectacles | RR 0.98, (0.91 to 1.05) | 1203 (3 RCTs) | ⊕⊕⊕⊕ | ||
| 250 per 1000 | 245 per 1000 (228 to 263) | |||||
| High uptake of spectacles | ||||||
| 750 per 1000 | 735 per 1000 (683 to 788) | |||||
| Quality of life Measured using the NEI‐RQL‐42. Higher scores are better quality of life. Follow‐up: 6 months | The mean change in quality of life score between baseline and follow‐up was 4.65 (95% CI 2.45 to 6.86) in children with custom‐made spectacles | The mean quality of life score was 1.43 better (1.04 worse to 3.90 better) in children with ready‐made spectacles. | ‐ | 188 (1 RCT) | ⊕⊕⊕⊝ | Follow‐up was 2 months in this study |
| Cost | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Adverse effects Follow‐up: any time period | Adverse effects were reported in one study and were similar between groups. These included: blurred vision, distorted vision, headache, disorientation, dizziness, eyestrain and nausea | ⊕⊕⊝⊝ | ||||
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| 1Spectacle wearing in the comparator groups of studies included in this review varied from 23% to 96%. We have chosen 25% and 75% as illustrative risks. | ||||||
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Spectacle wearing Show forest plot | 2 | 1092 | Risk Ratio (M‐H, Fixed, 95% CI) | 1.60 [1.34, 1.90] |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Spectacle wearing Show forest plot | 3 | 1203 | Risk Ratio (M‐H, Fixed, 95% CI) | 0.98 [0.91, 1.05] |
