Corrección con gafas versus no corrección con gafas para la prevención del estrabismo en niños con hiperopía
Resumen
Antecedentes
La hipermetropía en la infancia requiere un esfuerzo de adaptación para enfocar las imágenes. El esfuerzo acomodativo prolongado se ha asociado con un mayor riesgo de estrabismo (desalineación ocular). El estrabismo puede dar lugar a astenopía y diplopía intermitente, lo cual da lugar a que las tareas en la que se utiliza la visión cercana sean difíciles de completar. Se cree que la prescripción de gafas para corregir el defecto de refracción de la hiperopía previene el desarrollo de estrabismo.
Objetivos
Evaluar la efectividad de las gafas prescritas en comparación con ninguna intervención para la prevención del estrabismo en lactantes y niños con hiperopía.
Métodos de búsqueda
Se hicieron búsquedas en CENTRAL (2018, número 12; que contiene el Registro Cochrane de Ensayos de Ojos y Visión [Cochrane Eyes and Vision Trials Register]); Ovid MEDLINE; Embase.com; otras tres bases de datos y dos registros de ensayos. En las búsquedas electrónicas de ensayos, no se aplicaron restricciones de fecha ni de idioma. Se buscó por última vez en las bases de datos electrónicas el 4 de diciembre 2018.
Criterios de selección
Se incluyeron ensayos controlados aleatorizados y cuasialeatorizados que investigaron la asignación a la intervención con gafas o ningún tratamiento para los niños con hiperopía. Se requirió que la hipermetropía fuera al menos mayor que +2,00 dioptrías (D).
Obtención y análisis de los datos
Se utilizaron los procedimientos metodológicos Cochrane estándar. El resultado principal fue la proporción de niños con estrabismo manifiesto, según la definición de los investigadores del estudio. Otros resultados fueron la ambliopía, la estereoagudeza y el efecto del uso de gafas en el estrabismo y la agudeza visual. También se recogió información sobre el cambio en el error de refracción como medida de la interferencia de la emetropización.
Resultados principales
Se identificaron cuatro ensayos controlados aleatorizados (985 niños incluidos con edades de entre seis y 36 meses) en esta revisión. Tres ensayos se realizaron en el Reino Unido con períodos de seguimiento que oscilaron de uno a tres años y medio y uno en los EE.UU. con tres años de seguimiento.
Los investigadores informaron sobre la incidencia y el estado final del estrabismo. La evidencia de la incidencia de estrabismo, medido en 804 niños de más de tres a cuatro años en cuatro ensayos, fue incierta aunque sugería un beneficio con el uso de gafas (riesgo relativo [RR] 0,65; intervalo de confianza [IC] del 95%: 0,41 a 1,02). Existe muy poca confianza en estos resultados debido al riesgo alto de sesgo, la inconsistencia y la imprecisión. Cuando se evaluó la proporción de niños con estrabismo al final de los tres años de seguimiento, se encontró un nivel de evidencia similar de un efecto de las gafas sobre el estrabismo que el que se informó en un estudio (RR 1,00; IC del 95%: 0,31 a 3,25; 106 niños). Existe muy poca confianza en estos resultados debido al tamaño reducido de la muestra y al riesgo de sesgo.
Un ensayo informó sobre el riesgo de desarrollar ambliopía y estereoagudeza inadecuada después de tres años en 106 niños. No hubo evidencia clara de una disminución del riesgo de desarrollar ambliopía (RR 0,78; IC del 95%: 0,31 a 1,93), y hubo evidencia limitada de un beneficio de las gafas para la prevención de la estereoagudeza inadecuada (RR 0,38; IC del 95%: 0,16 a 0,88). Existe muy poca confianza en estos hallazgos debido a la imprecisión y el riesgo de sesgo.
El riesgo de no desarrollar emetropización no está claro. Un ensayo informó sobre la proporción de niños que no lograron la emetropización a los tres años de seguimiento (RR 0,75; IC del 95%: 0,18 a 3,19). Un ensayo sugirió que las gafas impiden la emetropización, y otro ensayo no informó de ninguna diferencia. Estos dos ensayos no pudieron combinarse debido a que los métodos de evaluación de la emetropización eran diferentes. Debido al riesgo alto de sesgo y la inconsistencia, la certeza de la evidencia en cuanto al riesgo de impedir o beneficiar la emetropización es muy baja.
Sobre la base de un metanálisis de cuatro ensayos (770 niños), el riesgo de tener una agudeza visual peor que 20/30 medida hasta los tres años de edad o al final de tres años de seguimiento fue incierto para los niños con corrección con gafas en comparación con los niños sin corrección (RR 0,87; IC del 95%: 0,64 a 1,18; confianza muy baja debido al riesgo de sesgo y la imprecisión).
Conclusiones de los autores
Aún no está claro el efecto de la corrección con gafas para la prevención del estrabismo. Además, tampoco está claro el uso de gafas sobre el riesgo de una agudeza visual inferior a 20/30; la ambliopía y la emetropización inadecuada. Podría haber un beneficio sobre la prevención de una estereoagudeza inadecuada. Sin embargo, estos efectos pueden haber sido hallazgos fortuitos o pueden deberse al sesgo.
PICO
Resumen en términos sencillos
Gafas para prevenir la mala alineación de los ojos (estrabismo) en niños con visión lejana
¿Cuál era el objetivo de esta revisión?
Saber si el uso de gafas por parte de los niños hipermétropes evitará que se produzca estrabismo (ojos cruzados) y sus efectos asociados.
Mensajes clave
La evidencia actual no apoya la conclusión de que los anteojos previenen el estrabismo en los niños hipermétropes, ni que el uso de gafas previene la ambliopía (ojo perezoso). Esta evidencia fue limitada debido a que algunas partes de los estudios no se realizaron de forma adecuada y al número reducido de participantes en los mismos.
¿Qué se estudió en la revisión?
Los niños suelen presentar hipermetropía al nacer, lo que significa que solo tienen una visión clara a distancia. A medida que los niños crecen, sus ojos también crecen hasta donde pueden ver de forma clara tanto de cerca como de lejos. Alrededor del 9% de los niños siguen presentando un nivel alto de hipermetropía. La hipermetropía significa que para enfocar las cosas de cerca el niño debe realizar mucho esfuerzo. Este esfuerzo puede causar síntomas, como cefaleas, visión doble, y cansancio ocular, y también causa dificultades para realizar tareas que necesitan la visión cercana, como leer. Los niños que siguen siendo hipermétropes tienen más probabilidades que los niños con visión normal de desarrollar ojos cruzados (estrabismo), lo que puede ocurrir en el 3,5% al 5,7% de los niños, o en el 10% al 20% de los niños con altos niveles de hipermetropía. El estrabismo dificulta que los ojos trabajen en colaboración para enfocarse. Se cree que alrededor del 50% de los niños con estrabismo desarrollan ambliopía, lo que significa que el niño no puede tener una visión clara incluso cuando usa gafas. La percepción de la profundidad, o la forma en que dos cosas se relacionan entre sí en el espacio, a menudo también se ve afectada. Los médicos suelen recetar gafas para prevenir el desarrollo de estrabismo y los demás problemas asociados en los niños hipermétropes, pero no está claro si las gafas en sí pueden impedir que los ojos crezcan con normalidad.
¿Cuáles son los principales resultados de la revisión?
Se identificaron los resultados de cuatro ensayos controlados aleatorizados (estudios clínicos en los que las personas son asignadas al azar a uno de dos o más grupos de tratamiento) para determinar si los anteojos tuvieron éxito en la prevención del estrabismo en los niños hipermétropes en comparación con la ausencia de anteojos. Los ensayos incluyeron a niños de seis meses a menos de 36 meses y midieron los resultados entre los tres y cuatro años de edad. Los cuatro ensayos incluyeron a 985 niños. Se encontró evidencia poco clara de una diferencia entre los dos grupos en cuanto a la frecuencia con que se producía el estrabismo durante el período de seguimiento. También se encontró evidencia poco clara sobre si la prescripción de gafas afectaba la percepción de la profundidad o impedía que los ojos se desarrollaran de forma natural para tener una visión clara. Existe poca confianza en estos hallazgos debido a que algunas partes de los estudios no se realizaron de forma adecuada y al número pequeño de niños en los estudios.
¿Cuál es el grado de actualización de esta revisión?
Diciembre 2018.
Authors' conclusions
Summary of findings
| Spectacle correction compared with no spectacles for infants or children with hyperopia | ||||||
| Patient or population: infants or children with hyperopia Settings: pediatric eye clinics Intervention: spectacle correction Comparison: no spectacles | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| No spectacles | Spectacles | |||||
| Incidence of strabismus up to 3–4 years of age | 234 per 1000 | 152 per 1000 | RR 0.65 (0.41 to 1.02) | 804 (4 studies) | ⊕⊝⊝⊝ Very lowa,b,c | — |
| Proportion of children with strabismus at 3 years' follow‐up | 94 per 1000 | 94 per 1000 | RR 1.00 (0.31 to 3.25) | 106 children | ⊕⊝⊝⊝ Very lowa,c | — |
| Proportion of children with amblyopia at 3 years | 170 per 1000 | 133 per 1000 (53 to 328) | RR 0.78 (0.31 to 1.93) | 106 children | ⊕⊝⊝⊝ Very lowa,c | — |
| Proportion of children with inadequate stereoacuity at 3 years | 302 per 1000 | 114 per 1000 | RR 0.38 (0.16 to 0.88) | 106 children | ⊕⊝⊝⊝ Very lowa,c | — |
| Proportion of children without refractive error in the emmetropization range at 3 years | 75 per 1000 | 100 per 1000 (14 to 239) | RR 0.75 (0.18 to 3.19) | 106 children | ⊕⊝⊝⊝ Very lowa,c | Emmetropization was also reported as:
|
| Visual acuity worse than 20/30 at 3–4 years of age | 183 per 1000 | 159 per 1000 | RR 0.87 (0.64 to 1.18) | 770 (4 studies) | ⊕⊝⊝⊝ | — |
| *The basis for the assumed risk (e.g. the mean 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). CI: confidence interval; D: diopter; n: number of participants; RR: risk ratio; SD: standard deviation. | ||||||
| GRADE Working Group grades of evidence | ||||||
| aDowngraded one level for risk of bias because studies were at high or unclear risk of bias for allocation concealment and high risk of bias for masking. | ||||||
Background
Description of the condition
Hyperopia, also known as far‐sightedness or long‐sightedness, is a condition that arises when the image produced by light rays is focused behind the retina. In hyperopia, vision is blurred and requires accommodative effort to produce a clear image. Should the level of hyperopia be too great, accommodation will not be sufficient to overcome the amount of hyperopia without increasing the risk of strabismus and the eventual development of amblyopia (lazy eye), as well as resulting in symptoms such as blurry vision. Prolonged accommodative effort can result in strabismus, a condition commonly known as crossed eyes (also known as squint) (Babinsky 2013). Among full‐term infants, one expects to see low to moderate levels of hyperopia that generally resolve as the child's vision emmetropizes (normalizes) (Goldschmidt 1969), which occurs, in large part, by nine to 12 months of age (Mutti 2004). A proportion of children have such high levels of hyperopia that the vision may not reach normal levels. Ingram 2000 found up to 9% of children retained at least +4.0 diopters (D) of hyperopia at six months old, and estimated that approximately 20% of these children may develop some type of visual problem. Atkinson 1996 estimated that infants with at least +3.50 D of hyperopia were 13 times more likely to develop strabismus by four years of age than infants with less hyperopia, and they were six times more likely to have decreased vision than those infants with less hyperopia or emmetropia or 'normal' vision. While most hyperopic eyes will eventually emmetropize, strabismus and subsequent amblyopia present a real danger to children whose eyes do not normalize. Amblyopia is a loss of vision for which eyeglasses and contact lenses may not restore full vision, though early treatment of children with refractive correction, patching, or drug therapy has been successful (Li 2009; Taylor 2011; Taylor 2012). Amblyopia that has not been identified or treated eventually may lead to vision loss (Holmes 2006). Children with amblyopia also are believed to be at a higher risk of losing vision in the unaffected eye when compared with the general population (Tomilla 1981; van Leeuwen 2007). Because of the more serious consequences of amblyopia, seeking ways to limit the development of strabismus can decrease one of the contributing factors for amblyopia.
After refractive error, strabismus is the next leading cause of eye problems among infants and young children, and has been reported to occur in 3.7% to 5.3% of children (Cotter 1997). If the strabismic child is not given appropriate treatment, strabismus can lead to the development of amblyopia or prevent the development of binocularity, which is the ability of the eyes to work together to produce a single image (Cotter 1997). Strabismus can manifest in different ways. When the eye turns inward to the nose, this condition is called an esotropia, while the eye turning outward is known as exotropia. Sometimes the tropia can be vertical (up or down). Together these are types of manifest strabismus, where the deviation of the eye can be intermittent or constant in frequency. When the strabismus is accommodative in nature and involves an esotropia rather than an exotropia, it is termed accommodative esotropia. Accommodative esotropia results from high levels of hyperopia, an AC/A ratio (accommodative convergence/accommodation ratio that defines how much accommodative convergence occurs for a unit of accommodative response) that is too high, or the two factors working together. Onset is frequently between the ages of two and three years (Donahue 2007). The ability to do near tasks is compromised, with intermittent diplopia (double vision) and asthenopia (eyestrain) among other reported symptoms (Cotter 1997). About 10% to 20% of children with +4.0 D or more of hyperopia develop accommodative esotropia (Atkinson 1996; Dobson 1989). More recent, cross‐sectional data from the Multi‐Ethnic Pediatric Eye Disease and Baltimore Pediatric Eye Disease Studies showed that even at +2.0 D of hyperopia, there was a six‐fold increase in the odds of esotropia (Cotter 2011). About half of the children with esotropia become amblyopic according to Donahue 2007.
Description of the intervention
Hyperopia is often treated with a spectacle correction to remove or reduce the need for accommodation to view distance and near targets (Donahue 2007; Rubin 2006), and, thus, may help to prevent the development of strabismus (Rubin 2006). No other interventions have been proposed to manage hyperopic infants in an effort to prevent the development of strabismus (AOA 2008).
How the intervention might work
Treatment of hyperopia with the intention of preventing accommodative esotropia is a topic of disagreement. Using a spectacle correction to reduce the need for accommodation when fixating at is distance (i.e. reducing the accommodative effort needed to bring an image into focus) is a proposed treatment. In addition, reduced stimulation of accommodative convergence is an added benefit. The angle of existing esotropia will be reduced or perhaps eliminated. The expectation is that removing accommodative strain will allow regular binocular vision to develop during emmetropization, allowing for a decrease and eventual cessation of the spectacle correction (Rubin 2006). Although spectacle correction may be critical to prevent the development of esotropia, spectacles may prevent normal emmetropization. Atkinson 2000 found that any lag in the emmetropization of infants wearing a partial correction (undercorrection) for hyperopia at nine or 18 months had disappeared by three years, and that these children had similar refractive errors to children who were untreated. Others, however, found that children with a spectacle correction for their hyperopia did not emmetropize (Ingram 2000; Mulvihill 2000; Repka 1989). It is speculated that emmetropization is affected by the absence of accommodative demand that comes about from wearing a full spectacle correction (Birch 2005; Mutti 2009). As a result of this speculation, some ophthalmologists adopt a partial correction of the hyperopia to reduce the need for accommodation while providing some signal for emmetropization.
Why it is important to do this review
The conversion rate to amblyopia is high among children with esotropia, threatening long‐term visual health and productivity. Hyperopia presents a strain on the visual system causing symptoms such as blurred vision and asthenopia, as well as possibly adversely affecting the learning and academic growth of the highly hyperopic child. The spectacle prescription is meant to correct the hyperopia to reduce the accommodative effort required to bring images into focus. It reduces stimulation of accommodative convergence as an added benefit. Whether reduced stimulation of accommodative convergence with spectacles lowers the risk of future strabismus is an important but unanswered question. However, if we treat every infant with hyperopia with spectacles, we could be treating 80% to 90% of these children unnecessarily (Birch 2005). Because of the differing evidence regarding the effectiveness of treating these children with spectacles and the concerns about interference with emmetropization, straightforward recommendations are difficult to make. To that end, high‐quality data describing the effects, if any, of treatment with spectacles, and the level of treatment required to be effective, are necessary.
Objectives
To assess the effectiveness of prescription spectacles compared with no intervention for the prevention of strabismus in infants and children with hyperopia.
Methods
Criteria for considering studies for this review
Types of studies
We included randomized and quasi‐randomized controlled trials.
Types of participants
We included trials with children from three months old to four years old at entry, with an age of primary outcome assessment at or before seven years of age. We based the risk of development of strabismus on the criteria as defined by the included studies. Typically, the criteria include high hyperopia which is at least +2.0 D of refractive error. The trial investigators must have diagnosed hyperopia by cycloplegic retinoscopy. Other conditions that could be included were anisometropia or astigmatism. There were no gender restrictions. We excluded studies that included children with existing strabismus, amblyopia, or other ocular pathology.
Types of interventions
We included trials in which spectacle correction for any level of hyperopia greater than +2.00 D was compared with no spectacle correction. We also planned, when available, to include trials that used a sham correction in the control group and trials that had compared full hyperopic spectacle correction with partial hyperopic spectacle correction.
Types of outcome measures
Primary outcomes
-
Proportion of children with manifest strabismus, as defined by study investigators, in the spectacle correction group compared with the proportion of children with strabismus in the no treatment group after a treatment period of a minimum of three years.
Because no child started with strabismus, studies may have reported this outcome directly as the proportion of children with strabismus at the end of the follow‐up period or as the incidence of strabismus during the follow‐up period. Strabismus was commonly identified by one of the following methods: unilateral cover test, or the Hirschberg test (with or without spectacle correction), in conjunction with the 4‐D prism test for suppression or microtropia. We considered other clinically meaningful treatment periods as reported by included studies in this review.
We considered manifest strabismus as a dichotomous variable and did not attempt to stratify outcomes according to final deviation or visual acuity (VA), or whether participants wore spectacles at the time of final assessment.
Secondary outcomes
-
Amblyopia, defined as a difference of three lines of VA between eyes.
-
Stereoacuity as defined by the study using the appropriate criteria for the test chosen (i.e. Randot Stereoacuity Test or a similar measure). These were also measured after a minimum treatment period of three years. When reported from studies, we also considered how outcome results (such as strabismus and VA) were affected when accounting for compliance with spectacle correction.
-
Change in refractive error, as a measurement of the interference of emmetropization, defined as the expected change anticipated to achieve emmetropization, given the level of refractive error at baseline, both continuously and as the proportion of children who did not achieve a refractive error in the emmetropic range.
-
Quality of life.
-
Proportion of participants with inadequate VA (worse than 20/30). (This was a post‐hoc decision as an intermediate assessment of the natural development of vision as only one included trial evaluated amblyopia and stereoacuity.)
Search methods for identification of studies
Electronic searches
The Cochrane Eyes and Vision Information Specialist searched the following electronic databases for randomized controlled trials and controlled clinical trials. There were no restrictions to language or year of publication.
-
Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 12) (which contains the Cochrane Eyes and Vision Trials Register) in the Cochrane Library (searched 4 December 2018; Appendix 1).
-
MEDLINE Ovid (1946 to 4 December 2018; Appendix 2).
-
Embase.com (1947 to 4 December 2018; Appendix 3).
-
PubMed (1948 to 4 December 2018; Appendix 4).
-
Latin American and Caribbean Health Sciences Literature Database (LILACS) (1982 to 4 December 2018; Appendix 5).
-
metaRegister of Controlled Trials (mRCT) (www.controlled‐trials.com) (last searched 3 April 2014; Appendix 6).
-
US National Institutes of Health Ongoing Trials Register ClinicalTrials.gov (www.clinicaltrials.gov; searched 4 December 2018; Appendix 7).
-
World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp; searched 4 December 2018; Appendix 8).
Searching other resources
We searched the reference lists of reports from trials we identified to look for additional trials. We did not conduct manual searches of conference proceedings or abstracts specifically for this review. In the first version of the review, we also used the Science Citation Index‐Expanded database (September 2013) to identify additional studies that may have cited trials that we included in this review.
Data collection and analysis
Selection of studies
Two review authors independently reviewed titles and abstracts resulting from the literature searches, according to the inclusion criteria. We classified the records as 'definitely relevant', 'possibly relevant', or 'definitely not relevant'. After adjudication, we retrieved the full‐text reports for records classified as 'definitely relevant' or 'possibly relevant' by both review authors and then assessed the studies for inclusion, labeling each study as 'include' or 'exclude'. We did not need to contact trial authors of studies for further clarification as all studies could be included or excluded after examining the full‐text reports. We excluded studies labeled as 'exclude' by both review authors after the review of full‐texts and documented the reasons for exclusion in the Characteristics of excluded studies table. We resolved any disagreements through discussion at all stages of the study selection process.
Data extraction and management
Two review authors independently extracted data using a form based on templates developed and piloted by the Cochrane Eyes and Vision. One review author entered data into Review Manager 5 (Review Manager 2014), and a second review author verified the data entered. We resolved discrepancies in data extraction and data entry by discussion.
Assessment of risk of bias in included studies
Two review authors independently assessed the included studies for sources of bias according to the guidelines in Chapter 8 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), and resolved disagreements through discussion. We evaluated the studies for the following criteria: sequence generation and allocation concealment (selection bias), masking of participants/personnel (performance bias), masking of outcome assessors (detection bias), incomplete outcome data (attrition bias), selective outcome reporting (reporting bias), and other sources of bias. We reported our judgment for each criterion as 'low risk', 'high risk', or 'unclear risk' of bias. We contacted study investigators for the present review. In case of failure to communicate with the primary investigators, or if there is no response within four weeks, we will assess the risk of bias on the basis of the available information and will update it as more information becomes available.
-
We reported adequacy of sequence generation and allocation concealment. Methods of sequence generation that we considered to be at low risk of bias included use of random number tables, computer‐generated randomization, and coin tosses. We considered any method of allocation concealment that provided reasonable confidence that the investigators concealed the allocation sequence from participating physicians and participants (children and parents) at low risk of bias (such as centralized randomization and use of sequential opaque envelopes).
-
We assessed masking (blinding) of participants and personnel in the included studies. Although masking is not possible when spectacles are compared with no spectacles, masking is possible if the comparison of spectacles was with sham spectacles or partial spectacle correction.
-
We noted masking (blinding) of outcome assessors by study outcome or group of outcomes (e.g. primary and secondary outcomes) in the included studies.
-
For incomplete outcome data, we examined the proportion of participants lost to follow‐up, reasons for loss to follow‐up, and methods of analysis. We assessed whether follow‐up for treatment and control arms were similar and whether there were missing data for outcomes of interest. We considered studies at low risk of bias when there were no missing data or when missing data were correctly imputed and when the reasons for missing data were adequately addressed. We plan to note the method of data imputation if reported in any future included studies.
-
We assessed risk of bias for selective outcome reporting. We considered a study at low risk of bias when trial authors reported all prespecified outcomes of interest in the published report in the same manner as described in the study protocol. We considered the risk of bias to be unclear whenever the protocol was not available. Whenever the published report described different outcomes in the protocol and published report, or when the protocol was not available, different outcomes were reported in the Methods and Results section, we considered the trial as having high risk of bias.
-
We examined included studies for other sources of bias and considered studies at low risk of bias when there was no evidence of research misconduct and no potential for bias based on study methodology.
Measures of treatment effect
We calculated a summary risk ratio (RR) with corresponding 95% confidence interval (CI) for dichotomous outcomes, including the primary outcome of the presence or absence of strabismus at three years and secondary outcomes of amblyopia, stereoacuity, the presence or absence of emmetropization, and VA above a clinically meaningful cut‐point (i.e. 20/30 or worse). For continuous outcomes (e.g. change in refractive error to determine if emmetropization had occurred), we calculated mean differences (MD) with corresponding 95% CIs in changes from baseline when reported by included studies as well as the MD at a time point. For continuous outcomes, reported for spectacle compliant, spectacle non‐compliant, and control groups separately, we averaged the means and standard deviations (SD) to calculate effect estimates for the as‐randomized analyses (spectacle compliant and non‐compliant versus controls).
Unit of analysis issues
The unit of analysis was the child, as strabismus is a malfunction of the binocular system. Cross‐over trials are not included in this review because the status of the condition under study may change following an intervention, making a second intervention meaningless.
Dealing with missing data
We did not contact primary authors of included studies because no relevant data were missing. If any data were missing, such as SDs and intention‐to‐treat data, we would have contacted primary authors. If data were missing, we would not have imputed them, but analyzed them as available.
Assessment of heterogeneity
We assessed clinical and methodologic heterogeneity by examining variations in participant characteristics, inclusion/exclusion criteria, and methods of assessment of primary and secondary outcomes. We calculated the I2 statistic (%) to determine the percentage of variation in effect estimates due to heterogeneity and not chance; a value above 50% suggested substantial statistical heterogeneity. We also examined the result of the Chi2 test for heterogeneity and the degree of overlap in CIs of included studies. Poor overlap also may suggest heterogeneity.
Assessment of reporting biases
The small number of studies included in each meta‐analysis prevented a meaningful interpretation of funnel plots. If studies are added to the meta‐analyses in the future updates, we will examine funnel plots to assess small‐study effects, which could be due to reporting biases. We will use this method in conjunction with study characteristics or other factors that may contribute to asymmetry of the funnel plot.
Data synthesis
In the protocol of this review, we stated that we would not combine results in meta‐analysis when the I2 statistic suggested substantial statistical heterogeneity (i.e. I2 greater than 50%) (Jones 2009). However, because we considered the included trials were similar clinically and methodologically, we combined the results in meta‐analyses for strabismus and VA outcomes. We used a random‐effects model for all analyses.
Subgroup analysis and investigation of heterogeneity
We further evaluated heterogeneity through subgroup analyses of children with high levels of hyperopia (+3.50 D or greater) at baseline. We may include additional subgroup analyses with strictly hyperopia versus hyperopia and additional risk factors as we include new studies in review updates.
Sensitivity analysis
We conducted analyses based on the available‐case data for participants as randomized (assigned treatment group). We will consider the impact of excluding industry‐funded studies and unpublished studies if we include such studies in review updates.
Summary of findings and assessment of the certainty of the evidence
We summarized the findings of the review based on the guidelines in Chapters 11 and 12 of the Cochrane Handbook for Systematic Reviews of Interventions (Schünemann 2011a; Schünemann 2011b). We judged the confidence we had in the evidence for each outcome using the GRADE Working Group approach. Using this approach, we classified the certainty of evidence for each outcome of this review as 'high', 'moderate', 'low', or 'very low' and documented reasons for our judgments.
Results
Description of studies
We presented studies included in this review in the Characteristics of included studies table. We described excluded studies in the Characteristics of excluded studies table.
Results of the search
The 2014 version of this review identified 401 records through electrical searches (Jones‐Jordan 2014). Of 14 records that were reviewed in full‐text, we excluded five with reasons, and included nine records of four trials (Atkinson 1996; Hyperopia Treatment Study 1; Ingram 1985; Ingram 1990). An updated search in December 2018 resulted in 89 additional records after removal of duplicates. After assessing titles and abstracts for eligibility, five records were identified for full‐text screening. Two records of one trial were the same study as previously included as a protocol (Hyperopia Treatment Study 1), and three records of two trials were excluded with reason (NCT00574717; Pediatric Eye Disease Investigator Group 2016; Characteristics of excluded studies table). In summary, the updated search yielded results from one study that had been identified as a protocol in the last version of this review (Figure 1). This updated review contains four included studies.
Study flow diagram as of 4 December 2018.
Included studies
Participant selection
Three included trials enrolled children beginning at six and up to and including 12 months of age (Atkinson 1996; Ingram 1985; Ingram 1990), with the remaining trial including children from 12 months up to, but not including, 36 months of age (Hyperopia Treatment Study 1). There were 985 children enrolled across all four trials. To account for the broad inclusion criteria with respect to minimum eligible hyperopia levels, which ranged from +2.00 D in both meridians (Ingram 1985), +4.00 D or more in any meridian (Atkinson 1996; Ingram 1990), to +3.00 D to +6.00 D spherical equivalent (Hyperopia Treatment Study 1), we conducted prespecified subgroup analyses in which we analyzed treatment outcomes for children with hyperopia less than +3.50 D and hyperopia +3.50 D or more separately. This analysis made it possible to evaluate treatment effects in children within a similar range of hyperopia at baseline.
Interventions
All trials included in this review assigned children to receive spectacle correction or no spectacle correction. Table 1 provides a description of the parameters used for prescribing spectacle correction that differed between studies. Trial investigators used a consistent prescription of 2 D less than the participant's current refraction in two trials (Ingram 1985; Ingram 1990). In another trial, spectacle correction was influenced to a certain degree by the amount of hyperopia (Atkinson 1996), and in the remaining trial, the correction was considered partial plus, a correction by 1.0 D plus correction for astigmatism. Three studies were similar in their follow‐up protocols (every three to six months), as well as referrals for strabismus treatment should an incident case have appeared. In these trials, investigators modified spectacle prescriptions as necessary in response to refractive error changes. The remaining trial scheduled follow‐up visits at six‐month intervals at which they were assessed for deterioration (Hyperopia Treatment Study 1). Deterioration was defined as presence of manifest strabismus, distance VA below age normal values, loss of 2 or more logMAR lines of vision if VA was 20/25 or worse in the better‐seeing eye or 3 or more logMAR lines if VA was 20/20 or better in the better seeing eye, stereoacuity at near below age normal values, or non‐protocol treatment received in the absence of meeting any other deterioration criteria. If esotropia was present, then spectacles were prescribed. Spectacles were not undercorrected for hyperopia by more than 1.0 D, had full correction for anisometropia, and correction for astigmatism within 0.5 D of full correction. Additional treatment was allowed at the investigator discretion.
| Study | Spectacle treatment method |
| Sphere: 1.00 D less than the least hyperopic meridian with no prescription given for < 1.50 D Cylinder: < 2 years old – half of the astigmatic error over 2.50 D; 2–3.5 years – half of the astigmatic error; > 3.5 years – full astigmatic error | |
| Each meridian minus 2.00 D | |
| Each meridian minus 2.00 D | |
| Partial plus: glasses with sphere cut symmetrically by 1.0 D from cycloplegic refraction and full astigmatism |
D: diopter.
Outcomes
Three trials reported using the cover test to assess the presence of strabismus (assumed to be unilateral cover test) (Atkinson 1996; Hyperopia Treatment Study 1; Ingram 1990), with one trial also using the prism and alternate cover test (Hyperopia Treatment Study 1). Children were between three and four years of age at the end of three of these trials. We considered that the methods used to measure strabismus were sufficiently consistent across the included trials to allow quantitative summary meta‐analyses of these outcomes. One trial also assessed the proportion of children with strabismus at the end of three years' follow‐up (Hyperopia Treatment Study 1), so we conducted a separate analysis for strabismus for this trial.
Only one trial measured amblyopia (Hyperopia Treatment Study 1). This trial also assessed stereo acuity using the Randot Preschool Stereoacuity Test.
Three trials evaluated emmetropization (Atkinson 1996; Hyperopia Treatment Study 1; Ingram 1990). The trials used different methods to determine whether the child's vision had emmetropized, which may not necessarily have measured the actual developmental changes in the eye, and effect estimates may not have been comparable across trials. One trial recorded the mean refractive error at baseline and follow‐up in both "fixing eyes" and "non‐fixing eyes", and set a cut‐point of greater than +3.5 D in any meridian to determine whether emmetropization had not occurred (Ingram 1990). Another trial analyzed the change in the most hyperopic meridian, which was not always the same at each follow‐up examination (Atkinson 1996). The last trial determined emmetropization in two ways (Hyperopia Treatment Study 1). They compared the proportion of children who did not achieve a refractive error in the emmetropic range after three years, and the difference in spherical equivalent refractive error in both the more and less hyperopic eye between baseline and three years' follow‐up.
One trial assessed VA using Cambridge Crowding Cards with failure defined as worse than 20/40 (i.e. 6/12) (Atkinson 1996). Two trials used the Sheridan Gardiner test (Atkinson 1996; Ingram 1990), one trial used the Snellen test (Ingram 1990), and one trial used the Amblyopia Treatment Study single‐surround HOTV VA testing protocol (Hyperopia Treatment Study 1). All trials assessed VA at the last study visit; this visit was variable in three trials (Atkinson 1996; Ingram 1985; Ingram 1990), and after three years of follow‐up in the fourth (Hyperopia Treatment Study 1), so we included all trials in a meta‐analysis.
Outcome examiners in two trials determined compliance with treatment (Ingram 1985; Ingram 1990). Investigators of one trial considered children who wore the prescribed spectacles for greater than 50% of waking hours as compliant based on parent interviews and questionnaires (Atkinson 1996), while those in the remaining trial asked parents to report on children's use of spectacles (Hyperopia Treatment Study 1).
None of the trials measured quality of life in these children or their parents.
Funding sources
One trial was funded by regional sources, the Medical Research Council of Great Britain and a grant from the East Anglia Regional Health Authority (Atkinson 1996), and one by the National Eye Institute, National Institutes of Health (Hyperopia Treatment Study 1). Ingram 1985 and Ingram 1990 did not report funding sources.
Excluded studies
We reviewed and excluded two studies at this update totaling seven with previously excluded five studies (Characteristics of excluded studies table). One study did not investigate the use of spectacle correction as an intervention (Althaus 1994), and one study included older participants (Pediatric Eye Disease Investigator Group 2016). The other five studies were not randomized or quasi‐randomized trials (Anker 2004; MacEwen 2008; NCT00574717; Nischal 2008; Roth 1989).
Risk of bias in included studies
Figure 2 presents summary information on the risk of bias for the trials included in this review.
Risk of bias summary: review authors' judgments about each risk of bias item for each included study.
Allocation
We judged Ingram 1990 at low risk of bias for random sequence generation because the study investigators used a "random number table" to generate the random sequence. We also judged the Hyperopia Treatment Study 1 at low risk of bias for random sequence generation because the Jaeb Center prepared the stratified blocked random sequence by computer. We judged Atkinson 1996 at high risk of bias because some of the infants were alternately assigned to the treated or untreated group. Ingram 1985 did not specify the method for randomization, therefore, we judged the risk to be unclear.
None of the four trials provided sufficient details describing how participants were allocated to treatment groups and we judged them to have an unclear risk of bias for allocation concealment.
Masking of participants and personnel (performance bias)
All studies compared spectacles versus no spectacles. Because no sham or control spectacles were used, we judged performance bias as high in all the included studies.
Masking of outcome assessors (detection bias)
Three trials did not address masking of people who assessed VA and strabismus and were thus at unclear risk of bias. Examiners were masked in the Hyperopia Treatment Study 1 trial and so this trial was at low risk of detection bias.
Incomplete outcome data
We judged three of the included trials at high risk of bias for incomplete outcome data. Atkinson 1996 did not adequately outline the number of participants from the baseline visit onward and the numbers reported in the results were inconsistent among analyses; thus, the data available did not allow us to determine the number of participants who dropped out. Ingram 1990 did not clearly identify participants allocated to the treatment and no treatment groups, and was not specific about the participants dropping out. Ingram 1985 did not specify how many participants were allocated to each group or the number of participants lost to follow‐up according to treatment group. The study authors reported 149 eligible children did not enter the study but did not explain why. In Hyperopia Treatment Study 1, 24 children did not complete the three‐year primary outcome examination. However, the protocol prespecified that the primary outcome would be analyzed using modified intention to treat without adjustment for missing values. A secondary analysis was completed using multiple imputation to account for missing values. We judged this trial to have low risk of bias.
Selective reporting
We judged two trials at unclear risk of bias for selective reporting because we did not identify study protocols (Atkinson 1996; Ingram 1990). We judged Ingram 1985 at high risk of bias due to a change in the study outcome because of concerns regarding the ability to measure VA and amblyopia in 3.5 year olds correctly. We judged the Hyperopia Treatment Study 1 trial at low risk of bias because all outcomes that were reported in the protocol were reported in the publication.
Other potential sources of bias
We did not identify other potential sources of bias for the four trials.
Effects of interventions
Strabismus
All four trials contributed data to conduct as‐randomized analyses for the incidence of strabismus over a period of three years. Three trials reported available data only, comprising 674 children and not accounting for 181 children (21%) with missing data (Atkinson 1996; Ingram 1985; Ingram 1990). The reason for missing data was mainly due to dropout or participants. The fourth trial contributed data from 130 children as determined using a Kaplan Meier survival analysis and these 130 children were included in the meta‐analysis (Hyperopia Treatment Study 1). This trial also reported the presence of strabismus at three years' follow‐up, including 106/130 children originally enrolled in the trial.
When we combined the four trials (804 children) that measured incidence of strabismus into a summary meta‐analysis based on as‐randomized data, spectacle correction led to a 35% reduction in the risk of developing strabismus up to three years of age compared with no correction (RR 0.65, 95% CI 0.41 to 1.02; I2 = 53%; Analysis 1.1). The RR for the subgroup of 615 children with hyperopia +3.50 D or greater (using a subset of children from Ingram 1985 and children from the remaining studies) was 0.70 (95% CI 0.44 to 1.14; I2 = 55%; Analysis 1.1). We have very low confidence in these results due to high risk of bias, imprecision, and inconsistency.
When looking at the presence of strabismus at the end of three years of follow‐up reported in Hyperopia Treatment Study 1, the proportion of children with manifest strabismus in the spectacle group (5/53) and in the control group (5/53) were identical. This finding agrees with the lack of evidence for an effect of spectacles on strabismus as reported looking at the incidence of strabismus in the previous three years (RR 1.00 95% CI 0.31 to 3.25; Analysis 1.2). We have very low confidence in this result due to risk of bias and imprecision.
Amblyopia
One trial reported the presence of amblyopia (Hyperopia Treatment Study 1). Amblyopia was present at three‐year follow‐up for 7/53 children in the spectacle group and 9/53 children in the control group (RR 0.78 95% CI 0.31 to 1.93; Analysis 1.3). Because this result was from a single small trial, we have very low confidence in the findings (high risk of bias, imprecision).
Stereoacuity
One trial assessed stereoacuity in 106 children at the end of three years' follow‐up using the Randot Preschool Stereoacuity test (Hyperopia Treatment Study 1). Children whose stereoacuity was below age normal values were considered failures. There were six stereoacuity failures in 53 children in the spectacle correction group and 16 failures among the 53 children in the control group (RR 0.38, 95% CI 0.16 to 0.88; Analysis 1.4). We have very low confidence in this result because it was derived from a single study with high risk of bias and imprecision.
Emmetropization
Three trials reported emmetropization (Atkinson 1996; Hyperopia Treatment Study 1; Ingram 1990). Given the variety of methods used to evaluate emmetropization, we could not conduct summary meta‐analyses of this outcome including all trials. Instead, we have provided a narrative summary of the results from three of the trials individually.
When dichotomized with refractive error +3.5 D or greater at follow‐up, indicating emmetropization had not occurred, one trial (287 children) showed a RR of 1.32 (95% CI 0.97 to 1.80) when comparing 60/144 children in the spectacle group with 45/143 children in the control group for which emmetropization had not occurred (Ingram 1990). When evaluating the mean change in refractive error from baseline to final follow‐up (mean of 3.2 years), there was an MD of 0.22 D (95% CI –0.20 to 0.64) in the "fixing eye" between 100 children in the spectacle group (mean change –1.12 D, SD 1.65) and 89 children in the control group (mean change –1.34 D, SD 1.30) among children without strabismus at the follow‐up visit. Among children with strabismus, the MD was –0.24 D (95% CI –0.96 to 0.48) between 47 children in the spectacle group (mean change –0.40 D, SD 2.13) and 53 children in the control group (mean change –0.16 D, SD 1.40) (Ingram 1990).
The second trial reported no difference between the spectacle group and control group after accounting for compliance with treatment (Atkinson 1996). At three years of age, the refractive error in the most hyperopic meridian was +3.4 D in the spectacle group and +3.1 D in the control groups. Using SDs inferred in the text describing the results for each group, the difference in the mean refractive error between 44 children in the spectacle group (mean +3.4 D, SD 1.4) and 37 children in the control group (mean +3.1 D, SD 1.5) was 0.3 D (95% CI –0.34 to 0.94). The trend was similar when we accounted for compliance with a refractive error of +3.3 D in the spectacle compliant group. The investigators reported a statistically non‐significant difference in refractive error at three years for both of the above comparisons.
The remaining trial reported emmetropization in two ways (Hyperopia Treatment Study 1). First, they reported it as the mean change in spherical equivalent from baseline to the three‐year follow‐up visit by the more or less hyperopic eye. The difference in spherical equivalent refractive error between groups was 0.15 (95% CI –0.51 to 0.84) for the more hyperopic eye and 0.22 (95% CI –0.43 to 0.86) in the less hyperopic eye. Second, they reported the proportion of children who did not achieve a refractive error in the emmetropic range at the three‐year follow‐up visit. Three of 53 children in the spectacle group and 4/53 in the control group failed to present with refraction in the emmetropic range at the three‐year follow‐up visit (RR 0.75, 95% CI 0.18 to 3.19; Analysis 1.5). The confidence in this finding is low due to risk of bias and imprecision.
Quality of life
None of the studies reported quality of life.
Visual acuity
All trials reported VA at visits up to the age of three to four years or at the end of three years of follow‐up. Investigators of three trials assessed VA by considering vision worse than 20/30 (i.e. 6/9) to be inadequate (Atkinson 1996; Ingram 1985; Ingram 1990), while in the Hyperopia Treatment Study 1, VA worse than age‐adjusted values at the three‐year follow‐up visit was considered inadequate. Among these four studies (770 children), there was unclear evidence of an effect of spectacles on VA compared with no spectacles (RR 0.87, 95% CI 0.64 to 1.18; I2 = 0%; Analysis 1.6). If we exclude those children who had less than +3.50 D of hyperopia at baseline from Ingram 1985, the summary meta‐analysis (three trials, 581 children) revealed an RR of 0.84 (95% CI 0.59 to 1.20; I2 = 15%; Analysis 1.6). We judged this evidence as very low, being downgraded for high risk of bias and imprecision.
Discussion
Summary of main results
We included four trials in this review from which 804 hyperopic children provided follow‐up data to determine the effects of spectacle correction for preventing strabismus. Three trials allocated infants between the ages of six and 12 months to a spectacle treatment group or an untreated group and evaluated the incidence of strabismus and assessed VA and emmetropization when the children were between three and four years of age. The remaining trial included 130 children from ages of 12 to less than 36 months and provided data on the incidence of strabismus and VA based on age normal values between the ages of four and five years. This trial also provided data on the presence of strabismus, amblyopia, spherical equivalent within emmetropic range, and failure to meet age‐based norms for stereoacuity in the same time frame as above. Based on our assessment of these trials, there is unclear evidence that spectacle correction is associated with a lower risk of developing strabismus or preventing inadequate VA in infants or children with hyperopia. There is some indication that spectacles provide a benefit in achieving stereoacuity, although this was reported in only a single study. Three studies considered the potential adverse effect of spectacle treatment, the inhibition of emmetropization. The results from one trial suggested that spectacles impede emmetropization (as defined by an increase in risk of remaining hyperopic) (Ingram 1990); a second trial reported no difference in the rate of refractive error change (Atkinson 1996); and a third trial reported no difference in the spherical equivalent that would indicate emmetropization at the end of follow‐up (at age four to five years) (Hyperopia Treatment Study 1). Although children who were allocated to the spectacle group were less likely to develop strabismus across the included studies, this may have been a chance finding, or due to bias. Due to high risks of bias and poor reporting of the majority of included trials, the true effect of spectacle correction for hyperopia on strabismus is still uncertain.
Overall completeness and applicability of evidence
Clinically, the four included studies were not substantially heterogeneous. For presence of strabismus, although there appeared to be some statistical heterogeneity across trials, the CIs of individual studies overlapped and the I2 value was around our prespecified threshold of 50% (I2 = 53%). Thus, we combined the findings in a meta‐analysis. For VA worse than 20/30, there was no statistical heterogeneity (I2 = 15%). We combined the findings in a meta‐analysis for presence of strabismus at three to four years of age and VA worse than 20/30. There was additional methodologic variation in the way investigators of trials evaluated emmetropization, preventing meta‐analysis of this outcome. In trials, the amount of refractive error change that occurred seemed to result in incomplete emmetropization (i.e. the resulting refractive error had not reached a 'normal' level) in some children.
It is important to consider children similar in risk and possible etiology because highly hyperopic children are thought to be less likely to emmetropize (Mutti 2009), and therefore are likely to benefit from treatment. In subgroup analyses, we considered only those children with at least +3.50 D hyperopia at baseline. The subgroup analyses did not show that wearing spectacles decreased the risk of developing strabismus or of poor VA in children who were highly hyperopic.
One potential issue when considering these trials is the possible impact the time of treatment initiation may have had. Ingram 1985 began with infants who were one year old, but in a subsequent study (Ingram 1990), treatment initiation was moved to six months of age because they suspected the sensitive period was earlier. Atkinson 1996 enrolled infants between six and eight months of age and the Hyperopia Treatment Study 1 enrolled children between one and two years of age. Therefore, comparing varying ages may be obscuring the possibility that a sensitive period may exist.
The trials used similar treatments (spectacles) and controls (untreated) and the amount of correction was reasonably consistent across all trials (Table 1). Both Ingram 1985 and Ingram 1990 used a +2.00 D decrease in the refractive correction for spectacle prescription as opposed to the +1.00 D decrease in refractive correction used by the other trial (Atkinson 1996), while the Hyperopia Treatment Study 1 provided partial plus hyperopic correction (i.e. sphere cut symmetrically by 1.00 D and full astigmatism correction).
In general, the studies did not consider the level of astigmatism. Current literature suggests that the amount of infant astigmatism seems to have little to no effect on emmetropization of spherical equivalent refractive error (Ehrlich 1997; Mutti 2004).
Assessing treatment compliance is difficult to ascertain given the potential for recall bias. Determining what constitutes compliance is also a problem. It is possible that there is a certain amount of time that spectacles should be worn to have a clinically meaningful effect. Each study used a different assessment of compliance. Ingram 1990 simply stated that "some children obviously wore the glasses consistently, but it was apparent that some wore them irregularly and others not at all" as their definition of compliance. It appears that Ingram 1985 used something similar to classify participants as compliant. Atkinson 1996 questioned the parent and classified a child as compliant whenever the parent indicated that the child wore the spectacles at least 50% of the time, while the Hyperopia Treatment Study 1 measured compliance by parent report of use of spectacles at least 75% of the time. One option for a future trial would be one that assesses treatment groups assigned to varying wearing times (e.g. four hours per day, eight hours per day, 12 hours per day) compared with a no correction group to allow for the determination of an effect of the amount of time correction was worn.
In terms of the outcomes, all trials used similar assessments at a similar time, so comparing them was reasonable; however, the data contributing to this review, given the potential attrition bias mentioned above, do not provide a reliable assessment of the effect of spectacle correction. Only one study report included any information regarding race, gender, and family history of amblyopia or strabismus (Hyperopia Treatment Study 1).
Quality of the evidence
We observed several potential biases in the design (no use of a proper randomization sequence and no masking of those who assessed treatment outcomes) and conduct (large proportion of participants lost to follow‐up as well as incomplete compliance with the intervention) in three of the included trials (Atkinson 1996; Ingram 1985; Ingram 1990), and biases associated with lack of masking and possible allocation concealment in the fourth trial (Hyperopia Treatment Study 1). Three of the four included trials had a high degree of uncertainty in the presence of potential biases due to insufficient descriptions of important methodologic design issues. One trial used alternate assignment for participants to treatment groups, so we judged the risk of bias as high. Two trials specified the methods of sequence generation, so we judged the risk as low and another trial did not specify the method for randomization. None of the three trials indicated how treatment assignments were allocated to ensure investigators and study participants did not have prior knowledge of their treatment assignment. We judged all trials at high risk of performance bias as they all compared spectacles versus no treatment. Only one trial specified masking of people assessing VA and strabismus (Hyperopia Treatment Study 1), but the risk of detection bias remained unclear in the other three trials. The Hyperopia Treatment Study 1 was also stopped early due to slow recruitment. We considered three of the four trials included in this review to be at a high risk of bias for incomplete outcome data (Figure 2). Due to the high loss to follow‐up in all trials and lack of details regarding missing participant data, the data were not complete and do not provide an accurate estimate of the overall treatment effect of spectacle correction for preventing strabismus (i.e. very low certainty of evidence) (summary of findings Table for the main comparison). Added to the high risk of bias is the imprecision observed across all trials and meta‐analytic findings, further reducing the confidence we have in these results.
Potential biases in the review process
Two review authors independently reviewed titles, abstracts, and full‐text reports of potentially eligibly trials, and extracted data and assessed risk of bias for all trials included in this review, which should have minimized review bias. During the review process, we added a post‐hoc secondary outcome for VA. We are aware of no other potential biases in the review process.
Agreements and disagreements with other studies or reviews
To our knowledge, there are no other systematic reviews on this subject. One retrospective, observational study of hyperopic children identified in a preschool screening found no statistically significant difference between the percentage of children who developed amblyopia among children who received some type of spectacle correction and children who did not (21% with spectacle correction versus 38% with no spectacle correction); however, the study authors concluded the results were consistent with a benefit of spectacle correction on reducing amblyopia risk. However, only 16 children received no treatment so the sample size was insufficient to support inferences (Colburn 2010). Anker and coworkers in a follow‐up study to Atkinson's First Cambridge Study, reported on a non‐randomized study of spectacle correction in children with hyperopia of +4.0 D or greater. Correction did not reduce the occurrence of strabismus after three years, but did seem to improve VA over no treatment (Anker 2004). Current preferred practice guidelines show uncertainty with regard to when to prescribe spectacles for hyperopic children due to the lack of empirical data. The American Optometric Association Optometric Clinical Practice Guidelines suggest that in the absence of amblyopia or strabismus, practitioners begin treating hyperopia in children from birth to 10 years of age at levels of hyperopia of +5.0 D or greater, with consideration made for other coexisting factors that are relevant in the clinician's judgment. They recommend a partial prescription with monitoring (AOA 2008). The American Academy of Ophthalmology Pediatric Ophthalmology/Strabismus Panel has issued age‐tiered guidelines for prescribing correction for hyperopia. In children under one year of age with no manifest deviation, they recommend correction beginning at +6.0 D of hyperopia. For children ages one to two years, they recommend prescribing spectacles for hyperopia of +5.0 D or greater, and for children ages two to three years of age, they recommend refractive correction for +4.50 D and greater of hyperopia (AAO 2012).
Leat presented several recommendations for prescribing spectacle correction based upon the literature, mainly the studies cited in this review, evaluating potential treatment effects in hyperopic children (Leat 2011). Based on the expected distribution of refractive error at various ages, the trial author recommended partial correction when the refractive error fell outside the normal range of the age group. After one year of age, a partial prescription was suggested starting at +3.50 D of hyperopia. Ciner recommended prescribing at greater than +2.0 D for children less than five years of age (Ciner 1990), while and Marsh‐Tootle and Frazier suggested a prescription for those greater than +3.0 D up to the age of three years (Marsh‐Tootle 2006).
Based upon the guidelines, recommendations, and the results of this review, there is uncertainty in the benefit of spectacle correction and the preferred amount of correction, which is another area that warrants investigation to be able to assess the efficacy of spectacle treatment for the prevention of strabismus. There is also some variation in the level of hyperopia at which to prescribe spectacle correction, although the guidelines agree that there is a level that is 'high' hyperopia beyond which refractive error is unlikely to resolve on its own.
Study flow diagram as of 4 December 2018.
Risk of bias summary: review authors' judgments about each risk of bias item for each included study.
Comparison 1 Spectacle correction versus no spectacle correction, Outcome 1 Incidence of strabismus up to 3–4 years of age.
Comparison 1 Spectacle correction versus no spectacle correction, Outcome 2 Proportion of children with manifest strabismus.
Comparison 1 Spectacle correction versus no spectacle correction, Outcome 3 Proportion of participants with amblyopia.
Comparison 1 Spectacle correction versus no spectacle correction, Outcome 4 Proportion of participants with inadequate stereoacuity.
Comparison 1 Spectacle correction versus no spectacle correction, Outcome 5 Proportion of participants who did not achieve a refractive error in the emmetropic range.
Comparison 1 Spectacle correction versus no spectacle correction, Outcome 6 Visual acuity worse than 20/30 up to 3–4 years of age.
| Spectacle correction compared with no spectacles for infants or children with hyperopia | ||||||
| Patient or population: infants or children with hyperopia Settings: pediatric eye clinics Intervention: spectacle correction Comparison: no spectacles | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect | No of participants | Certainty of the evidence | Comments | |
| Assumed risk | Corresponding risk | |||||
| No spectacles | Spectacles | |||||
| Incidence of strabismus up to 3–4 years of age | 234 per 1000 | 152 per 1000 | RR 0.65 (0.41 to 1.02) | 804 (4 studies) | ⊕⊝⊝⊝ Very lowa,b,c | — |
| Proportion of children with strabismus at 3 years' follow‐up | 94 per 1000 | 94 per 1000 | RR 1.00 (0.31 to 3.25) | 106 children | ⊕⊝⊝⊝ Very lowa,c | — |
| Proportion of children with amblyopia at 3 years | 170 per 1000 | 133 per 1000 (53 to 328) | RR 0.78 (0.31 to 1.93) | 106 children | ⊕⊝⊝⊝ Very lowa,c | — |
| Proportion of children with inadequate stereoacuity at 3 years | 302 per 1000 | 114 per 1000 | RR 0.38 (0.16 to 0.88) | 106 children | ⊕⊝⊝⊝ Very lowa,c | — |
| Proportion of children without refractive error in the emmetropization range at 3 years | 75 per 1000 | 100 per 1000 (14 to 239) | RR 0.75 (0.18 to 3.19) | 106 children | ⊕⊝⊝⊝ Very lowa,c | Emmetropization was also reported as:
|
| Visual acuity worse than 20/30 at 3–4 years of age | 183 per 1000 | 159 per 1000 | RR 0.87 (0.64 to 1.18) | 770 (4 studies) | ⊕⊝⊝⊝ | — |
| *The basis for the assumed risk (e.g. the mean 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). CI: confidence interval; D: diopter; n: number of participants; RR: risk ratio; SD: standard deviation. | ||||||
| GRADE Working Group grades of evidence | ||||||
| aDowngraded one level for risk of bias because studies were at high or unclear risk of bias for allocation concealment and high risk of bias for masking. | ||||||
| Study | Spectacle treatment method |
| Sphere: 1.00 D less than the least hyperopic meridian with no prescription given for < 1.50 D Cylinder: < 2 years old – half of the astigmatic error over 2.50 D; 2–3.5 years – half of the astigmatic error; > 3.5 years – full astigmatic error | |
| Each meridian minus 2.00 D | |
| Each meridian minus 2.00 D | |
| Partial plus: glasses with sphere cut symmetrically by 1.0 D from cycloplegic refraction and full astigmatism | |
| D: diopter. | |
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Incidence of strabismus up to 3–4 years of age Show forest plot | 4 | 804 | Risk Ratio (M‐H, Random, 95% CI) | 0.65 [0.41, 1.02] |
| 1.1 Children with hyperopia < 3.5 D at ages 6–12 months | 1 | 189 | Risk Ratio (M‐H, Random, 95% CI) | 0.39 [0.14, 1.05] |
| 1.2 Children with hyperopia ≥ 3.5 D at ages 6–12 months | 4 | 615 | Risk Ratio (M‐H, Random, 95% CI) | 0.70 [0.44, 1.14] |
| 2 Proportion of children with manifest strabismus Show forest plot | 1 | Risk Ratio (IV, Fixed, 95% CI) | Totals not selected | |
| 3 Proportion of participants with amblyopia Show forest plot | 1 | Risk Ratio (IV, Fixed, 95% CI) | Totals not selected | |
| 4 Proportion of participants with inadequate stereoacuity Show forest plot | 1 | Risk Ratio (IV, Fixed, 95% CI) | Totals not selected | |
| 5 Proportion of participants who did not achieve a refractive error in the emmetropic range Show forest plot | 1 | Risk Ratio (IV, Fixed, 95% CI) | Totals not selected | |
| 6 Visual acuity worse than 20/30 up to 3–4 years of age Show forest plot | 4 | 770 | Risk Ratio (M‐H, Random, 95% CI) | 0.87 [0.64, 1.18] |
| 6.1 Children with hyperopia < 3.5 D at ages 6–12 months | 1 | 189 | Risk Ratio (M‐H, Random, 95% CI) | 1.35 [0.31, 5.86] |
| 6.2 Children with hyperopia ≥ 3.5 D at ages 6–12 months | 4 | 581 | Risk Ratio (M‐H, Random, 95% CI) | 0.84 [0.59, 1.20] |
