Title

On the recommendation of a clinical peer reviewer we changed the title of this review from "laser photocoagulation for diabetic retinopathy" to "laser photocoagulation for proliferative diabetic retinopathy". The reviewer felt that clinicians seeing the broader title would expect to see diabetic macular oedema (DMO) included in this review but this is specifically excluded as there is a separate review looking at laser for DMO (Jorge 2013).

Outcomes

We changed 'distance corrected near visual acuity' to 'near visual acuity'. We did not find any data on near visual acuity, either distance corrected or not.

We moved the outcome 'severe visual loss' out of adverse effects and further up the list, refecting the use of this outcome generally as a measure of effect rather than an adverse effect as originally defined in our protocol. We considered this outcome at one year follow‐up as for the other effectiveness outcomes (and not, as originally planned, within three months of treatment).

We removed the outcome 'secondary choroidal neovascularisation' for future updates. This outcome is more of a concern after treatment for diabetic macular oedema. We did not find any data on this outcome.

Measures of effect

We planned to calculate the risk ratio for dichotomous variables where the event risk was greater than 10%, the odds ratio for dichotomous variables where the event risk was less than 10% and for very rare events (less than 1%) the Peto odds ratio. In fact for most analyses the event risk in the control group was greater than, or approximately, 10% and we felt that it would be confusing to report an odds ratio for only one outcome (severe visual loss) where the event rate was 4%. We have therefore only used the risk ratio as the measure of effect for dichotomous variables. This decision has not affected the conclusions drawn. For the outcome of severe visual loss the reported risk ratio was 0.46 (95% CI 0.24 to 0.86) and this is similar to the odds ratio of 0.40 (95% CI 0.18 to 0.88).

Data synthesis

We planned that, in cases of substantial heterogeneity, for example differences in direction of effect, or where the I² statistic was greater than 50% and the Chi² statistic less than 0.1, such that the pooled result did not summarize the individual trial results adequately, we would not provide a pooled estimate, unless visual inspection of the forest plot indicated it might be appropriate to do so (for example, if all effect estimates were in the same direction). For one analysis, Analysis 1.1, the effect estimates were reasonably close to 1 and we report a pooled estimate even though the effect estimates were not in the same direction.