Randomised trial of wide-field guided PRP for diabetic macular oedema treated with ranibizumab

Diabetic macular oedema (DMO) is effectively treated with ranibizumab but multiple injections are required. Where there is also peripheral ischaemia, it has been promoted that targeted panretinal photocoagulation (PRP) may reduce the number of injections.

Patients with optical coherence tomography confirmed DMO and Ultra-widefield Fundus Fluorescein Angiography confirmed peripheral retinal ischaemia were randomised to PRP plus ranibizumab or ranibizumab monotherapy. After three injections, repeat injections were given until the visual acuity was stable and the macula was dry. Re-treatment was given if there was a drop of visual acuity and/or a recurrence of intra-retinal fluid. The primary outcome was the number of repeat injections required after the first 6 months up until 1 year.

There were 49 patients, 25 in the ranibizumab only group and 24 in the ranibizumab + PRP group recruited at seven UK sites. The average number of injections in the ranibizumab-only arm was 6.84 over 1 year and 2.52 between months 6 and 12. The average number of injections in the combined arm was 6.67, with the number of injections in the second 6 months 1.92. For the primary outcome, comparing the number of 6- to 12-month injections, the result was not statistically significant (p = 0.33).

The addition of targeted PRP to areas of non-perfusion in a patient with DMO does not reduce the number of injections required in the first year. It seems most likely that local VEGF at the macula is the main cause of DMO.