Purpose: To compare the effectiveness of subthreshold grid laser treatment (SGLT) with an infrared micropulse diode laser with that of threshold grid laser treatment (TGLT) for macular edema secondary to branch retinal vein occlusion (BRVO).
Design: Randomized clinical trial.
Participants: Thirty-six patients (36 eyes) were randomized either to infrared SGLT (17 eyes) or to krypton TGLT (19 eyes).
Methods: Complete ophthalmic examinations, including determination of visual acuity (VA) with Early Treatment Diabetic Retinopathy Study charts, optical coherence tomography (OCT), and fluorescein angiography, were performed at the time of the study entry and at 6-month intervals, with a planned follow-up of 24 months.
Main outcome measures: Primary: decrease in mean foveal thickness (FT) on OCT. Secondary: changes of the total macular volume (TMV) over the follow-up, proportion of eyes that gained at least 10 letters (approximately > or =2 lines of VA gain) at the 12- and 24-month examinations, and timing of macular edema resolution.
Results: Changes in mean FT and TMV from the initial values were statistically significant for TGLT from the 6-month examination (P<0.001) and for SGLT from the 12-month examination (P<0.001). After 1 year, there was no difference in mean FT and TMV between the 2 groups. At the 12-month examination, 10 patients of the SGLT group (59%) and 11 of the TGLT group (58%) gained at least 10 letters (2 lines) in VA. At the 24-month examination, this gain was achieved by 11 patients (65%) of the SGLT group and 11 (58%) of the TGLT group. Moreover, at the 24-month examination 59% and 26% gained 3 lines in the SGLT and TGLT groups, respectively.
Conclusions: Resolution of macular edema and VA improvement are similar to those obtained with conventional TGLT, but SGLT is not associated with biomicroscopic and angiographic signs. A multicenter randomized clinical trial would be needed to ascertain the real efficacy and the most appropriate settings of SGLT for macular edema secondary to BRVO.