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Subthreshold Grid Laser Treatment of Macular Edema Secondary to Branch Retinal Vein Occlusion with Micropulse Infrared (810 Nanometer) Diode Laser

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Macular edema is the most frequent complication of branch retinal vein occlusion (BRVO), occurring in about 60% of cases. The Branch Vein Occlusion Study Group has dem­onstrated that grid laser photocoagulation is effective in reducing visual acuity (VA) loss due to macular edema secondary to BRVO. The Study Group used an argon laser with the ophthalmoscopic end point visible at the time of the laser application.

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Several studies have shown that conventional threshold grid laser treatment for macular edema may be associated with the occurrence of complications including: enlargement of laser scar choroidal neovascularization subretinal fibrosis visual field sensitivity deterioration. More recently, many investigations have shown that the damage due to laser photocoagulation can be decreased by both reducing the duration of laser exposure and using a subvisible clinical end point.

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Purpose: To compare the effectiveness of subthreshold grid laser treatment (SGL T) with an infrared micropulse diode laser with that of threshold grid laser treatment (TGL T) for macular edema secondary to (BRVO)

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Design: Randomized clinical trial. Participants: Thirty-six patients (36 eyes) were randomized either to infrared SGL T (17 eyes) or to krypton TGL T (19 eyes).

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A prospective randomized clinical pilot trial was planned to compare the effects of SGLT performed by infrared micropulse diode laser and of TGLT delivered with krypton laser. Patients affected by BRVO observed in the outpatient department. Inclusion criteria: BRVO occurring 3 to 18 months earlier macular edema involving the fovea sufficient clearing of retinal hemorrhages best-corrected V A (BCV A) of 20/40 or poorer.

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Exclusion criteria: # Detection of retinal capillary nonperfusion # >5 disc diameters on fluorescein angiography # Identification of sensory detachment on optical coherence tomography (OCT), coexistence of any other chorioretinal diseases # Glaucoma # Media opacities # Cataract extraction or lens implantation in the last 12 months # Previous laser treatment.

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Methods: Complete ophthalmic examination visual acuity Early Treatment Diabetic Retinopathy Study chart optical coherence tomography (OCT) fluorescein angiography performed at the time of the study entry and at 6-month intervals, with a planned follow-up of 24 months.

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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 >2 lines of VA gain) at the 12- and 24-month examinations. timing of macular edema resolution.

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Results: Changes in mean FT and TMV from the initial values were statistically significant for TGL T from the 6-month examination (P<0.001) and for SGL T 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 SGL T 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 SGL T group and 11 (58%) of the TGL T group. Moreover, at the 24-month examination 59% and 26% gained 3 lines in the SGL T and TGL T groups, respectively.

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Conclusions: Resolution of macular edema and VA improvement are similar to those obtained with con­ventional TGL T, but SGL T 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 SGL T for macular edema secondary to BRVO.





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