Subthreshold grid laser treatment of macular edema secondary to BRVO was compared with continuous wave grid laser to see if the former procedure that is performed with a micropulse diode laser might reduce complications [Ophthalmology. 2006;113(12):2237-2242].
The results from the randomized trial showed macular edema improved rapidly with the conventional laser technique, but overall improvements in visual acuity and macular edema were similar in the two treatment groups. There were no biomicroscopic or angiographic signs of laser treatment in the subthreshold group.
Another study compared subthreshold grid laser with bevacizumab (Avastin, Genentech) in eyes with recurrent macular edema after conventional grid laser treatment [Graefes Arch Clin Exp Ophthalmol. 2015;253(10):1647-1651]. The results, both functional and anatomic, clearly favored anti-VEGF therapy in this setting, Dr. Bandello said.
Targeting the periphery
Laser treatment of peripheral ischemia is based on the idea that it would eliminate VEGF production by nonperfused retina. Various investigators have reported on this approach with conflicting results.
A small study by Rick Spaide, MD, showed panretinal photocoagulation of peripheral areas of retinal vascular nonperfusion in eyes with CRVO had no benefit for improving visual acuity or decreasing anti-VEGF injection burden [Retina. 2013;33(1):56-62].
Similar results were achieved in the RELATE trial, which randomized patients with CRVO or BRVO treated for 24 weeks with anti-VEGF therapy to continue as needed monthly injections alone or combined with scatter and grid laser photocoagulation [Ophthalmology. 2015;122(7):1426-1437]. It found the addition of laser treatment had no long-term functional or anatomic benefits, nor did it reduce anti-VEGF treatment burden, Dr. Bandello said.
In contrast, Tomomatsu et al. reported that retinal photocoagulation of non-perfused peripheral retina in eyes with ischemic BRVO prevented recurrence of macular edema after intravitreal anti-VEGF therapy [Acta Ophthalmol. 2016;94(3):e225-230].
Francesco Bandello, MD