Ischemia and laser photocoagulation in retinal vein occlusion

Background Retinal vein occlusions (RVO) are associated with retinal ischemia to a highly variable extent. An ischemic retina may lead to the development of neovascularization and further to secondary complications such as neovascular glaucoma, vitreous hemorrhage or tractional retinal detachment. Numerous factors such as vascular endothelial growth factor (VEGF) and other cytokines are produced in the ischemic area, which cause macular edema. Before the introduction of intravitreal drug injections (IVI), retinal laser photocoagulation was the leading form of treatment. Macular laser photocoagulation was applied in the form of focal laser or grid laser in patients with branch retinal vein occlusion (BRVO) to treat macular edema. In patients with ischemic RVO, panretinal laser photocoagulation (PRP) was recommended for treatment of secondary neovascular complications. The value of laser treatment in the management of patients with RVO changed after the introduction of IVI treatment. Aim This article presents a review of the current study results and the recommendations for performing laser photocoagulation of the central and peripheral retina in patients with RVO. Conclusion Conventional focal or grid laser photocoagulation has been replaced by IVI treatment in the management of macular edema secondary to BRVO; however, macular laser treatment can still be considered in patients with BRVO if the macular edema persists despite the use of available IVI drugs. The use of central laser photocoagulation in these cases is based on the findings of fluorescein angiography. Disseminated panretinal laser photocoagulation is still indicated in RVO patients who have large areas of nonperfusion, have developed neovascularization and/or late complications. Targeted laser photocoagulation of the peripheral areas of nonperfusion has recently been recommended by several authors and is expected to improve not only the visual outcome of IVI treatment, but more importantly to also reduce the duration of treatment and the number of re-injections needed. Clear evidence for targeted laser treatment is not yet available and is a focus of currently ongoing prospective randomized studies.