Comparison of the Effects of the Pattern Scan and Conventional Single Spot Panretinal Photocoagulation in Patients with Proliferative Diabetic Retinopathy; A Randomized Clinical Trial

The retinal laser photocoagulation is the gold standard treatment of the proliferative diabetic retinopathy. Nowadays, we can perform panretinal photocoagulation with single spot or pattern scan laser methods. This study aimed to compare the retinal ischemic changes and the retinal neovascularization regression between these two techniques. In a prospective clinical trial study, 146 eyes of 73 patients with proliferative diabetic retinopathy was enrolled. One eye of patients was treated with single spot laser photocoagulation randomly and other eye was preserved for pattern scan laser photocoagulation. The changes of retinal ischemia on the basis of noncapillary perfusion and the regression of neovascularization on the basis of amount of leakage on fluorescein angiography were compared between the two groups after 6 months. There was no significant difference in the retinal neovascularization regression of disc and elsewhere in eyes treated with pattern scan (P = 0.26) or single spot laser (P = 0.31). While the areas of the retinal ischemia progression was significantly higher (9 cases) in group treated with pattern scan in comparison to other group (2 cases) (P = 0.02). The areas of retinal ischemia progression were higher after treatment with pattern scan laser compared to single spot laser. Future researches are recommended to find a better modality than the pattern scan to induce regression of the retinal ischemia similar to the single spot laser technique.