A Comparative Study of the Effect of Different Laser Techniques on the Choroidal Thickness

Abstract

Diabetes mellitus is an important metabolic disease that is often associated with injury to several ocular structures. Diabetic retinopathy is one of its most common chronic microvascular complications. Recent evidence indicates that diabetic retinopathy is a neurovascular disease of the retina. Increased vaso-permeability occurs as a result of breakdown of the blood retinal barrier due to many factors: altered glial cells, loss of pericytes, endothelial cell death, leukostasis in the retinal vasculature, poor function of the tight junctions in the retinal vasculature, upregulation & expression of vascular endothelial growth factor and protein kinase c, and altered vitreo-retinal interface with a thickened taut posterior hyaloid with persistent vitreo-macular traction. Spectral domain optical coherence tomography can successfully examine and measure choroidal thickness in normal and pathologic states. Panretinal photocoagulation is effective in treatment of proliferative diabetic retinopathy because it reduces vascular endothelial growth factor. However, panretinal photocoagulation can cause permanent peripheral visual field loss and decreased night vision and may exacerbate diabetic macular edema, which makes alternative treatments desirable. The aim of this study is to compare and evaluate choroidal thickness before and after panretinal photocoagulation, modified grid photocoagulation and combined (panretinal photocoagulation & modified grid photocoagulation) using spectral-domain optical coherence tomography. This study included 30 eyes of 30 patients with diabetic retinopathy (9 males, 21 females). Their ages ranged from 42 to 60 years with mean age was 50.83 ± 5.34 years (SD). Patients were divided into 3 equal groups Group A: Patients with proliferative diabetic retinopathy; underwent panretinal photocoagulation, Group B: Patients with macular edema; underwent modified grid photocoagulation, Group C: Patients with proliferative diabetic retinopathy & macular edema; underwent combined (panretinal photocoagulation & modified grid laser). In all the 3 groups, the choroidal thickness was decreased after 3 months. Although, panretinal photocoagulation group showed slight increase above baseline after 1 month. Among the 3 groups only the modified grid laser photocoagulation group showed statistically significant increase between pre & post best corrected visual acuity while we did not find statistically significant difference with the other 2 groups.