Effect of pan retinal photocoagulation on macular ganglion cell - inner plexiform layer and peripapillary retinal nerve fibre layer thickness

: To determine the effect of pan retinal photocoagulation (PRP) on spectral domain optical coherence tomography (SD OCT) morphologic parameters like macular ganglion cell-inner plexiform layer (GCIPL), peripapillary retinal nerve fibre layer (RNFL) thickness and central macular thickness (CMT) in diabetic retinopathy cases. This is a retrospective study including 52 eyes with severe non-proliferative to proliferative diabetic retinopathy without macular oedema who required PRP. Macular GCIPL, CMT and peripapillary RNFL thickness measured at baseline and at 1-, 6-, 12- and 18-months post PRP with SD OCT. CMT, Macular GCIPL and peripapillary RNFL thickness increased significantly at 1 month (p<0.05), thereafter a decreasing trend noted at 6, 12 and 18 months. At 18 month CMT, GCIPL and RNFL thickness are higher than baseline but not statistically significant except temporal RNFL and Average GCIPL (p<0.05). A significant correlation found between changes in temporal RNFL and average GCIPL thickness (Pearson Correlation coefficient r= 0.652, 0.557, 0.782, 0.624 at 1, 6, 12 and 18 months respectively. P<0.05 for all values) CMT, macular GCIPL and peripapillary RNFL thickness increase following PRP; peaking at month 1 and stabilizing through next 18 months. Macular GCIPL thickness could be a reproducible indicator of temporal RNFL.