Peripapillary retinal nerve fiber layer thickness changes after panretinal photocoagulation and its relation with visual acuity changes in patients with diabetic retinopathy

Abstract

Background: Panretinal photocoagulation (PRP) is currently the main treatment for proliferative diabetic retinopathy. Optical coherence tomography (OCT) is a noninvasive method of analyzingin vivo retinal architecture. Objectives: The objective was to evaluate the effect of PRP on peripapillary retinal nerve fiber layer thickness (RNFLT) in patients with diabetic retinopathy using OCT and to correlate peripapillary RNFLT changes with the changes in visual acuity (VA). Materials and Methods: This is a prospective study including eighty eyes of eighty patients with proliferative diabetic retinopathy (PDR) and severe non-PDR. PRP was done with frequency-doubled Nd: YAG (532 nm) laser. Peripapillary RNFLT was measured by spectral-domain OCT at baseline and 6 months post-PRP and assessed using paired t-test. The baseline VA and changes in VA 6 months post PRP were recorded. The relationship between RNFL loss and changes in VA was assessed using ANOVA and independent t-test. Results: The mean age of the patients was 60 years, with 65% of males and 35% of females. At 6 months post-PRP, there was a significant reduction in average RNFLT with a reduction in all quadrants, except in the temporal quadrant. According to interval changes of VA, the patients were divided into improved (22.5%), unchanged (48.8%), or worsened (28.7%) groups. Improved VA group showed a significant decrease in peripapillary RNFLT. Conclusion: RNFLT reduction following PRP can be due to axonal loss secondary to the direct or indirect effects of PRP. The extremely mild reduction in the temporal quadrant can be due to the sparing of papillomacular bundle during laser treatment.

Keywords

• diabetic retinopathy
• optical coherence tomography
• panretinal photocoagulation
• peripapillary retinal nerve fiber layer thickness