Effects of panretinal photocoagulation on macular structure and function in patients with proliferative diabetic retinopathy

Abstract

Purpose : The direct effects of panretinal photocoagulation (PRP) on retinal structural and functional changes are incompletely understood. We performed a prospective cohort study to test the hypothesis that patients with PDR manifest changes in retinal structure and function within one year following PRP.

Methods : 15 healthy, age-matched controls and 15 adults with untreated PDR underwent contrast sensitivity, frequency doubling perimetry, photostress recovery, dark adaptation, and Humphrey visual fields to assess retinal function. Retinal structure was also examined with spectral domain optical coherence tomography (SD OCT) and semiautomatic retinal layer segmentation to assess changes in retinal layer thickness. All tests were done within one month before PRP and at, on average, 9 months after PRP. Wilcoxon signed-rank test was used to compare visual function testing and SD OCT findings from patients before and after PRP. The critical significance level was adjusted to P < 0.0007 after correcting for multiple testing according to the Bonferroni correction.

Results : Performance on all five visual function tests was significantly reduced in patients with PDR prior to PRP compared with healthy adult controls. There were no significant changes in mean group performance on any visual function tests in PDR patients following PRP. However, approximately half of PDR patients experienced a clinically significant reduction in Humphrey peripheral visual fields, dark adaptation time, and prolonged photostress recovery time after PRP. Segmental analysis of SD OCT findings by ETDRS region revealed a 3 - 4 μm increase in thickness of the inner superior (P = 0.0006) and inner nasal (P = 0.0001) quadrants of the inner nuclear layer in PDR patients following PRP. All other SD OCT findings were not statistically significantly different in PDR patients between their pre-PRP and post-PRP visits.

Conclusions : These findings suggest that PDR impairs retinal function, and PRP modestly worsens macular photoreceptor/RPE function and peripheral fields with minimal impact on macular structure 9 months after PRP. These data help to understand the mechanisms of visual impairment in persons with diabetes.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.