LONG-TERM TEMPORAL CHANGES OF PERIPAPILLARY RETINAL NERVE FIBER LAYER THICKNESS BEFORE AND AFTER PANRETINAL PHOTOCOAGULATION IN SEVERE DIABETIC RETINOPATHY

Abstract

To analyze the long-term changes of peripapillary retinal nerve fiber layer (RNFL) thickness before and after panretinal photocoagulation (PRP) in patients with severe diabetic retinopathy. In this retrospective observational case series, we reviewed the records of 46 patients (68 eyes) with severe diabetic retinopathy, who were treated with PRP and could be followed for more than 6 months. Peripapillary RNFL thickness and foveal thickness were measured at baseline, 3-month intervals until 1 year post-PRP, and 6- to 12-month intervals after 1 year post-PRP using optical coherence tomography. Long-term changes of peripapillary RNFL thickness and foveal thickness as well as the correlation between the two parameters were analyzed. The average RNFL thickness (360° measurement) decreased significantly from 108.4 μm to 103.5 μm at 2 years post-PRP. The average RNFL thickness increased slightly during the initial 3 months post-PRP and thereafter gradually decreased, showing statistically significant reductions at 2 years post-PRP (false discovery rate adjusted P = 0.0051). The superior and inferior quadrant RNFL thicknesses were significantly decreased at 2 years post-PRP (false discovery rate adjusted P = 0.0119 and 0.0051, respectively). The decrease in the nasal quadrant RNFL thickness showed borderline significance at 2 years post-PRP (false discovery rate adjusted P = 0.0854). However, there was no significant decrease in RNFL thickness for the temporal quadrant at any follow-up time. In addition, there was no significant difference in the foveal thickness. But, the pattern of temporal changes in foveal thickness showed a similar pattern with that of temporal RNFL thickness. This study shows that average RNFL thickness after PRP undergoes early thickening and subsequent progressive thinning throughout the 2 years post-PRP. This temporal change varies according to the peripapillary RNFL quadrant. Our results also indicate that temporal RNFL and foveal thickness have a similar pattern of long-term change after PRP.