Retinal Nerve Fiber Layer Alterations After Photocoagulation: A Prospective Spectral-Domain OCT Study

Purpose: To evaluate the effect of panretinal photocoagulation (PRP) on retinal nerve fiber layer thickness (RNFLT) in treatment-naive patients with proliferative diabetic retinopathy (PDR). Methods: Fifty eight previously untreated eyes of 30 patients with PDR who underwent PRP treatment were enrolled prospectively. All patients had at least six months of follow-up. Detailed ophthalmologic examinations including macular thickness and RNFLT assessments with spectral-domain type optic coherence tomography were performed at baseline as well as the third and sixth posttreatment months. Initial RNFLT and macular thickness of laser administered patients were compared with two separate control groups that were consisted of either nondiabetic patients or diabetics without PDR. Results: The mean age of study patients was 52.4 +/- 7.1 years (Range, 32-66 years) and 16 of them (53.3%) were female. At the sixth post-PRP month, visual stabilization or improvement was achieved in 54 eyes (93.1%). No significant difference was demonstrated in initial RNFLT measurements between the study patients and two control groups (p=0.478). Mean RNFLT was measured as 108.5 +/- 17.5 mu m, 115.8 +/- 17.6 mu m, and 103.0 +/- 16.4 mu m at baseline, third and sixth months of the follow-up, respectively. Although RNFLT increase noted at the third post-laser month was statistically significant compared to its baseline values (p<0.001), there was a significant reduction in RNFLT at the sixth post-laser month compared to its baseline values (p<0.001). Conclusion: RNFLT increase in the third month of follow-up may be related to ensuing axonal edema. Significant RNLFT decrease at the sixth month of follow-up may be attributed to axonal loss secondary to the laser treatment.