Study of retinal nerve fiber layer thickness in diabetic patients using optical coherence tomography

PURPOSE: This study aimed to assess and compare the changes in peripapillary retinal nerve fiber layer (RNFL) thickness in nondiabetics and diabetics with various stages of diabetic retinopathy (DR). METHODS: The study subjects were divided into four groups based on their diabetic status and findings, namely, controls (normal subjects without diabetes [NDM]), diabetics without retinopathy (NDR), nonproliferative DR (NPDR), and proliferative DR (PDR). Peripapillary RNFL thickness was assessed using optical coherence tomography. One-way analysis of variance (ANOVA) with the post-Tukey HSD test was done to compare RNFL thickness in different groups. The Pearson coefficient was used to determine the correlation. RESULTS: There was statistically significant difference in measured average RNFL (F = 14.8000, P < 0.05), superior RNFL (F = 11.7768, P < 0.05), inferior RNFL (F = 12.9639, P < 0.05), nasal RNFL (F = 12.2134, P < 0.05), and temporal RNFL (F = 4.2668, P < 0.05) across the different study groups. Pairwise comparison showed that there was a statistically significant difference in RNFL measured (average and all quadrants) in patients with DR (NPDR and PDR) and the NDM control group (P < 0.05). In diabetics without retinopathy, the RNFL measured was reduced compared to controls, but it was statistically significant only in the superior quadrant (P < 0.05). Average RNFL and RNFL in all quadrants showed a small negative correlation with the severity of DR and it was statistically significant (P < 0.001). CONCLUSION: In our study, peripapillary RNFL thickness was reduced in diabetic retinopathy compared to normal controls and the thinning increased with the severity of DR. This was evident in the superior quadrant even before the fundus signs of DR set in.