Correlation of retinal nerve fiber layer thickness with optic disc parameters and disc damage likelihood scale in primary open-angle glaucoma: a cross-sectional study
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Abstract
Objective: To evaluate the relationship between retinal nerve fiber layer (RNFL) thickness and various optic disc parameters and Disc Damage Likelihood Scale (DDLS) in patients with primary open-angle glaucoma (POAG).
Methods: This cross-sectional study, conducted at Lahore General Hospital, included 295 eyes of 148 diagnosed/suspected POAG patients, aging >18 years. Patients with significant refractive errors, media opacities, history of trauma, and poor OCT signal strength were excluded. Comprehensive ocular examination was performed, and optic disc measurements were recorded. RNFL thickness was assessed using optical coherence tomography (OCT). Disease severity was staged DDLS. Statistical analysis involved descriptive statistics, Kolmogorov-Smirnov test for normality, and Spearman correlation coefficients.
Results: Of the 148 patients (90 males, 58 females; mean age 52.41±15 years), mean RNFL thickness was 82.21±14.75 µm. Mean RNFL thickness was 82.3±14.8 µm. The mean average CDR was 0.67±0.12 and mean vertical CDR was 0.64±0.12. The mean rim-to-disc ratio was 0.17±0.13. The median DDLS stage was 4 (IQR 3–5). Correlation analysis revealed a moderate negative correlation between RNFL thickness and vertical cup-to-disc (CD) ratio (r= -0.45), a strong positive correlation between RNFL thickness and rim-to-disc ratio (r=0.70), and a strong negative correlation with DDLS (r= -0.65). DDLS showed a moderate positive correlation with vertical CD ratio (r=0.55) and a very strong negative correlation with rim-to-disc ratio (r= -0.80).
Conclusions: DDLS and rim to disc ratio are more reliable methods for assessing glaucomatous damage than the vertical or average CD ratios. Therefore, DDLS and rim-to-disc ratios should be integral parts of glaucoma assessment.
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