Visual Field Indices or Retinal Nerve Fiber Layer? Predictors of Relative Afferent Pupillary Defect Severity in Asymmetric Glaucoma

Abstract

Objective: To determine the association of visual field indices like mean deviation (MD) and visual field index (VFI) and retinal nerve fiber layer (RNFL) thickness with relative afferent pupillary defect (RAPD) in asymmetric glaucoma and to quantify the amount of inter-eye differences in these parameters required to predict severity of RAPD grades.

Methodology: This study was conducted at glaucoma clinic of ophthalmology department of Hayatabad Medical Complex, Peshawar, Pakistan from July 2024 to March 2025. Patients diagnosed with asymmetric glaucoma (all types) and clinically detectable RAPD were included in this study. RAPD was recorded using clinical plus grading. The RNFL thickness, mean deviation (MD), visual field index (VFI), and their inter-eye differences were calculated. Ordinal logistic regression assessed the relationship between RAPD grades and the inter-eye differences in these parameters. A p-value<0.05 was set for statistical significance.

Results: In 126 participants recruited, the mean age was 52.48 ± 14.63 years and 97 (77%) were males. The inter-eye differences in OCT-RNFL (global or sectoral), MD and VFI were statistically significant (p<0.001). Inter-eye difference in MD was the only significant predictor of RAPD grade (OR=1.225, 95% CI=1.009-1.489, p=0.04), suggesting that greater differences in MD are associated with higher RAPD severity. The association between the glaucoma stage of the worse eye and RAPD grades were found statistically insignificant (p=0.345).

Conclusions: Inter-eye differences in RNFL thickness, MD, and VFI were significantly associated with RAPD severity. Visual field asymmetry (MD difference) emerged as the strongest predictor of RAPD grade, while glaucoma stage showed no association with RAPD severity.