Topography of Photophobia: Perifoveal Sensitivity Associations in Glaucoma

To determine whether the spatial topography of retinal sensitivity predicts photophobia severity specifically in glaucoma, testing the hypothesis that localized perifoveal function predicts light aversion independently of visual acuity and global disease severity.

Cross-sectional study of 54 eyes (27 participants; mean age, 64.3 ± 9.7 years) exclusively with glaucoma. Psychophysical photophobia thresholds were quantified using a custom LED-based device. Retinal sensitivity was assessed with the Humphrey Field Analyzer 24-2. To isolate spatial patterns from global severity, sensitivities were standardized to within-eye z-scores. Linear mixed-effects (LME) models identified the retinal region most predictive of photophobia.

Photophobia thresholds correlated highly between fellow eyes (R = 0.73, P < 0.001). Model selection across predefined regions indicated that the posterior pole (0°-16°) showed the highest predictive value. In multivariable LME analysis, higher posterior pole sensitivity (z-score) was significantly associated with lower photophobia thresholds (β = -0.078, P = 0.036). Subjective symptom scores (VLSQ-8) showed a marginal association in this restricted cohort (P = 0.080), which was supported by full cohort sensitivity analysis. Conversely, visual acuity (P = 0.456) and lens status (P = 0.101) were not significant predictors. Spatial mapping showed that sensitivity in the perifoveal region (approximately 5°-10°) had the strongest association with photophobia, forming a U-shaped eccentricity profile consistent with the peak somatic density of intrinsically photosensitive retinal ganglion cells (ipRGCs).

Photophobia severity in glaucoma was associated with localized perifoveal sensitivity, independently of visual acuity or lens status. These findings suggest that the perifoveal retinal pathway, potentially involving ipRGC-related signaling, may represent one contributing mechanism underlying light aversion.