Abstract
PURPOSE: To quantify visual photosensitivity discomfort thresholds (VPDT) in individuals with chronic ocular pain (COP) compared to controls without COP and explore relationships between VPDT, demographics, clinical factors, and ocular metrics. METHODS: Prospective case-control study of 75 participants: 36 with COP (age 46.5 ± 15.6 years; 56 % female) and 39 controls (39.2 ± 15.6 years; 56 % female). COP was defined by self-reported ocular pain intensity ≥15 on a numerical rating scale (range, 0-100) for ≥3 months. COP cases were subclassified into inflammatory (Sjögren's disease) and neuropathic ocular pain subgroups. VPDT was measured using the Ocular Photosensitivity Analyzer (OPA), and ocular symptoms were assessed using the Visual Light Sensitivity Questionnaire (VLSQ-8; 8-40) and Ocular Surface Disease Index (OSDI; 0-100), with OSDI Question 1 addressing light sensitivity (OSDI-Q1; 0-4). RESULTS: COP patients exhibited lower VPDT than controls (log lux, 1.60 ± 1.17 vs. 2.42 ± 1.05; P = 0.006), indicating greater photosensitivity discomfort. No differences in VPDT were seen across COP subtypes. COP patients also reported greater symptom severity than controls, with higher VLSQ-8 (21.92 ± 1.41 vs. 9.03 ± 0.53), OSDI (50.84 ± 3.88 vs. 2.82 ± 0.85), and OSDI-Q1 (2.00 ± 0.24 vs. 0.14 ± 0.06) scores (all P < 0.001). VPDT negatively correlated with VLSQ-8 (ρ = -0.75) and OSDI-Q1 (ρ = -0.62), demonstrating alignment between subjective light sensitivity symptoms and OPA-measured photosensitivity discomfort. Multivariable regression identified fibromyalgia as the strongest predictor of VPDT (19.6 % variance explained), with chronic fatigue improving the model (26.5 %). CONCLUSION: COP subjects display greater photosensitivity-related discomfort than controls, highlighting the OPA's potential as a psychophysical tool for quantifying photoallodynia. Further research is needed to assess its diagnostic utility across COP subtypes.