Letter Distortion Mapping in Amblyopia: Spatial Patterns, Stability, and Relationship to Visual Acuity.

Purpose: To investigate whether letter-based perceptual distortions in amblyopia follow spatially consistent patterns across different letters and to determine if these spatial distortion maps are letter specific or reflect a common underlying spatial organization of visual distortion in the amblyopic eye. Methods: Twenty-one individuals with amblyopia completed a distortion mapping task using the letters A, D, and E, shown at 36 visual field locations. Each letter was first viewed with the fellow eye and then with the amblyopic eye. Participants reported distortions, which were recorded to generate binary spatial maps. The task was repeated over three sessions to assess within-subject consistency, and spatial correlations were analyzed across letters and subjects. Results: Letter distortions were reported by 95% of participants and remained consistent across sessions. Within subjects, spatial distortion maps were significantly correlated across letters in 62% of cases (P ≤ 0.028), suggesting shared spatial patterns. However, across subjects, maps were largely uncorrelated, indicating individualized distortion profiles. No single letter consistently showed more distortion across the group, χ2(2) = 1.279, P = 0.5. A strong positive correlation was found between interocular visual acuity difference and overall distortion intensity (r = 0.70, P < 0.001), consistent across all letters. Conclusions: Letter distortions in amblyopia are highly prevalent, reliable, and spatially organized within individuals but idiosyncratic across subjects. These distortions correlate strongly with visual acuity loss, highlighting their potential as a clinically valuable and perceptually relevant measure for characterizing amblyopic visual dysfunction.