Abstract
Abstract: :
Purpose:The process of reading is complex with central and peripheral word recognition thresholds displaying unique characteristics when compared to single letter recognition. Central vision loss is a major concern in Western society due to the high prevalence of age–related macular degeneration (AMD). We studied letter and word recognition thresholds for different contrast levels and different eccentricities, in order to determine the effect of word orientation and eccentricity. Methods: Letters or 4–letter words of different orientations were presented for 100msecs on a computer monitor, both at the fovea and at 10 degrees eccentricity. The letters and words were presented at horizontal (H); up (U); down (D); and vertical (V) orientations. Recognition thresholds were determined for all presentation conditions at 5% and 90% contrast levels. For each experimental series, data was collected from 6 subjects, over five consecutive days to examine any learning effects. Results: For foveal presentations, words of orientations other than horizontal showed an improvement over the five sessions, but only when the contrast was high. However, for words presented at 10 degrees, word recognition thresholds were significantly improved over the five sessions (ANOVA, p<0.05) for all orientations and contrasts (over 0.3 log units). Letter recognition thresholds showed no significant improvement with training for any condition, centrally or peripherally. Conclusions: In the fovea, only high contrast word recognition of U or D orientations showed a significant improvement. However training improved word recognition thresholds in peripheral vision, irrespective of contrast or orientation. These results have implications for patients with AMD, as peripheral word recognition will improve with training.
Keywords: reading • learning • low vision