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M.D. Crossland, L.E. Culham, G.S. Rubin; What Limits Reading Performance in Patients with Newly Developed Macular Disease? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):165.
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Purpose: Difficulty with reading is a frequent complaint of patients with central scotomas due to macular disease (MD). Even with optimal magnification, reading speed is reduced in MD patients so reading difficulty is not purely attributable to the loss in visual acuity. The purpose of this study was to identify which aspects of visual behaviour contribute to impairment of reading speed. Methods: 20 patients with "new" MD (scotoma development in the better eye within the previous month) (VA range 0.12 to 0.92 logMAR) were recruited along with 3 age-matched subjects without MD. Reading speed was assessed for sentences at 3x threshold acuity and for passages of N20 size text . Eye movements were recorded using a gazetracker (Eyelink, SensoMotoric Instruments, Germany). Fixation characteristics and scotoma size were measured using a Scanning Laser Ophthalmoscope (SLO-101, Rodenstock, Germany). Results: Control subjects' suprathreshold reading speed ranged from 162 to 189 wpm (mean 175 wpm, sd 14). Patients' suprathreshold reading speed ranged from 20 to 118 words per minute (mean 76 wpm, sd 33). Visual acuity accounted for only 17% of the variance in patients' reading speed. Stepwise multiple regression indicates that saccadic properties (in particular the number of saccades to the start of a line), scotoma size and contrast sensitivity can more accurately predict reading speed. These factors account for 91% of the variance in reading speed for the suprathreshold sentences. Similar results were found for the N20 size text, with these factors accounting for 62% of the variance in reading speed. Conclusion: Reading speed is significantly reduced in patients with new macular disease. This reduction is due to a variety of factors of which eye movement control is the most important. This knowledge will be of benefit to practitioners working in the rehabilitation of patients with macular disease.
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