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G. S. Rubin, M. Feely, G. A. Hahn, A. Messias, S. Trauzettel-Klosinski; Saccadic Eye Movements and Reading in Patients With Advanced AMD - The AMD Read Project. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5527.
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We have recently shown that reading performance in patients with newly acquired age-related macular degeneration (AMD) is predicted by fixation stability (1) and perceptual span as assessed by saccadic eye movements (2). The purpose of this study is to investigate whether the same eye movement factors account for reading performance in a heterogeneous sample of patients with established AMD who were tested at two European eye clinics.
Patients with advanced AMD were recruited from Moorfields Eye Hospital, London (MEH) and University Eye Hospital, Tubingen (UEH). To qualify for the study, patients had to have vision worse than 0.5 logMAR (6/18) and a macular scotoma in the better-seeing eye. Patients underwent an extensive vision test battery including high and low contrast acuity, scanning laser ophthalmoscopy, eye movement analysis using a video eye tracker (SMI EyeLink I), and a reading assessment using standardized texts that were translated into four European languages and viewed with the patient's customary magnifier. Fixation stability was quantified using the sum of local bivariate contour ellipse areas (LBCEA) and reading eye movements were evaluated for the number of forward and regressive saccades and the number of saccades to return from the end of one line to the beginning of the next line.
Sixty patients were tested, 40 from MEH and 20 from UEH. The MEH patients had slightly worse acuity on average (10% contrast: 1.02 ± 0.29 vs 0.92 ± 0.27; high contrast: 0.82 ± 0.26 vs 0.70 ± 0.20 logMAR), but the difference was not statistically significant (p > 0.1). High- and low-contrast acuities were significantly correlated with reading speed but accounted for less than 15% of the variance. Fixation stability accounted for 34% of the variance in reading speed for the MEH patients (data not available for UEH). The best predictor of reading speed was the average length of forward saccades, which is an indirect measure of perceptual span and accounted for 55% of the variance.
These results confirm earlier findings that fixation stability and perceptual span are important predictors of reading speed in patients with central scotoma due to AMD, and demonstrate that a standardized reading and eye movement assessment can be applied across diverse clinical populations with similar results.1. M. D. Crossland, L. E. Culham, G. S. Rubin, Ophthalmic Physiol Opt 24, 327 (2004).2. M. D. Crossland, G. S. Rubin, Vision Res 46, 590 (2006).
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