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M. F. Marmor, D. J. Marmor; How We See: New Simulations of Vision (With and Without Macular Disease). Invest. Ophthalmol. Vis. Sci. 2009;50(13):5341.
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Vision is classically simulated by a clear photograph, with a grey spot in the center when there is macular disease. But at any moment in time, we see clearly only in the central few degrees, and cannot recognize more peripheral objects without moving our gaze. We have sought to create images that would demonstrate better the visual challenge of reading or looking at a scene for normal subjects and patients with macular disease.
Data from studies on eccentric visual acuity have been reviewed to estimate plausible values for acuity fall-off in normal untrained subjects. Computer simulations of blur, and of scotomas, have been generated with careful attention to visual angle, viewing distance, etc. and with care to mimic the sensations described by patients with macular disease.
Our simulated images of reading material, and of scenes at different distances, show the extent to which sharp acuity is limited to the center of gaze (and attention). For normal individuals this is important for understanding why and how we scan in reading, but also how we may miss important elements of the environment in tasks such as driving. The simulations show dramatically how scotomas of different size limit the ability of a patient to read or negotiate in different environments.
Computer simulations which show a fall-off of visual acuity with eccentricity illustrate more accurately than conventional photographs the limitations of vision (or macular disease) at any moment in time. These images should prove valuable for teaching how we see, and for educating patients and families about the effects of macular disease.
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