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Christopher A. Clark, Ann E. Elsner, Matthew S. Muller, Benno L. Petrig; Peripheral Refraction Across The Posterior Pole Using Structured Illumination. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2717.
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To provide low-cost, nonmydriatic screening for refractive errors and to diagnosis those that may develop myopia. To use a novel retinal imaging system, the laser scanning digital camera (LSDC) and structured illumination, to provide refractive error maps across the visual field.
Twenty subjects with refractive errors ranging from +4.00 to -6.00 and a model eye were studied. An LSDC prototype illuminated the retina with structured illumination (850 nm) to increase contrast in the retinal images, provided by modulating the light source in a striped pattern. For each subject and a model eye, the Michelson contrast was computed across retinal locations from 1 megapixel images acquired while stepping through focus in 0.25 diopter steps. The computed central refractive error was compared with that at peripheral locations from data collected simultaneously in the 36 deg field of view. Bland-Altman and regression analyses were used to compare the subjective refraction with the LSDC auto-refraction, and the refractive errors measured across retinal locations.
Peripheral refraction measures were consistent with results reported in the literature. Specifically, myopes exhibited relative hyperopia in the periphery that was correlated with central refraction (R2=0.42, p = 0.004) across the horizontal meridian, with a slope of -0.042. The vertical meridian showed a tendency towards myopia in the periphery regardless of central refractive error. Three subjects’ data were excluded due to eye movements of several degrees, although the retinal images were clear, indicating additional image alignment and improved fixation targets are needed.
Initial feasibility results have shown the potential for the LSDC to be used as a low-cost device for both retinal imaging and rapid refractive error measurement. The refractive topographical maps provide the potential to screen those at risk of developing myopia or undetected refractive error in underserved populations.
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