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Xin Wei, Pete S Kollbaum, Jun Dong; Theoretical Comparison of Peripheral Defocus between Object Space and Image Space by Optical Modeling. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1812.
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© ARVO (1962-2015); The Authors (2016-present)
As the retina is a tilted image plane in the peripheral visual field to the incident beam, the perceived defocus on the peripheral retina in image space is different from the measured peripheral defocus in object space, where the incident beam is normal to the instrument’s detection plane. This study investigates the theoretical difference between the object-space defocus and image-space defocus in the peripheral visual field.
A wide-angle model eye was constructed to match published measures of peripheral defocus in object space (Atchison et al. 2006). The measured object-space defocus was modeled by minimizing the blur size on the autorefractor’s detection plane through tracing rays from the retina to the object space along the peripheral line of sight. The image-space defocus was estimated by minimizing the blur size on the tilted retina through tracing parallel rays reversely along the same lines of sight. The differences between and object-space defocus and image-space defocus were compared at 0°, 10°, 20°, and 30°for 3.75, 5.0, and 6.5 mm-diameter pupils.
Along the foveal line of sight, the object-space defocus is the same as the image-space defocus. In the periphery, a significant amount of the dioptric difference is observed. In particular, for myopic eyes, the measured object-space defocus underestimates the image-space defocus. For 3.75-mm pupil, the differences are 0.3 D and 0.4 D along 20° and 30° lines of sight. The gap becomes larger as the pupil size increases. Specifically, along the 30° line of sight, the defocus difference increases to 0.6 D for a 6.5-mm pupil.
In the peripheral visual field, the object-space defocus and image-space defocus are different. Unlike foveal vision, to interpret image-space defocus on the peripheral retina from defocus measurements in object space, optical analysis using a wide-angle eye model is required. This step is crucial for designing wide-angle-viewing optics for the eye.
This is a 2021 ARVO Annual Meeting abstract.
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