Representing the retinal line spread shape with mathematical functions

Yang, Yi Rong; Wanek, Justin; Shahidi, Mahnaz

doi:10.1631/jzus.b0820184

Cited by 3 publications

(1 citation statement)

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“…Although phase information contained in the PSF was lost by radial averaging, the impact on the PSF was minimized due to the small pupil size. The one-dimensional line profile was normalized to unity and then fit with a Gaussian function, which has been shown previously to provide a good description of the central region of the PSF,22 which is of primary importance in determining visual resolution 23. The standard deviation of the best-fit Gaussian function ( σ opt ) defined optical blur.…”

Section: Methodsmentioning

confidence: 99%

Contributions of Optical and Non-Optical Blur to Variation in Visual Acuity

McAnany

Shahidi

Applegate

et al. 2011

Optometry and Vision Science

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Purpose To determine the relative contributions of optical and non-optical sources of intrinsic blur to variations in visual acuity (VA) among normally sighted subjects. Methods Best-corrected VA of sixteen normally sighted subjects was measured using briefly presented (59 ms) tumbling E optotypes that were either unblurred or blurred through convolution with Gaussian functions of different widths. A standard model of intrinsic blur was used to estimate each subject’s equivalent intrinsic blur (σint) and VA for the unblurred tumbling E (MAR0). For 14 subjects, a radially averaged optical point spread function due to higher-order aberrations was derived by Shack-Hartmann aberrometry and fit with a Gaussian function. The standard deviation of the best-fit Gaussian function defined optical blur (σopt). An index of non-optical blur (η) was defined as: 1-σopt/σint. A control experiment was conducted on 5 subjects to evaluate the effect of stimulus duration on MAR0 and σint. Results Log MAR0 for the briefly presented E was correlated significantly with log σint (r = 0.95, p < 0.01), consistent with previous work. However, log MAR0 was not correlated significantly with log σopt (r = 0.46, p = 0.11). For subjects with log MAR0 equivalent to approximately 20/20 or better, log MAR0 was independent of log η, whereas for subjects with larger log MAR0 values, log MAR0 was proportional to log η. The control experiment showed a statistically significant effect of stimulus duration on log MAR0 (p < 0.01) but a non-significant effect on σint (p = 0.13). Conclusions The relative contributions of optical and non-optical blur to VA varied among the subjects, and were related to the subject’s VA. Evaluating optical and non-optical blur may be useful for predicting changes in VA following procedures that improve the optics of the eye in patients with both optical and non-optical sources of VA loss.

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Section: Methodsmentioning

confidence: 99%