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Biomedical subjects

A Remole

Publications and source records attributed to A Remole.

51 records · Page 3Linked to original sources
PubMed1979

Contrast thresholds vs border enhancement: sensitivity to retinal defocus.

The two visual responses, contrast threshold and border enhancement, are both affected by retinal image quality. Thus, with increasing defocus of the retinal image contrast thresholds with sinusoidal line gratings increase, and the enhanced region near a border becomes wider. These two visual responses were compared to determine their suitability as gauges of retinal image quality. Border enhancement was found to be more sensitive to deterioration of the retinal image in the form of defocus than contrast thresholds throughout the greater portion of the grating frequency spectrum. However, the contrast threshold increases in sensitivity toward cutoff frequency, and beyond a certain high frequency it surpasses border enhancement in that respect. At the same time, for these optimum frequencies, the contrast range is exhausted within a relatively small defocus range. Therefore, a limitation is imposed on the usefulness of the contrast threshold as an index of retinal image quality.

Humans↗
PubMed1978

A subjective method of monitoring corneal scattering.

Border-enhancement spread is a new criterion for assessing the quality of the retinal image. In one study, it was found that the width of the enhanced region increases with the steepness of a contact lens fit, and this increase was attributed to scattering accompanying corneal edema arising from tight-fitting lenses. The present study tested this hypothesis. Corneal thickness and border-enhancement spread were measured concurrently at regular intervals during and after contact lens wear. It was found that border-enhancement spread generally follows changes in corneal thickness. Since scattering increases with corneal swelling, the findings generally support the hypothesis. However, it was also found that variables not originating in the cornea sometimes modify the retinal-image quality and thus mask the scattering effects. Future applications of the methods are discussed.

Contact Lenses↗
PubMed1977

Border enhancement as an index of contact lens performance.

In simultaneous border contrast enhancement, a border formed by an abrupt luminance discontinuity is perceptually enhanced on the bright side by a band of greater brightness and on the dark side by a band of greater darkness. The width of these perceived bands is very sensitive to small changes in the retinal image quality. This study explored the effect of contact lenses of varying steepness on the border enhancement spread. It was found that, over time, the effect of a contact lens on this spread generates a characteristic function. Furthermore, certain features of this function reflect the degree of steepness of the contact lens. It is suggested that the most important factors determining this function are tear flow and scatter-producing corneal edema.

Contact Lenses↗
PubMed1977

Effect of scattered light on extent of border enhancement.

A contrast border, formed where 2 uniform fields of differing luminance meet, was viewed through filters containing a scattering agent. The filters resembled the cornea and crystalline lens in that the amount of light scattered increased exponentially toward the direction of the indicent light. The perceptually enhanced regions on both sides of the border were measured for various concentrations of the scattering agent. Measurements were obtained for several luminances of the brighter field, the darker field remaining constant. It was found that the width of the enhanced region, both on the bright and on the dark side of the border, increased approximately linearly with the logarithm of the amount of light scattered. The increase was of approximately the same order for all of the luminances tested.

Humans↗