ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The profession of optometry has been very successful in providing optical corrections for spherocylindrical refractive errors. In this paper, I examine one attempt to improve retinal image quality beyond that afforded by a standard refractive correction. Ocular chromatic aberration is one of the factors that prevent retinal image quality from reaching the upper limit set by the wave nature of light. It can be subdivided into three primary aberrations (wavelength-dependent differences in image plane, image position, and image size). We have been able to measure all three of these using psychophysical techniques. Although attempts to provide an optical correction for wavelength-dependent refractive errors have been optically successful, they have failed to improve vision. Several possible explanations are given for this failure.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Pattern-evoked cortical potentials (PECPs) were recorded in response to the onset of blue and black, square wave gratings superimposed on a bright orange background. Several lines of evidence, including spectral sensitivity and the absence of response in a tritanopic subject, indicate that the measured cortical potentials reflect input from S cones. Spatial and temporal tuning of this response are comparable to psychophysical measures of the S-pathway. In agreement with previous studies of achromatic and chromatic spatial processing, a comparison of the response to patterns of different complexity indicates that spatial processing in the S-pathway can be described by linear systems analysis. An oblique effect for the S-pathway is demonstrated. Additional findings which bear on the nature of postreceptoral processing in the S-pathway are considered. Included are measurements from a patient with diabetic retinopathy. This study underscores the potential importance of the S-pathway for spatial information processing.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Two methods used for evaluation of glare in patients with opacities of the ocular media are compared. One is a low contrast letter test and the other is a direct light scattering meter. Theoretical expressions for the measures obtained from the two different glare tests are derived in terms of the point spread function. Measurements on healthy test persons wearing diffusive glasses with known light scattering properties were in good agreement with the theory. Data from 26 cataractous eyes are presented and discussed in light of the theory.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Measurement of the monocular components of fixation disparity indicated a higher prevalence of asymmetric contributions to the total deviation than previously reported. Furthermore, the exact proportion varied from moment to moment. Two of six subjects showed significant changes in fixation disparity over a period of 1 week. For all six subjects the changes in fixation deviation of one eye were virtually independent of those changes occurring in the other eye. In other words, these monocular variances were uncorrelated. Settings of the monocular components of binocular fixation disparity were accomplished at an accuracy close to that achieved by using a monocular vernier technique. The remaining differences appeared to be due to occasional instabilities during binocular viewing. The usual method of clinical measurement in which only one element is moved is not always equivalent to that determined by summing the two monocular components. The principal process measured by subjective fixation disparity appears to be either oculomotor or localized directional shifts of a monocular nature.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Previous experiments that have compared monocular vernier acuity in amblyopic, monocularly blind, and normal binocular subjects have been confined to the center of the retina. Based on brain changes that accompany the early disruption of form vision in one eye, monocularly blind subjects (that is, those who have completely lost the ability to process form vision in one eye) and amblyopic subjects are expected to have better vernier acuity in their normally functioning eye than subjects with normal binocular vision. Results from such studies have been ambiguous. This experiment was set up to study monocular vernier acuity in the central and peripheral retina of the three groups of subjects mentioned above. The results show that, at the center, monocularly blind subjects have the best vernier acuity followed by the amblyopic subjects and, finally, the normal binocular subjects have the worst acuity. In the peripheral retina, no significant differences were found between the three groups. A possible explanation has been provided for this finding.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

A study was conducted with the purpose of examining the possible effects of vertical and horizontal eye movements upon accommodation. A special Badal stimulator was made which was vertically rotatable around the center of an eye. The stimulator was attached to the Three-Dimensional Optometer III (TDOIII), which could measure accommodation, eye movement, and pupil diameter simultaneously. The reliability of the TDOIII measurements of accommodation was checked by comparing with a stigmatoscope measurement. Three young males served as subjects. A small but definite near accommodation was measured dynamically in association with vertical eye movement. We believe this to be the first report of this finding. The amount of near accommodation with downgaze showed a tendency to decrease when the target was brought near.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Ocular protrusion data were obtained on 309 black adults using a Hertel exophthalmometer. The mean protrusion value for black men and women was 18.20 and 17.46 mm, respectively. The upper limit of normal was 24.14 and 22.74 mm for males and females, respectively. The differences between base measurement and mean protrusion values of black men and women were significantly different (p<0.015). These data are compared with those of adult white subjects and show that blacks have a higher range of normal than whites. The data indicate that the published upper limit of normal (21 mm) for exophthalmos is not appropriate for adult black patients.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Ocular ptosis secondary to the wearing of rigid contact lenses has been reported. Generally this ptosis is not of the classical variety, and appears to be an edematous or inflammatory response of the lid to the presence of the lens. We report a case of acute ptosis secondary to rigid lens wear in a patient who had undergone cataract surgery. The patient had been a contact lens wearer before surgery, and developed the relative ptosis postsurgically in the nonoperated eye. The ptosis resolved without any form of intervention other than ceasing to wear the contact lens. We feel that in cases where rigid lens wear is discontinued unilaterally for any reason, and a relative ptosis is noted, it should be given time to resolve before any therapeutic regimen is considered.

ISSN:1040-5488    

出版商:OVID    

年代:1992

数据来源: OVID