摘要:

A visual evoked potential (VEP) component that appears in the power spectrum only during binocular fusion has recently been discovered. When both eyes are stimulated with the same checkerboard but at different pattern reversal rates, this fusional component appears at a frequency intermediate between the two stimulus frequencies. We have proposed a model to explain the appearance of this intermediate component and have tested the model's predictions that the fusional component will remain constant independent of binocular or monocular changes in stimulul contrast As predicted by the model, changes in contrast over the range of 10 to 90% produced no significant change in the power of the fusional component.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The optical performance of standard plastic and glass spectacle lenses was compared at increasing angles of oblique gaze up to 40° on either side of the optic axis of the lenses. For this purpose, the border enhancement method was used, a method which is suitable for monitoring small order changes in the retinal image. It was found that the enhancement band width increases with obliquity of gaze in all cases, signifying a deterioration in the retinal image. A glass lens will exaggerate this deterioration to some extent, whereas a plastic lens will exaggerate it to the greatest extent. It is shown that the relatively poorer performance of plastic is due to a relatively larger amount of narrow-angle scattering than is produced by glass.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

A mechanism for the rupture of the tear film is identified. The key step in the process of tear film breakup is the instability and eventual rupture of the mucous layer of 0.02 to 0.04 μm thickness, which covers the epithelium. The rupture is caused by the van der Waals dispersion forces acting on the mucous layer. The aqueous part of the tear film then ruptures because it comes into contact with the exposed hydrophobic epithelium. The time of rupture derived from the proposed mechanism is consistent with the range of observed breakup times (BUT's) and other clinically observed characteristics of rupture. The proposed mechanism has implications in understanding the cause of adhesion of the contact lens to cornea and in the rapid buildup of deposits on the lens surface, both of which are attributed to the mucous deficiency. It also suggests various possibilities for diagnosis and treatment of pathological conditions of a dry eye, and lends support to existing ones.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The method proposed by Farnsworth for scoring the 100-Hue test is reviewed, and measures of the orientation and strength of the error axis are proposed. The error axis and its magnitude are determined by the phase and amplitude, respectively, of the best-fit sinusoid to the function that results from Kitahara's transformation of the subject's arrangement of the colors. In addition, a computer program, written in BASIC, that scores the 100-Hue test according to those methods is described, and a listing of that program is provided in the Appendix.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Modifications of the Farnsworth-Munsell 100-Huetest (e.g., selection of new fixed-reference caps from within the test) have been proposed, with little or no theoretical justification or experimental verification. Predictions based on theoretical considerations of the underlying nature of the test and verified by experimental measurements on subjects with known color defects demonstrate that (1) modification can destroy the very nature of the test; (2) modification can alter axis determination and there-tore, potentially, the diagnosis; (3) the resulting test scores cannot be compared reliably to established norms; and (4) accurate predictions of test performance can be made from theoretical considerations.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The clinical effect of detecting visual field loss was studied in 66 patients with visual field defects. Fifty-two percent of defects were the result of conditions which were themselves considered to be significant. Visual field results were considered to have made vital and important contributions to that diagnosis in 28% and 23% of cases, respectively. The results also brought about a change in the intended management strategy in 39% of cases, but were also helpful in another 35% of cases. It was concluded that the clinical importance of regular perimetric examination is emphasized by these results, which may in turn contribute to the detection of unexpected visual field defects.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Eighty-nine optometry students were divided into an asymptomatic group and a symptomatic group on the basis of a case history. A forced vergence fixation disparity (FD) curve was generated for each subject using a Disparometer (Vision Analysis, Columbus, Ohio). Slopes were calculated for each curve. In addition, each curve was labeled steep or flat based on a previously determined cutoff point of −0.96 min/Δ (Sheedy, 1980). Steep curves did not correlate well with symptomatic patients, whereas flat curves did not correlate well with asymptomatic patients. An independent t-test found no significant difference between the two groups.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Antimetropia is a condition in which one eye is myopic and the fellow eye is hyperopic. This report describes functional and optical characteristics of a patient with a substantial degree of antimetropia.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID