摘要:

Soft contact lenses worn by six patients (12 eyes) diagnosed as having contact lens-induced superior limbic keratoconjunctivitis (SLK) and from four patients (5 eyes) with giant papillary conjunctivitis (GPC) were analyzed for protein concentration and for elemental content. Fifty-five percent water content, ionic lenses containing methacrylic acid had high protein concentration. Calcium was not a common element found on protein-coated lenses. Sulfur and iron were found on used and new lenses. An elevated level of mercury was detected in one gray lens that had been disinfected in thimerosal-preserved saline with a high heat disinfection unit by a patient with SLK.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Ophthalmic lenses made from glass, hard resin, and polycarbonate are inspected with a shadowgraph to determine the nature, frequency, and severity of localized defects, including power aberrations. The most common localized defects are scratches and pits left by incomplete polishing and localized power aberrations caused by variations in the thickness of scratchresistant coatings. Localized defects are more likely in polycarbonate lenses than in glass or hard resin lenses. The compliance of lenses with standards that limit localized defects is discussed.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Simple methods were developed to estimate refractive errors when intraocular lenses are not fitted optimally within pseudophakic eyes. The accuracy of these methods was determined by comparing results obtained with them to results obtained by raytracing through a model eye. Accuracy was good for longitudinal displacement and tilting, and reasonable for transverse displacement. Refractive errors are related linearly to the magnitude of the longitudinal displacement, and are related to the square of the magnitude of tilt or transverse displacement. The refractive error upon transverse displacement is quadratically dependent upon lens shape.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Three chromatic reference stimuli (red, green, and blue) seen under five adaptation conditions (red, green, blue, achromatic, and darkness) were appearancematched to subsequent color stimuli seen under achromatic conditions. The experimental results have been used to verify the opponent-color color-vision model and also to check the validity of some of the published transformation equations for predicting the tristimulus values of colors matched to a reference stimulus seen under different chromatic-adaptation conditions. It is concluded that the extant transformation laws are not sufficiently general to be applied to all adaptation conditions.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

It has been shown previously that induced aniseikonia amplifies any latent fixation eccentricity associated with binocular fusion stress. This study determines if the retinal location of the stimulus plays a part in this effect. The stimulus consisted of a vertical border formed by the juxtaposition of two fields of unequal luminances and a line segment parallel to the border whose distance from the border can be varied. At the same time, the border allowed the application of a previously tested method of measuring fixation eccentricity, based on the border-enhancement response. It was found that the fixation eccentricity produced by aniseikonia is maximal for the smallest distance of the variable target from the border but unaffected by the larger distances tested. It was concluded that the retinal location of the stimulus has an important influence on the response to aniseikonia.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Measurement of refraction in the principal meridians and off-axis meridians in both directions from the visual axis was undertaken. The extent of disagreement between the sine-squared law and the actual astigmatism of living astigmatic eyes was calculated. The corrected visual acuity correlates with the residual ametropia. The conoid of Sturm is not the same for each eye.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The exact equation for sagitta of spherical surfaces is generalized to toric surfaces which include spherical and cylindrical surfaces as special cases. Lens thickness, therefore, can be calculated accurately anywhere on a lens even in cases of extreme spherical and cylindrical powers and large diameters. The sagittae of tire- and barrel-form toric surfaces differ off the principal meridians, as is shown by a numerical example. The same holds for pulley- and capstan-form toric surfaces. A general expression is given for thickness at an arbitrary point on a toric lens. Approximate expressions are derived and re-expressed in terms of matrices. The matrix provides an elegant means of generalizing equations for spherical surfaces and lenses to toric surfaces and lenses.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

For several years it has been known that the production rate of tears declines as age increases. Reports suggest that this reduction is more apparent in females than in males. Using a noninvasive method we report that a significant linear reduction in precorneal tear film stability occurs between the ages of 8 and 80 years. However, we found no significant differences in tear film stability between males and females.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Oculogyric crisis developed in a 21-year-old girl after 5 oral doses of 10 mg of metoclopramide. The symptoms were relieved by i.v. administration of diphenhydramine hydrochloride. Although ocular side effects of metoclopramide are rare, it can induce an alarming oculogyric crisis in some sensitive subjects. The mechanism of oculogyric crises is unclear but the characteristics of the condition and some known causes are discussed. Advice is given on optometric management.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Dichoptic color mixing has been a controversial issue for nearly two centuries. The first dispute arose from the fact that dichoptic color mixtures occur only under certain conditions. A later controversy arose over the implications of dichoptic color mixtures to color vision theories. The present consensus is that dichoptic color mixtures occur under conditions which apparently minimize chromatic differences between the two monocular impressions. However, dichoptic mixtures do not match the corresponding monoptic mixtures. Dichoptic mixtures appear dimmer, and if a green light is mixed with either a red or violet light, then the dichoptic mixture appears greener relative to the monoptic mixture.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID