ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Presbyopic contact lens patients with monocular corrections (monovision) see clearly at all distances by virtue of an interocular suppression of anisometropic blur that occurs regionally between corresponding retinal areas. This suppression fails to occur with small high-contrast targets viewed under low luminance conditions. The effect of target size and contrast upon interocular suppression of blur was quantified by reducing contrast of a bright test spot, viewed binocularly while wearing various plus lenses monocularly, until the out-of-focus image was suppressed. The strength of inter-ocular suppression was equivalent when the plus lens was before either eye. However, after subjects wore a plus lens over their nonsighting eye for one day, interocular suppression of blur became enhanced when the nonsighting eye was blurred, and it became reduced when the sighting eye was blurred. Succcessful monovision subjects suppressed blur at higher contrast levels than did unsuccessful subjects. These results suggest a possible clinical test for quantifying adaptation to monovision.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Ophthalmic lenses are produced in a variety of forms each having unique effects upon visual space. The foundation for evaluating visual space distortion associated with ophthalmic lenses is an understanding of the optical input to the visual system. We developed a photo-graphic technique to evaluate the effects of ophthalmic lenses on optical imagery. This technique uses a pinhole camera and an associated lens holder to simulate the eye-lens relation and provide an eye-referenced view of optical space. A rectilinear grid was photo-graphed through Varilux progressive addition lenses (PAL'S) and with no lenses in place. Comparison of these photographs provides a measure of relative optical space distortion that should closely approximate relative visual distortion under similar viewing conditions. Our technique provides an optical baseline with which more in depth studies of space perception and adaptation may be compared.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Simultaneous objective (based on binocular eye movement record) and subjective (noniusline displacement) measurements of horizontal and vertical fixation disparity were carried out in order to evaluate the reliability of the nonius-line method of measuring ocular deviation. Significant differences were found between the subjective and objective measurements. These differences indicate that the nonius-line method is unreliable for the measurement of ocular deviation or fusional status.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The microbial flora and fauna of 25 high water content nonionic “soft” contact lenses worn by patients on an extended wear basis, 4 hand-cleaned patient-worn lenses, and 4 improperly maintained lenses were compared. Almost all the patient-worn lenses (24 of 25) were free of viable microorganisms, whereas all the hand-cleaned lenses (4 of 4) were contaminated with different microorganisms. This study showed that hand contact is a major source of microbial contamination of a lens and that usually the hand-transported micro-organisms do not survive permanently on the lens in a healthy, normal eye. Improperly maintained lenses demonstrated pathogenic microbial associations. Proof of the eye's potent antimicrobial environment was demonstrated. Thus, microorganism-lens associations are largely due to lens handling and inappropriate maintenance regimens. Typically there are few microorganisms on an extended wear soft lens while it is being worn.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We investigated adult age differences in four measures of visual function: distance acuity, near acuity, stereopsis, and contrast sensitivity. Twenty-four young adults (mean age 19.5 years) and 24 older adults (mean age 68.4 years) participated. Age differences were present in each of the four measures. A step-wise discriminant analysis performed on the four measures revealed that, when the correlations among the measures were taken into account, only contrast sensitivity significantly discriminated young and older adults' performance. The strength of the correlations among the four measures was greater for older adults than for young adults. The results indicated that contrast sensitivity is a useful measure for detecting age-related changes in visual function and that a common mechanism may underlie age differences on various visual tests.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Values of refractive error (RE) observed for subjects and groups depend on the degree to which the measurement method used relaxes accommodation. This affects statistics calculated on RE measurements in predictable ways. Comparing noncycloplegic (NC) with cycloplegic (C) methods, myopia is expected to be more frequent, differences between group means should be less, and correlations and regressions relating RE to other variables may be reduced slightly. Tests based on the categorization of RE will show weaker associations with putative influencing variables. The implications of this are discussed for comparing published studies and choosing measurement methods in epidemiological and genetic studies.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

The effect on accommodation of using plus lenses to fog an eye that is viewing a distant target has been measured with an infrared autorefractor. Sixteen subjects were used; eight hyperopes and eight myopes. There is no difference between the results for the two refractive groups. Intersubject variation did occur; some subjects remained relaxed as the amount of fog was increased, other subjects relaxed initially and then began to accommodate. The data indicate that up to 2 D of fogging can occur before accommodation begins to return to its resting state.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Changes in the contrast sensitivity function (CSF) and corneal thickness of six subjects were monitored during the first 6 months of soft lens wear. Contrast sensitivity suffered a temporary reduction during the first two weeks of wear, subsequently recovering rapidly to normal baseline levels. Corneal thickness increased by 4.9% on the first day of wear, thereafter gradually returning to, but never attaining, prefitting levels. No evidence was found to support complaints of poor vision by long-term soft lens patients. The etiology of the contrast decrements revealed in the early (or adaptation) stages of soft lens wear is discussed.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID