摘要:

The effect of soft lens design (lathe cut, spun cast) and power (-0.75 to −9.00 D) on central and peripheral corneal swelling was analyzed by measuring the change in corneal thickness after 3 h of eye closure and at mid-day during extended wear. Peripheral swelling was less than central for both lathe cut- and spun cast-type lenses. Significant correlations were found between spun cast lens power and central (r = +0.48) or peripheral (r = +0.32) swelling during eye closure. Small differences in swelling occurred with different power lathe cut lenses (r = −0.19). Correlations of mid-day (open eye) central corneal swelling with lens power were significant for both the spun cast (r = +0.43) and lathe cut (r = −0.53) lenses. However, correlation of peripheral swelling with power was weak. These results indicate that significant lateral diffusion of oxygen and/ or epithelial metabolites may be occurring in the cornea between areas of high and low oxygen tension.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Two healthy subjects (male and female, ages 22 and 25 years) spent 50 h over a period of 7 consecutive weeks training the negative vergence system. The training was performed in two45-min daily sessions, usually immediately before and after the workday. The training was exclusively negative vergence training using devices such as variable vectograms, the aperture rule, the synoptophore, and loose or bar prisms. An extensive examination of the visual systems before, after, and periodically during the training demonstrated that the negative vergences increased at distance by 5.0A and at near by 9.1A (using hand-held prisms, bar prisms, and the synoptophore). The phorias of both subjects became more exophoric or less esophoric at both distance and near by 3.6A (using average of changes on the cover test, von Graefe subjective phoria technique, and the synoptophore). A haploscope equipped with a coincidence optometer showed only small increases in vergence amplitude but confirmed that the lag of accommodation became more stable after the training than it was before. Other testing suggested that the negative relative accommodation, the angle of deviation at both distance and near, positive vergences, the associated phoria, and the slope of the fixation disparity curve changed significantly over the period of training. I conclude that negative vergence training can increase the negative vergence capabilities and also affect the phoria position of the eyes via feedback into the slow vergence system.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Retrospective clinical data from 496 eyes of 256 children attending a low vision clinic were analyzed to determine the relation between different classes of disease that involve visual ' image degradation and astigmatism. Control data comprised refractions from 79 normal division children. Children were classified into groups according to the category of disease (14 groups) and the reported age-of-onset of their visual disability (0 to 13 years, 5 groups). The mean astigmatism for all groups of children with low vision was larger than that of the normals and in most cases the difference was significant at the 95% level. Astigmatism was highest in children with albinism, retinitis pigmentosa, and idiopathic nystagmus. Increased prevalance of astigmatism compared to normals was noted in children having their onset of low vision as late as 13 years of age. In the low vision subjects with-the-rule astigmatism occurred more frequently than oblique or against-the-rule astigmatism and oblique astigmatism more frequently than against-the- rule astigmatism.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Ocular and visual functions were evaluated in 30 insulin-dependent diabetics, aged 12 to 20 years, and 30 age- and sex-matched nondi-abetics. The test and control groups were compared in terms of visual resolution, accommodative ability, color discrimination, functional retinal reserve, and afferent optic nerve function. These results were considered along with the blood-glucose level, crystalline lens, fundus appearance, level of diabetic control, and disease duration. No widespread differences in ocular or visual function were found between the test and control groups. Measures of accommodative ability, functional retinal reserve (photostress recovery time), and blood-glucose level best differentiated the two groups. This study suggests that in-office evaluation of accommodation and functional retinal reserve may be sensitive indicators of early visual functional deficits in the presence of minimal anatomical changes associated with diabetes.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The tear layer thickness profiles of two groups of clinically successful wearers of rigid contact lenses were calculated from the measured anterior corneal surface and posterior contact lens surface characteristics. These profiles showed good agreement with their theoretical values for all parameters considered. However, as large individual variations were found, it was concluded that the tear layer thickness profile is only one of the descriptive factors needed to classify the fitting relations of rigid lenses.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

Toric hydrogel contact lenses are used when spherical lenses prove inadequate at correcting refractive error due to astigmatism. A model of hydrogel contact lens flexure effects allows theoretical investigation of the in situ optical power of toric soft contact lenses. Total meridional power is believed to be the sum of meridional lens power and entrapped tear layer power if any, and not due to lens form or flexure when considering low-minus powered lenses. The clinician should reduce astigmatic power correction both to allow for minus tear lens effects in thicker meridians and to decrease variable visual results due to misrotation.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The corneal endothelium is principally responsible for maintenance of corneal deturgescence. Therefore, compromise of corneal endothelial functional integrity can result in corneal swelling and opacification. Contact lenses constitute a potential insult to the cornea because their wear reduces the oxygen available to that tissue. It has been reported that contact lens wear induces transient as well as permanent morphologic changes in the corneal endothelium. One of the permanent changes reported is referred to as polymegathism, which is a variation in cell size within the endothelial monolayer. Several investigators have suggested that polymegathism reflects a compromised endothelial functional status. Mechanisms proposed to explain contact lens-induced polymegathism include lactate accumulation, changes in pH, and elevation in CO2content. We discuss these possibilities as well as speculate that these poly-megathous shape changes may be a result of decreased endothelial ATP (adenosine triphosphate) levels and disturbed calcium homeostasis due to corneal endothelial hypoxia.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

A public health program instituted and funded by the Government of the Province of New Brunswick and operated by the Provincial Op-tometric Association screened 10,464 grade 1 children using a modified clinical technique (MCT). This paper reports the prevalence of refractive and sensory-motor anomalies in large samples of this child population, all of whom were 6 years of age.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The Native American population has a significant unmet need for eye and vision care. Beginning with the onset of continuous eye care on two reservations in North and South Dakota, a compilation was done of refractive errors and other clinical findings in 1886 Sioux Indians. The results are similar to previous findings in the Navajo, Cheyenne, and Zuni Indians. This paper contributes to the epidemiological characterization of an underserved population, demonstrates the degree of unmet needs before continuous eye care services, and hopefully will aid in the planning, implementation, and evaluation of optometric care for such groups.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

These standards are a revised and updated version of theGuidelines and Standards for Visual Science Libraries Serving Optometric Institutions, a paper first issued by the Association of Visual Science Librarians (AVSL) in 1976. Their purpose is to provide minimum standards as an aid to accreditation bodies and to institutions initiating library service. In this revision, the Standards and Guidelines have been separated physically so that current information can be updated more frequently and easily. The Standards are a qualitative statement about the minimum levels of staff, collections, and services that should be expected from visual science libraries; the Guidelines contain suggested lists of journals and other quantitative data subject to frequent change. The Guidelines are available separately from the AVSL.

ISSN:0093-7002    

出版商:OVID    

年代:1986

数据来源: OVID