ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Recently, concern has been expressed about accommodative facility testing reliability, especially for subjects rated initially as failing. Our study evaluated an extended testing period's effect on reliability. Subjects, ages 8 to 12 years, were tested for an initial 1-min period; to identify two groups; high fails (greater than 6, but less than 11 cpm, N=30) and low fails (less than 6 cpm, N=30), and then for an additional 2 min. Mean rate change analysis showed both high and low fail groups improved their accommodative facility over extended testing (1.29 and 0.87 cpm, respectively), although no significant difference was found between the groups. In contrast, test-retest correlations indicate a higher reliability for the baseline rates among low fail (r=0.720) as compared to high fail (r=0.402) subjects. The difference between groups became more evident when diagnostic classification was monitored over the 3-min testing period, with 73.3% of the low fails remaining low fails, and 43.4% of the high fails reached the pass criterion. The 1-min testing method appears more reliable if the initial rate is less than 6 cpm. For patients whose initial rate is between 6 and 11 cpm, extended testing (1 additional min) may be needed to arrive at an accurate diagnosis, especially if presenting symptoms are absent.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The reliability of estimating the cup to disc (C/D) ratio using a retinal camera photograph was compared to the same task using a photograph taken with the slitlamp and +90 D lens. Twenty observers (10 optometry students, 10 faculty members) were asked to judge the C/D ratio of four eyes by the two photographic methods. When comparing the two clinically accepted photographic methods, statistically significant differences were noted for the vertical dimension estimate in two of four eyes. However, these differences were not clinically significant. C/D ratio estimates with the retinal camera photograph were typically larger than those of the slitlamp and +90 D lens photograph. Neither photographic method provided an advantage or disadvantage to clinicians with different levels of experience.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We evaluated the effectiveness and convenience of microwave irradiation as a method of disinfecting soft contact lenses. Soft contact lenses from each of the four Food and Drug Administration (FDA) categories were placed in sterile vials and immersed in 2 ml of saline which had been contaminated with one of three common species of bacteria. The contaminated lens vials were placed in a standard 600 W microwave oven and exposed to microwave irradiation times ranging from 30 to 180 s. Significant reductions in bacteria colony counts were found after 30 s of microwave irradiation. Few of the bacteria survived 60 s of microwave exposure and none survived 90 s. Our findings indicate that microwave disinfection can be an effective and rapid means of killing bacteria on soft lenses and in the storage solution. However, further studies are necessary to determine the minimum exposure time required, the effect of microwave disinfection on other microorganisms, and the effect of microwave irradiation on contact lens polymers and lens dimensions.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

We studied the relation of postlens squeeze pressure to the clinical fit of hydrogel contact lenses. This relation was statistically significant (p < 0.01) for a variety of contact lenses currently prescribed over a range of thickness, water content, back central optic radius, diameter, and back vertex power. The squeeze pressure provided a useful parameter to describe and compare the clinical fit of hydrogel contact lenses and a model with which the fit of a lens to an eye could be predicted. There was virtually no movement of the contact lenses across the eye when the squeeze pressure was more than –14 mm H2O (–1370 dynes/cm2). However, the mechanics of the lens motion when the squeeze pressure was less than this critical pressure appeared to be related to a more complicated combination of the squeeze pressure and the other forces in the eye-lens system.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

This study assessed the fitting and visual performance of a rigid, gas permeable (RGP), monocentric, alternating bifocal. Fourteen presbyopic eyes each wore 24 different lenses consisting of all combinations of 2 diameters, 2 segment heights, 2 prism ballasts, and 3 fitting relations. The influence of parameter selection on visual performance and the usefulness of clinical measurements in predicting visual performance were determined statistically by multivariate logistic regression. Our results showed that prism, segment height, and the fitting relation can influence distance and near visual performance. Lens movement, postblink segment positioning, and return time were the most useful measured predictors of visual performance.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Fixation disparity may be a symptom of binocular stress or a purposeful error signal to drive vergence eye movements. Two similar units for detecting fixation disparity (Mallett and Sheedy units) are compared and evaluated. The Mallett unit was found to be more reliable, with similar readings in symptom-free subjects, whereas the Sheedy unit gave a larger spread of fixation disparity measurements and appears to be less useful than the Mallett unit for routine clinical use. The exact role of fixation disparity remains unresolved. Fixation disparity has two components in symptomatic subjects; the vergence signal component and an oculomotor imbalance component.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

The time needed to change accommodation from a near to a far target or from a far to a near target (0.457 and 5.486 m) was measured with a psychophysical threshold procedure in 65 U.S. Navy fighter pilots. The age of the pilots ranged from 24 to 44 years. The speed of accommodative change, far-to-near (FN), slowed with age in a statistically significant fashion; however, near-to-far (NF) did not appreciably slow with age. The intrasubject variability was greater FN than NF but there was not a statistically significant dependence of variability upon age.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Serial oxygen flux measurements were obtained from the same cornea of 5 human subjects after exposure to ambient air, a test gas mixture (2% oxygen, balance nitrogen) and 100% nitrogen at 2 individual measurement sessions. Analysis of variance (ANOVA) of the individual flux measurements for the test gas indicates that there were significant differences in corneal oxygen flux rates among subjects and sessions. Referencing the flux data for the test gas to the data for ambient air reduced the variability of data between sessions, although significant intersubject differences were still present. By referencing the flux data for the test gas to the concurrent air and nitrogen data, differences among subjects, as well as sessions, were reduced to the extent that they were not statistically significant. Standardization of data is important in the interpretation of corneal oxygen flux data so that intersubject and intersession differences can be minimized.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

Ultraviolet radiation (UVR) has been demonstrated to be involved in a number of adverse ocular effects. One aspect of UVR-induced corneal stress only recently documented is an alteration of epithelial energy metabolite levels. In this study, in order to examine wavelength and dose dependency issues concerning metabolic effects of UVR, exposures were made at four different wavelengths (290, 300, 310 and 360 nm) and five different mean radiant exposures (0.05, 0.10, 0.15, 0.20, and 0.25 J·cm-2). Pre- and postexposure levels of relative metabolic activity of the corneal epithelium were monitoredin vivoby recording the corneal oxygen uptake rate with a micropolarographic electrode. A paired difference analysis demonstrated a decrease in relative corneal metabolic activity that was both wavelength- and dose-dependent. These relative metabolic effects provide some insight toward the understanding of underlying damage mechanisms, and imply a broader radiant energy susceptibility range of the eye than previously thought.

ISSN:1040-5488    

出版商:OVID    

年代:1989

数据来源: OVID