The results suggest that the changes in contrast sensitivity with artificial tear administration were the result of optical aberrations. It appears that long-term use of artificial tears may normalize the tear layer of dry eye disease patients.
Measurement of tear turnover rate using an automated scanning fluorophotometer (FluorotronR) was compared to Schirmer test results without anesthesia in young adults with no known ocular disorder. After the instillation of fluorescein, tear film fluorescence, expressed as fluorescein concentration equivalent, decreased exponentially in a linear fashion with time. The mean tear turnover rate was 30% per minute. Contact lens wearers had higher mean tear turnover rates when compared with non-contact lens wearers, but differences were not statistically significant. Half of tested eyes demonstrated total wetting of Schirmer Tear Test StripsR. Higher mean tear turnover rates were associated with complete wetting of the Schirmer test strips. There was no significant correlation between Schirmer paper wetting of less than 30 mm and fluorescein turnover rate.
These results suggest that Liquigel and Celluvisc alter the tear layer and affect contrast sensitivity. The results agree with patient observations that Celluvisc causes a moderate amount of blur that gradually subsides. In such patients, the shorter duration of blur with Liquigel (about half that of Celluvisc) may be more acceptable. The technique of blending various viscosity CMC materials while maintaining the total CMC concentration of 1.0% may be beneficial in dry eye therapy without causing excessive blur to patients.
This study was conducted to determine the level of automobile window tint that causes a significant reduction of vision for automobile drivers. Contrast sensitivity was measured on 20 participants, of whom 10 were age 20 to 29 years and 10 were age 60 to 69 years, through a stock automobile window (control) and two windows darkened with plastic film. For the younger drivers, a car window with 37% transmittance did not significantly reduce contrast sensitivity, but a darker tint of 18% transmittance reduced contrast sensitivity at higher spatial frequencies. For the older drivers, a tint of 37% transmittance significantly reduced mid-to- high spatial frequency contrast sensitivity. The typical state standard (no tint with less than 35% transmittance) would thus seem to be appropriate for younger drivers; however, further examination of the standard may be necessary in regard to older drivers. Actual or potential applications of this research include guidelines and regulations regarding tinting of automobile windows.
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