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Ron Tutt, Arthur Bradley, Carolyn Begley, Larry N. Thibos; Optical and Visual Impact of Tear Break-up in Human Eyes. Invest. Ophthalmol. Vis. Sci. 2000;41(13):4117-4123.
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purpose. The purpose of this study was to examine the optical and visual impact
of tear break-up.
methods. Optical quality of the eye was assessed during periods of nonblinking
by quantifying vessel contrast in the fundus image and by monitoring
the psychophysical contrast sensitivity and the spatial distribution of
tear thickness changes by retroillumination. All measures were obtained
from three eyes either with or without a soft contact lens.
results. A noticeable decrease in retinal vessel contrast and contrast
sensitivity were observed soon after a blink. Both of these measures of
optical quality of the eye showed a similar pattern of image
degradation both with and without a soft contact lens. Although
trial-to-trial variability was considerable, sample means show that
image contrast in the low spatial frequency range can drop to between
20% and 40% of initial values after 60 seconds of nonblinking.
Retroillumination of the tear film showed local intensity fluctuations
that progressively spread across the pupil with increasing time after
conclusions. Optical aberrations created by tear break-up contribute to the decline
in image quality observed objectively and psychophysically. The decline
in image quality that accompanies tear break-up may be a direct cause
of the blurry vision complaints commonly encountered in dry-eye
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