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William Ridder, Monisha Paripatyadar, Lisa Wahl; Does Altering the Volume of an Artificial Tear Applied to the Eye Influence Vision?. Invest. Ophthalmol. Vis. Sci. 2013;54(15):900.
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© ARVO (1962-2015); The Authors (2016-present)
Artificial tears (AT) are the most common treatment for dry eye. Several studies have shown that immediately after an AT is placed on the eye vision is degraded for a short time. The purpose of this investigation was to determine if there is a correlation between the volume of AT placed on the eye and the degradation in vision.
Six normal, adult subjects took part in this project. Snellen acuity was better than 20/25 in the eye tested. The subjects had 1 hour of training with the contrast sensitivity (CS) measurement technique before data collection. CS to a 14 cpd sine wave grating (16 ms stimulus presented at 1 sec after the blink) was continually tracked (using a 2 AFC technique) before and after (minimum of 25 minutes) an AT (Refresh Optive, Allergan, Inc.) was applied. The volumes of the ATs applied, randomized across visits, were 25, 45, or 65 µl (Pos D Pipette, Rainin Inst.). The data for different drop volumes were collected on separate days. The magnitude of the loss in normalized contrast sensitivity was compared across drop volumes.
The average loss in normalized CS (mean ± SD) for the drop volumes were: 0.46 ± 0.182, 0.50 ± 0.171, and 0.60 ± 0.293 for 25, 45, and 65 µl, respectively. A paired t-test found a significant difference in the CS loss between the 25 and 65 µl drop sizes (p = 0.05, t = 2.46). No other comparisons were significant (p > 0.05).
The CS decreased as the volume of the applied AT increased. This may be the result of a greater disruption in the tear layer as the AT drop volume increases.
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