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JO LaMotte, WH Ridder, T Kuan, J Chang, O Olejnik, J Vehige; The Effect of Artificial Tears With Different CMC Formulations on Contrast Sensitivity . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3151.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Temporal changes in tear film structure can distort the optical wavefront as it passes through the tear layer and reduce contrast sensitivity. Theoretically, any substance applied to the tear layer that alters its structure could affect contrast sensitivity. The purpose of this study is to investigate how different formulations of sodium carboxymethylcellulose (CMC) applied to the tear layer affects contrast sensitivity over time. Methods: Fourteen normal subjects took part in this project. Celluvisc (1.0% high-viscosity CMC) was compared to Refresh Plus (0.5% low-viscosity CMC)(N = 5) or Liquigel (1.0% total CMC made by blending 0.35% high-viscosity with 0.65% medium viscosity CMC)(N = 10). The stimulus, viewed monocularly, was a stationary, vertically oriented, sine wave grating (14 cpd). A temporal, two-alternative, forced-choice paradigm combined with a self-paced method of limits was employed to monitor threshold over time. After baseline data collection, a drop of the artificial tear was applied to the tear layer and the procedure continued for 30 minutes. This allowed continual tracking of the threshold. Results: For the group data, Refresh Plus did not alter contrast sensitivity (P = 0.35). However, after Celluvisc was applied to the eye, there was a significant decrease in contrast sensitivity (P = 0.005). When Celluvisc was compared to Liquigel, both caused a significant decrease in contrast sensitivity (P < 0.0005), however, the contrast sensitivity returned to baseline faster with Liquigel than with Celluvisc (P = 0.02). Conclusion: The results indicate that Refresh Plus does not alter the contrast sensitivity, while the more viscous CMC products do. This may result from distortion of the optical wavefront passing through the tear layer. These results agree with patient observations that Celluvisc results in 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.
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