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J. Q. Hall, Jr., J. R. Paugh, M. C. Peinovich, A. C. Ramsey, D. Meadows; A Pilot Study of the Effect of Silicone-Hydrogel Lenses and Marketed Multipurpose Solutions on Human Epithelial Barrier Function. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5400.
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There is increasing evidence that certain contact lens material-solution combinations induce clinically meaningful corneal compromise. This was a pilot investigation, using barrier function determination as a sensitive measure of corneal compromise, to objectively quantitate these lens-solution bio-incompatibilities.
Six young, adapted hydrogel daily lens wearers were recruited for this randomized study. New silicone hydrogel lenses (balafilcon A and lotrafilcon B) were soaked in pre-conditioned lens cases in 1) a polyquaternium-1-based solution, 2) a PHMB-based solution, or 3) non-preserved saline, which served as the contralateral control. Lenses in the multipurpose solutions were soaked 6-8 hours (test condition) and control lenses were soaked for 2 hours (active control). At 2 hours of wear epithelial barrier function was determined using the single drop method and a scanning fluorometer. The fluorescein penetration rate, Pdc, in nm/sec was calculated. The ratio of the test solution Pdc to the control solution Pdc served as the principal outcome measure.
The Pdc ratios ranged from slightly less than 1.0 (parity; both solutions) to as much as 286 (only for the PHMB-based solution), indicating an enormous range in dye penetration rate. The greater ratios mirrored the corneal staining scores on a 0-4 clinical scale. For example, the balafilcon A - PHMB-based combination produced a Pdc ratio of 286 and demonstrated grade 4 staining in the test eye vs. grade 1.5 for the control. Pdc ratios for the three lens-solution combinations averaged 65.79, 2.31 and 1.0 for the balafilcon A-PHMB, lotrafilcon B-PHMB and lotrafilcon B-polyquaternium-1 lens-solution combinations, respectively.
The single-drop barrier method appears useful in providing sensitive, objective evidence of corneal compromise. These pilot data suggest that very large differences in lens-solution toxicities can exist and further work is required with additional lens-solution combinations to precisely establish the statistical and clinical differences.
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