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J. R. Paugh, D. Krall, A. L. Nguyen, A. C. Ramsey, D. L. Meadows; The Physiological Consequence of Lens Material and Care Solution Bio-Incompatibilities in Humans. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6358.
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This investigation evaluated corneal staining relative to epithelial barrier function and anterior chamber dye diffusion in humans. The objective was to validate the impact of contact lens-solution combinations on corneal staining.
New silicone hydrogel lenses, balafilcon A, were soaked in pre-conditioned lens cases in 1) a polyhexamethylene biguanide (PHMB)-based multipurpose solution and 2) non-preserved saline, which served as the contralateral control. Lenses in the multipurpose solution 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. Corneal staining was assessed immediately following barrier measurement, followed by anterior chamber fluorescence measurements at multiple intervals up to 25 hours following the staining assessment.
All determinations demonstrated consistent behavior (n = 5 separate experiments). Investigator-rated staining was approximately 3 times greater, test eye vs. control, Pdc values were greater in the test eye (up to 450% higher penetration rate) and anterior chamber fluorescence levels were greater and statistically significant in the test eye vs. control up to 5 hours post dye instillation. For example, anterior chamber values, in ng/ml (n = 4 per timepoint) were statistically significant at 0.5, 1.0, 1.5, 2.0, 3.0, 4.0 and 5.0 hrs post rinse (p values ≤ 0.004 at all time points; 1-sample t-test, Bonferroni correction).
The anterior chamber fluorescence data confirm that greater fluorescein dye diffusion occurs when there are higher levels of corneal staining and it is concurrent with increases in dye penetration rates. Future work will further define these relationships for additional material-solution combinations.
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