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J. R. Webb, J. R. Paugh, A. C. Ramsey, D. Meadows; Clinical and Epithelial Barrier Function Evidence of Lens Material and Care Solution Bio-Incompatibilities. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2019.
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There is growing concern over potentially significant corneal responses related to some contact lens material-care solution combinations. This investigation evaluated corneal staining and corneal barrier function relative to potential bio-incompatibilities.
Nineteen young, adapted, flexible lens daily wearers were recruited for this randomized, concurrently-controlled, double-masked investigation. New silicone hydrogel or hydrogel lenses, galyfilcon A and omafilcon A, respectively were soaked in pre-conditioned lens cases in 1) a solution containing polyquaternium-1, 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. Corneal staining was assessed immediately following barrier measurement.
The mean Pdc ratios were 2.1 and 9.6 for the PHMB-galyfilcon and PHMB-omafilcon combinations, respectively and 1.9 and 1.2 for polyquaternium-1-galyfilcon and polyquaternium-1-omafilcon combinations, respectively. There were overall differences among combinations (p < 0.001, general linear model), but significant difference only for the PHMB vs. polyquaternium-1 comparison for the omafilcon-A material (p =0.001; Tukey simultaneous test, corrected for repeated measures). The greater ratios mirrored the corneal staining scores on a 0-4 clinical scale. For example, the omafilcon A - PHMB-based combination produced a Pdc ratio of 9.6 (> 900% increase in penetration rate of test vs. control) and demonstrated grade 3 median staining in the test eye vs. grade 1.5 for the control.
The single-drop barrier method appears useful in providing sensitive, objective evidence of corneal compromise. These data suggest that very large differences in lens-solution bio-incompatibilities can exist that mirror corneal staining data relative to corneal compromise.
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