Abstract
Purpose: :
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.
Methods: :
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.
Results: :
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.
Conclusions: :
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.
Clinical Trial: :
www.clinicaltrials.gov NCT00560898
Keywords: contact lens • cornea: epithelium