A Pilot Study of the Effect of Silicone-Hydrogel Lenses and Marketed Multipurpose Solutions on Human Epithelial Barrier Function

Abstract

Purpose:: 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.

Methods:: 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, P_dc, in nm/sec was calculated. The ratio of the test solution P_dc to the control solution P_dc served as the principal outcome measure.

Results:: The P_dc 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 P_dc ratio of 286 and demonstrated grade 4 staining in the test eye vs. grade 1.5 for the control. P_dc 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.

Conclusions:: 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.

Clinical Trial:: www.clinicaltrials.gov NCT00407238

Keywords: contact lens • cornea: clinical science • ocular irritancy/toxicity testing