EPITHELIAL PERMEABILITY REFLECTS SUBCLINICAL EFFECTS OF CONTACT-LENS WEAR

Aims-Recently, it was reported by the authors that a single drop fluor ophotometric technique for estimating corneal epithelial permeability (P-dc) to fluorescein is not sufficiently precise for monitoring perme ability changes in individual patients, but may be useful for evaluati ng mean differences in P-dc in population based research. To determine whether this technique provides a more sensitive index of epithelial integrity compared with conventional clinical assessments, the effects of mild corneal trauma on P-dc the slit lamp appearance of the cornea , and corneal thickness (CT) were assessed. Methods-After baseline sli t lamp examinations (SLE) and CT measurements, one randomly chosen eye of each of 32 normal subjects underwent 1 hour of closed eye soft con tact lens (CL) wear while the fellow eye served as a control (no CL). After removing the CL, the SLE and CT measurements were repeated. Then , P-dc to fluorescein was assessed using a single drop fluorophotometr ic method refined to enhance feasibility, precision, and accuracy. Res ults-The mean (95% confidence interval) difference in natural log (P-d c) between 32 pairs of eyes (CL minus no CL) was 0.341 (0.069, 0.613), p = 0.016. By contrast, none of the 32 subjects exhibited corneal epi thelial disruption upon SLE with white light following the closed eye period. Also, no substantial differences were apparent in the corneal swelling response between paired eyes, mean Delta CT (95% CI) = -2.31 (-7.53, 2.91) mu m, p = 0.37. Conclusions-P-dc measurements, used in s tudies of modest sample size, appear capable of detecting average diff erences in corneal barrier function that remain undetectable by SLE or pachymetry.