30-Day CW on Corneal Epithelial Barrier Function: RGP vs SiH Lenses

Lin, Meng C. (Clinical Research Center, UC Berkeley School of Optometry), Tan Truong (OD), Thao Yeh (BS), Carol Hsiao (OD), Guang Wei (BS), Audrey V louie (BS), Kenneth A. Polse

PURPOSE: Previous work has shown that 1 day of overnight wear of HEMA and silicon-hydrogel lens wear causes significant changes to epithelial barrier function (EBF). This current study explores the effects of 30-day continuous wear (CW) of gas-permeable (GP) and silicone hydrogel (Si-H) lenses on EBF.

METHODS: EBF was assessed with an automated scanning fluorometer by measuring the permeability of the epithelium to sodium florescence (Pdc) on 67 subjects with no previous CL wear. Subjects were adapted to either GP (tisilfocon A) or Si-H (lotrafilcon A) lenses. Baseline Pdc measurements were obtained: afternoon (PM) followed by next-day morning (AM) measurements. Following baseline assessments, subjects wore their lenses continuously for 30 days; PM and AM Pdc measurements were then repeated.

RESULTS: Pdc analysis was performed on 43 subjects (23 GP; 20 Si-H) who exhibited no central corneal staining at all 4 visits. There was no significant difference in Pdc values between eyes in each lens group for both baseline PM and AM measurements (p > 0.05). In the Si-H lens group, there was a statistically significant increase in corneal epithelial permeability at post 30-day AM visit (within 2 hours of awakening; Mean ± SE lnPdc = -1.694 +0.086 nm/sec), compared with the baseline PM measurement (lnPdc = -2.466 +0.150; p = 0.001). This difference in Pdc values corresponded to 116% increase in corneal epithelial permeability. There was no difference between baseline PM (-2.299 ±0.124) and post 30-day AM Pdc values (-2.395±0.185) in the GP lens group (P > 0.05).

CONCLUSIONS: The results of this study show that there was a substantial decrease in epithelial barrier function during 30-day CW with Si-H lenses, but not with GP lenses. Theses results provide additional clues as to why ocular morbidity associated with Si-H lenses is likely to be caused in part by mechanical interactions between the lens and eye.

KEY WORDS:  Contact lenses - extended wear, Contact lenses - complications, Contact lenses - design/fitting