Purpose: To study the effects of 30-day continuous wear (CW) of silicone hydrogel (Si-H) lenses on epithelial barrier function by measuring the permeability of the corneal epithelium to sodium fluorescence (Pdc).

Methods: 14 subjects with no previous CL wear were adapted to Si-H lenses. Baseline Pdc measurements were obtained, which included afternoon (PM) followed by next-day morning (AM) measurements where one eye was patched overnight until the AM Pdc measurement. Following baseline assessments, subjects wore their lenses continuously for 30 days; PM and AM Pdc measurements were then repeated. All Pdc measurements were obtained using an automated scanning fluorometer.

Results:  There was no significant difference between eyes for baseline PM and AM or CW PM Pdc measurements (p > 0.05).  However, the CW AM Pdc measurements were  -2.184 (ln nm/sec) and -1.908 (ln nm/sec) for patched and unpatched eyes, respectively (p = 0.05). This corresponds to a 37.20% and 71.30% increase in permeability from the baseline PM in the patched and unpatched eyes, respectively. 

Conclusion:  The results of this study show that there is a substantial decrease in epithelial barrier function during CW. Also of interest and possible clinical importance is that the disparity in the corneal epithelial barrier function between patched and unpatched eyes suggests that upon awakening and the resumption of blinking, the accumulated debris/inflammatory cells in the post-lens tear film is mechanically agitated against the corneal epithelium during lens movement.  Therefore, timely tear flushing of trapped debris may be important in maintaining a normal corneal epithelium during CW.