Abstract
Purpose::
Reports on the change in limbal redness following overnight contact lens wear are conflicting. Here, the effect of oxygen transmissibility (Dk/t) on limbal redness and corneal swelling was followed during overnight wear with a set of newer silicone hydrogel (Si-Hy) contact lens materials.
Methods::
Eleven subjects, adapted to daily wear hydrogels, wore Si-Hy lenses made from each of galyfilcon A, lotrafilcon B, and senofilcon A in overnight trials. Limbal redness was assessed prior to and after overnight lens wear according to the Efron grading scale, and corneal thickness was monitored with a calibrated Orbscan instrument. Estimates of the Dk/t at the centre and periphery of these lenses was obtained from recently published measures of Si-Hy Dk values and our own measured thickness profiles of the contact lenses. Statistical analysis was conducted on nine subjects common to all lens types.
Results::
For galyfilcon A, lotrafilcon B, senofilcon A, and no lens respectively, mean (±; SE) change in limbal redness was 0.48 (0.09), 0.40 (0.07), 0.25 (0.05) and 0.06 (0.06), and overnight central corneal swelling was 5.9 (1.3), 4.7 (1.0), 4.3 (1.2) and 2.1 (1.1). The probability that the change in limbal redness and overnight corneal swelling for each lens was greater than no lens simply by chance was less than 0.05 (Fishers LSD). Local Dk/t correlated with both limbal redness and central corneal swelling and these two measured parameters also showed a significant correlation (ANCOVA, p < 0.05).
Conclusions::
Closed-eye wear of the high Dk Si-Hy lenses tested here produced a significant limbal response. The clinical importance of this finding with respect to corneal health during long-term continuous wear remains unclear. Limbal redness measures provide minimal additional statistical information over corneal thickness measures. We note that galyfilcon A is not recommended for closed-eye wear. The results support the accuracy of the recently determined Dk figures.