The Effect of Oxygen Transmissibility on Central & Peripheral Overnight Corneal Swelling

Desmond Fonn, Amir Moezzi, Jalaiah Varikooty, Trefford Simpson

PURPOSE: To compare central and peripheral corneal swelling after 8 hours of sleep in eyes wearing silicone hydrogel lenses with various oxygen transmissibility (Dk/t) values and to eyes without lenses.

METHODS: Twenty nine neophyte subjects wore lotrafilcon A (Dk/t, 175 x 10-9), balafilcon A (Dk/t, 101 x 10-9), galyfilcon A (Dk/t, 86 x 10-9) and senofilcon A (Dk/t, 147 x 10-9) lenses using powers -3.0, -10.0 and +6.0 D in each material on separate nights, in random order, and in one eye only. The contra-lateral eye (no lens) served as the control. Corneal thickness was measured at the centre, 2.3 and 3.4mm from the centre using a digital optical pachometer before lens insertion, immediately after lens removal on waking, then 20, 40 minutes, 1, 2 and 3 hours later.

RESULTS: Averaged for power, there was a significant difference in swelling across lenses, lotrafilcon inducing the least (6.2 ± 2.8 %) and galyfilcon the most (7.6 ± 3.0 %) at the centre (ANOVA, p < 0.001). Corneal swelling was significantly greater in the centre than the periphery (7.0 ± 2.8 % vs. 5.9 ± 2.8%; p < 0.05). The mean central swelling of the control eyes was 4.3 ± 2.6% which was significantly lower than the lens wearing eyes (p < 0.05).

CONCLUSIONS: The differences in central corneal swelling of the experimental eyes are consistent with the differences in oxygen transmission of the silicone hydrogel lenses in this study. Greater corneal swelling in the centre than the peripheral cornea in this study is supported by previous findings using conventional hydrogel or PMMA lenses.

ADDITIONAL COMMENTS: This study was supported by a grant from Ciba Vision