PURPOSE: To compare the overnight corneal swelling in response to a silicone hydrogel (SiH) toric contact lens with that from a traditional hydrogel toric and a SiH spherical lens.
METHODS: This investigation was a two-phase, prospective, contralateral-eye, non-dispensing trial. A total of twenty-three daily wear adapted contact lens wearers were recruited. In the first phase of this study, twenty subjects wore the SiH (balafilcon) toric lens in one eye and the SiH (balafilcon) spherical lens in the other. In the second phase, twenty subjects, comprising 17 of those who participated in phase 1, wore the SiH toric in one eye and the hydrogel (etafilcon) toric in the other. Lenses were worn overnight for a minimum of 8 hours and corneal thickness was measured with the Pacscan software system (Orbtech Inc) before and immediately after eye opening. Corneal thickness values at selected sites were averaged to create color-coded swelling maps.
RESULTS: The mean (±SD) % corneal swelling values centrally, 3mm superior and 3mm inferior to the corneal centre in phase 1 were 3.94 (± 2.0), 3.48 (± 2.81) and 3.65 (± 2.30) respectively for the SiH toric lens and 3.85 (± 2.1), 2.94 (± 2.60) and 4.26 (± 2.05) for the SiH spherical lens. In phase 2, swelling values for the same sites were 4.37 (± 2.6), 2.92 (± 3.04) and 5.09 (± 2.31) for the SiH toric lens and 9.91 (± 4.8), 7.67 (± 3.66) and 8.31 (± 3.00) for the hydrogel toric lens. There was no evidence of a topographical swelling pattern created by thickness differentials of the SiH toric lenses.
CONCLUSIONS: The corneal swelling with the SiH toric lens was comparable to that of the SiH spherical lens, and substantially less than that with the hydrogel toric lens. Overnight swelling across the cornea under the SiH toric lens was within the range that might be considered physiologically acceptable, suggesting that Si-H toric lenses can provide a suitable physiological environment for the cornea during closed-eye wear.
ADDITIONAL COMMENTS: This study was funded by Bausch & Lomb Inc.