Effects of rigid and soft contact lens daily wear on corneal epithelium, tear lactate dehydrogenase, and bacterial binding to exfoliated epithelial cells

Objective: To determine the effects of lens type and oxygen transmissibility on human corneal epithelium during daily lens wear (DW). Design: Prospective, randomized, double-masked, single-center, parallel treatment groups clinical trial. Participants: Two hundred forty-six patients fitted with: (1) high oxygen-transmissible soft lenses (n = 36), (2) hyper oxygen-transmissible soft lenses (n = 135), and (3) hyper oxygen-transmissible rigid gas-permeable (RGP) lenses (n = 75). Intervention: Irrigation chamber to collect exfoliated epithelial surface cells, confocal microscopy, and tear collection at baseline, 2 weeks, and 4 weeks of DW. Main Outcome Measures: (1) Pseudomonas aeruginosa (PA) binding to exfoliated corneal epithelial surface cells, (2) central epithelial thickness, (3) superficial epithelial cell area, (4) epithelial surface cell exfoliation, and (5) tear lactate dehydrogenase (LDH). Results: Four weeks of DW with the high oxygen-transmissible soft lens significantly increased PA binding from baseline 6.55 ± 3.01 to 8.75 ± 3.05 bacteria per epithelial cell (P < 0.01). By contrast, hyper oxygen-transmissible soft lens wear increased binding significantly less (6.13 ± 2.45 to 7.62 ± 3.06; P < 0.01), whereas hyper oxygen-transmissible RGP lens wear demonstrated no significant changes (5.91 ± 2.40 to 6.13 ± 2.17; P = 0.533). No significant change in central epithelial thickness was found after 4 weeks of DW in either soft lens; however, the epithelial thickness decreased by 9.8% (P < 0.001) with RGP lens wear. Epithelial cell surface area increased 3.3% and 4.1% with the high and hyper oxygen-transmissible soft lenses, respectively, and 10.5% with the hyper oxygen-transmissible RGP lens (P < 0.001). Epithelial desquamation significantly decreased in all groups (P < 0.001). Tear LDH levels increased for all test lenses (P < 0.001). Conclusions: Increased PA binding induced by wear of a conventional soft lens material is significantly greater than that induced by the new hyper oxygen-transmissible soft silicone hydrogel lens during DW. However, both soft materials showed significant increases in PA binding as compared with baseline controls. By contrast, hyper oxygen-transmissible RGP lens DW did not increase PA binding significantly. Taken together, these findings suggest for the first time both an oxygen effect as well as a difference between soft and rigid lens types on PA binding in DW.