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 transmissibilit y on human corneal epithelium during daily lens wear (DW). Design: Prospective, randomized, double-masked, single-center, parallel tre atment groups clinical trial. Participants: Two hundred forty-six patients fitted with: (1) high oxygen-t ransmissible soft lenses (n = 36), (2) hyper oxygen-transmissible soft lens es (n = 135), and (3) hyper oxygen-transmissible rigid gas-permeable (RGP) lenses (n = 75). Intervention: Irrigation chamber to collect exfoliated epithelial surface c ells, confocal microscopy, and tear collection at baseline, 2 weeks, and 4 weeks of DW. Main Outcome Measures: (1) Pseudomonas aeruginosa (PA) binding to exfoliate d corneal epithelial surface cells, (2) central epithelial thickness, (3) s uperficial epithelial cell area, (4) epithelial surface cell exfoliation, a nd (5) tear lactate dehydrogenase (LDH). Results: Four weeks of DW with the high oxygen-transmissible soft lens sign ificantly 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-transmi ssible soft lens wear increased binding significantly less (6.13 <plus/minu s> 2.45 to 7.62 +/- 3.06; P < 0.01), whereas hyper oxygen-transmissible RGP lens wear demonstrated no significant changes (5.91 <plus/minus> 2.40 to 6 .13 +/- 2.17; P = 0.533). No significant change in central epithelial thick ness was found after 4 weeks of DW in either soft lens; however, the epithe lial 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-t ransmissible soft lenses, respectively, and 10.5% with the hyper oxygen-tra nsmissible RGP lens (P < 0.001), Epithelial desquamation significantly decr eased in all groups (P < 0.001), Tear LDH levels increased for all test len ses (P < 0.001). Conclusions: Increased PA binding induced by wear of a conventional soft le ns material is significantly greater than that induced by the new hyper oxy gen-transmissible soft silicone hydrogel lens during DW, However, both soft materials showed significant increases in PA binding as compared with base line controls. By contrast, hyper oxygen-transmissible RGP lens DW did not increase PA binding significantly. Taken together, these findings suggest f or the first time both an oxygen effect as well as a difference between sof t and rigid lens types on PA binding in DW, Ophthalmology 2001;108:1279-128 8 (C) 2001 by the American Academy of Ophthalmology.