Abstract
Purpose: :
To examine the effect of short-term overnight conventional rigid gas-permeable (GP) and orthokeratology (OK) contact lens wear on corneal epithelial desquamation rate and Pseudomonas aeruginosa (PA) binding in Asian vs Caucasian eyes.
Methods: :
Sixteen subjects (10 Asian, 6 Caucasian, 18-40 years) were enrolled. Subjects wore a GP lens (J-Contour, Capricornia Contact Lens) in one eye overnight. After at least 2 nights without lenses, an OK lens (BE, Capricornia) was worn in the same eye overnight. Both lens types were made in Boston XO material (Dk 100 ISO units). The other eye acted as a control. The corneal epithelial cell desquamation rate was determined by counting cells collected by saline eyewash, and PA binding to these cells was quantified using a PA binding assay. The eyewash was performed at baseline and within 2 hours of eye opening after lens wear. Corneal topography (Medmont E-300) was measured at each visit. Data were analysed by RM-ANOVA and post hoc t-tests.
Results: :
Corneal topography showed flattening of corneal apical radius after GP (0.03±0.05 mm, p=0.01) and OK (0.10±0.14 mm, p=0.01) lens wear. More flattening was found with OK than GP lenses (p=0.02), showing that an OK effect was achieved. The epithelial desquamation rate reduced from baseline (66.3 ± 33.0 cells) in GP (18.2 ± 8.3), OK (31.8 ± 13.2) and control eyes (27.2 ± 13.4, all p<0.01). PA binding to exfoliated epithelial cells increased from baseline (1.4 ± 0.4 bacteria/cell) in GP (5.4 ± 2.6), OK (4.4 ± 1.1) and control eyes (4.8 ± 2.1, all p<0.01). No significant difference was found between GP and OK lenses in desquamation rate (p=0.52) or PA binding (p=0.76). No difference was found between Asian and Caucasian subjects in any study variables (all p>0.05).
Conclusions: :
Epithelial desquamation rate decreased and bacterial binding increased after overnight lens wear, in both lens-wearing and control eyes following both GP and OK lens wear. No ethnic differences were found in either variable. The over-riding influence on epithelial desquamation and bacterial binding in short-term overnight wear of high Dk GP lenses appears to be eye closure.
Keywords: contact lens • cornea: epithelium • cornea: clinical science