Abstract
Abstract: :
Purpose: The aim of this study is to examine the effects on the cornea of reversed geometry orthokeratology lens wear (OK) in the rabbit using in vivo confocal microscopy. Methods: 12 NZW rabbits (3–3.5kg) were used for this study and treated according to the ARVO statement for the use of animals in ophthalmic and vision research. Partial membranectomy was performed on all rabbits 1 week prior to confocal microscopy. Baseline control values for corneal epithelial thickness, stromal thickness and corneal epithelial surface cell size were determined for the central and peripheral (temporal) cornea. One week later, one randomly chosen eye was fitted at 10:00am with either a RGP control lens (Menicon Z, Menicon Co. Ltd., Japan) or a reverse geometry OrthoK lens designed for the rabbit eye and made of the same material as the control lens. A handheld slitlamp, blue light and a wratten #12 filter were used to assess the fit on each rabbit. Following 24–hours lens wear, the same eye of each rabbit was scanned again with the confocal microscope. Results: Compared to baseline values, both RGP and OK lenses significantly thinned the central epithelium by respectively 9.8% (p=0.001) and 6.4% (p=0.03). Peripherally a 1% (RGP) and 4% (OK) increase in thickness was found, albeit not statistically significant with the current sample size. Central cell size increased significantly by 5.3% (RGP) and 29% (OK) while peripherally 8.1% (RGP) and 1.6% (OK) decreases were seen. Stromal thickening was comparable for both lenses. Conclusions: This study demonstrates that the rabbit model can be used to study orthokeratology lens wear as it exhibits rapid thinning of the central epithelium and a trend to peripheral thickening similarly to the human. The large and prompt increase in cell size suggests that the central pressure of the OK lens is compressing the central corneal epithelial surface cells, flattening them in the lateral directions; very likely this effect will also occur in the human patient.
Keywords: contact lens • cornea: epithelium • cornea: basic science