Abstract
Purpose: :
This study compared the effect of orthokeratology(OK) lens wear on corneal topography and microstructure between the 1 night and 30 night wearers in order to predict any adverse responses of the eyes to long-term OK lens wear.
Methods: :
Nine rhesus monkeys with one eye wearing an OK lens and the fellow eye wearing a rigid gas permeable lens (RGP) were used in this study. The lenses were worn for 11 hours with the measurement of corneal curvature and thickness, and axial components of the eye at 0 night (n=9), 1 night (n=9) and 30 nights (n=6). Histology was performed then.
Results: :
Corneal surface power at 3mm central region was reduced in the OK eye when compared to the RGP eye (p<0.05). Central corneal thickness was only reduced in 30 nights of OK lens wear (p<0.05). Under light microscopy, the 1-night OK or RGP eyes showed normal morphology in all layers of the cornea. The 30-night OK eyes showed a thinned central corneal epithelium and a thickened but less stratified paracentral corneal epithelium when compared to the 30-night RGP eyes. Under electron microscopy, intercellular junctions of corneal epithelium in the 30-night OK eyes were much looser than in the 1-night OK eyes. However, the density and morphology of hemidesmosomes were similar between the OK and RGP eyes at 30 days of lens wear.
Conclusions: :
Overnight orthokeratology can effectively correct myopia by changing the cornea curvature through anterior corneal remodeling. However, a decrease in inter-cellular junctions during a longterm wear may compromise the functions of the corneal epithelium as a frontier mechanical barrier.
Keywords: myopia • microscopy: electron microscopy • contact lens