Changes in corneal biometry and the associated histology in rhesus monkeys wearing orthokeratology contact lenses.

PURPOSE: This study compared the effect of orthokeratology (OK) lens wear on corneal topography and microstructure between the 1-night and 30-night wearers 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 (RGP) lens 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 at 1 and 30 nights of lens wear. RESULTS: Corneal surface power in the 3-mm central region was reduced in the OK eye when compared with 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 with the 30-night RGP eyes. Under electron microscopy, intercellular junctions of corneal epithelium in the 30-night OK eyes were much looser than those in the 1-night OK eyes. However, the density and morphology of hemidesmosomes were similar between the OK and RGP eyes at 30 nights of lens wear. CONCLUSIONS: Overnight OK can change the corneal curvature through anterior corneal remodeling, resulting in an effective correction of myopia. However, a decrease in intercellular junctions during long-term wear may compromise the functions of the corneal epithelium as a border mechanical barrier.

M cells are involved in pathogenesis of human contact lens-associated giant papillary conjunctivitis.

INTRODUCTION: The objective was to study the pathogenesis of contact lens-associated giant papillary conjunctivitis (CL-GPC). MATERIALS AND METHODS: Twenty-one biopsies of conjunctival giant papillae were obtained from soft contact lens wearers. The tissues were fixed in 4% paraformaldehyde and embedded in paraffin. Sections of 5 microm thickness were used for studies of histology and immunohistochemistry of pan-B and pan-T cell distributions. RESULTS: Conjunctival epitheliums on the top of conjunctiva-associated lymphoid tissue typically lacked goblet cells. Lymphocytes from underlying lymphoid follicle were pressed into intra-epithelial "pockets" formed through epithelial invagination. Under the follicle-associated epithelium, pan-B cells were mostly gathered in the central follicular area and intraepithelial pockets, while CD3-positive T cells were predominantly distributed in parafollicular region, but only a few in the intraepithelial pockets. CONCLUSIONS: Membranous epithelial cells (M cells) play a key role in the pathogenesis of CL-GPC for the binding and translocation of antigen and pathogen.