The Berkeley Orthokeratology Study

To evaluate the relative efficacy of orthokeratology, primarily by assessment of changes in central corneal thickness, astigmatism, visual acuity, endothelial cell density, and corneal curvature. To evaluate the relative safety of orthokeratology, primarily by assessment of changes in central corneal thickness, astigmatism, visual acuity, endothelial cell density, induced corneal edema, and epithelial staining. To assess the duration of any orthokeratology treatment effect. To study the mechanisms by which refractive error and visual acuity changes occur, in particular the contribution that comes from changes in corneal curvature and shape. To determine whether there were any predisposing ocular factors that could be used to predict which subjects will experience changes or complications.