Overnight orthokeratology

Purpose: Orthokeratology is defined as the temporary reduction in myopia by the programmed application of rigid gas-permeable contact lenses. New reve rse geometry contact lens designs and materials have led to a renewed inter est in this field. The purpose of this study is to assess visual, refractiv e, topographic, and corneal thickness changes in subjects undergoing overni ght orthokeratology. Methods: Ten myopic subjects (mean age, 25.9 +/- 3.9 y ears) were recruited for a 60-day trial of overnight orthokeratology using reverse geometry rigid contact tenses. After commencing lens wear, subjects were examined on days 1, 7, 14, 30, and 60 at several times throughout the day. High- and low-contrast logarithm of the minimum angle of resolution ( logMAR) visual acuity, monocular subjective refraction, autorefraction, aut okeratometry, corneal topography, corneal thickness, and slit lamp examinat ions were performed at each session. Results: Eight subjects completed the study. Both high- and low-contrast uncorrected visual acuity improved signi ficantly by day 7. The mean change in uncorrected high contrast visual acui ty at day 60 was -0.55 +/- 0.20 logMAR (mean at day 60, -0.03 +/- 0.16; Sne llen equivalent, 20/19). The mean change in uncorrected low-contrast visual acuity at day 60 was -0.48 +/- 0.26 logMAR (mean at day 60, +0.22 +/- 0.23 ; Snellen equivalent, 20/33). The mean subjective refraction and autorefrac tion were significantly reduced from baseline at day 60 (mean change in sub jective refraction, +1.83 +/- 1.23 D; mean change in autorefraction, +0.64 +/- 0.52 D). Corneal topography showed significant central flattening (mean change in apical radius, +0.20 +/- 0.9 mm; mean change in shape factor, -0 .11 +/- 0.18 at day 60). The central cornea also showed significant thinnin g (mean change, -12 +/- 11 mu m at day 60). All visual, refractive, and top ographic outcomes were sustained over the course of an 8-h day. Conclusions : Overnight orthokeratology is an effective means of temporarily reducing m yopia. The possible mechanism of corneal remodeling through central corneal thinning is discussed.