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Overnight Orthokeratology

ABSTRACT:Purpose;Orthokeratology is defined as the temporary reduction in myopia by programmed application of rigid gas-permeable contact lenses.
New reverse geometry contact lens dedigns and materials have led to a renewed interest in this field. The purpose of this study is to assess visual,
Topographic, and corneal thickness changes in subjects under going overnight orthokeratology.Methods:Ten myopic subjects(mean age,25.9±3.9 Years) were recruited for a 50-day trial of overnight orthokeratology using
Reversgeometry rigid contact lenses.After commencing lens wear,subject were examined on days 1,7,14,30,and60 at several times thoughout the day.
High and low-contrast logarithm of the minimum angle of resolution (logMAR) visual acuity, monocular subjective refraction,autorefraction,
Autokeratometry, coneal topography, corneal thickness, and slit lump examinations were performed at each session.Result: Eight subjects
Completed the study, Both high-and-low-contrast uncorrected visual acuity
Improved significantly by day 7.The mean change in uncorrected high contrast visual acuity at day 60 was -0.55±0.20 logMAR(mean at day 60, -0.03±-0.16; Snellen 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 autorefraction were significantly reduced from baseline at day 60(mean change in subjective refraction,+1.83±1.23D; mean cyange in autorefraction,+0.64±0.52D)Corneal topography showed significant central flattening(mean change in apical radius,+0.20±0.9mm ; mean change in shape factor,-0.11±0.18 at day60).The central cornea also showed significant thinning (mean change,-12±11μm at day 60).All visual,refractive and topographic outcomes were sustained over the course of an
8-h day.Conclutions:Overnight orthokeratology is an effective means of temporarily myopia. The possible mechanism of corneal remodeling through
central corneal thinning is discussed.