Orthokeratology is the programmed application of rigid gas-permeable contact lenses for the temporary reduction of myopia. New reverse geometry contact lens designs and materials have led to a renewed interest in this field. The purpose of this study was to evaluate efficacy and safety profiles of the Hiline orthokeratology contact lens in the temporary reduction of myopia when worn overnight. Methods: Eighty-two myopic subjects (161 eyes; 22 males and 59 females; mean age, 26.5 years, range 12 to 47 years) were recruited from the Tri-Service General Hospital and the Mackay Memorial Hospital. Subjects received a 36-week trial of overnight orthokeratology using reverse geometry rigid contact lenses (using Boston Equalens Ⅱ (oprifocon A) lens material by DreamLens Inc.). The oxygen permeability was 85 by ISO/Fatt and each subject underwent a 4-week follow-up period after discontinuing wearing the lenses. After commencing lens wear, subjects were examined on day 1, weeks 1, 2, 4, 12, 24, and 36, and days 1, 7, and 28 after a final evaluation. Visual acuity was checked with the Snellen chart: autorefraction by the Nikon autokeratometer; corneal topography and corneal thickness with the Orbscan Ⅱ; and slit-lamp examinations were performed to check the corneal condition at each session. Success was defined by improvement in uncorrected Snellen visual acuity of ≥2 lines with ≥20/40 unaided distance Snellen visual acuity at the final evaluation. Results: Sixty-four subjects (128 eyes) completed the study. The uncorrected visual acuity improved significantly by day 7. The success rate at the final evaluation was 100% in both eyes for all subjects and the most significant change occurred between day 1 and day 7. Conclusion: Hiline overnight orthokeratology is an effective way of temporarily reducing myopia. At the final visit, the success rates were 100%. The efficacy of the orthokeratology lens in reducing myopia was confirmed because the lower bound of the 95% confidence interval for subjects was greater than the prespecified 85%. Changes were more prominent in the first week after treatment, particularly on day 1, and reached a maximal effect in week 1. Visual acuity was not correlated to refractive changes. A possible explanation for this is that the autorefractor checks the paracentral cornea, whereas a subject sees through the more central and flatter regions of the cornea. Thinning of the corneal epithelium indicates that a possible mechanism of corneal remodeling is redistribution of the epithelium.