Short-Term Effects of Overnight Orthokeratology on Corneal Epithelial Permeability and Biomechanical Properties
Investigative ophthalmology & visual science | 9 May 2013
TN Yeh, HM Green, Y Zhou, J Pitts, B Kitamata-Wong, S Lee, SL Wang and MC Lin
Purpose. To investigate the effects of 30 nights of overnight orthokeratology (OOK) on corneal epithelial permeability (Pdc) and corneal biomechanical properties. Methods. BE Retainer (Precision Technology Services) and Paragon CRT (Paragon Vision Sciences, Inc.) lenses were used. Visits were scheduled approximately 4 hours after awakening at baseline and after 1, 5, 10, 14, and 30 days of treatment. Pdc was measured at baseline and at Day 30, while corneal biomechanical properties and visual acuities (VA) were measured at all visits. Results. Thirty-nine neophytes and soft contact lens wearers completed the study. There was no difference in Pdc between baseline (ln(Pdc) [95% confidence interval (CI)] = -2.65 [-2.80, -2.50]) and Day 30 (ln(Pdc)[CI] = -2.68 [-2.85, -2.50]) (p=0.88). Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF) reduced significantly from baseline (CH [CI] = 10.89 [10.59, 11.19] mm Hg and CRF [CI] = 10.35 [9.99, 10.72] mm Hg) to Day 30 (CH [CI] = 10.59 [10.31, 10.87] mm Hg and CRF [CI] = 9.58 [9.26, 9.89] mm Hg) (p=0.001 for CH and p<0.001 for CRF). Post-treatment VA did not reach baseline targets, and the difference was worse with low-contrast letters. Asians (n=18) had significantly worse VA than non-Asians (n=21) under most conditions through Day 5, and the difference extended through Day 14 with low-contrast letters under mesopic conditions. The percentage of participants who achieved 20/20 uncorrected was 17% Asians and 40% non-Asians after Day 1 and reached 69% Asians and 83% non-Asians at Day 30. Conclusions. 30 nights of OOK did not alter Pdc when measured 4 hours after awakening. OOK caused CH and CRF to decrease, but the changes were not clinically significant compared to diseased and post-surgical cases. Asians, who had lower baseline CH in this study, responded slower to OOK based on early uncorrected VA and over-refraction measurements.
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