Abstract
Abstract: :
Purpose: To investigate central and peripheral corneal epithelial changes in neophyte orthokeratology patients after three months of treatment. Methods: Confocal microscopy (ConfoScan3) and ultrasonic pachymetry (Sonogage Corneo–Gage Plus 2) were used to obtain baseline central and peripheral corneal epithelium thickness (CET, PET) measurements on 8 healthy myopic subjects (28 + 4 years; 6 females and 2 males) with a mean spherical equivalent refractive error of –2.31+ 0.89 D; range –1.50 to –4.38 D. Both eyes were fit according to protocol with CKRTM (Boston Equalens II; Dk/t= 85) reverse geometry gas permeable lenses and patients were instructed to wear the lenses overnight for three months. Central measurements were taken with the patient in primary gaze and peripheral measurements were taken inferiorly with the subject in superior gaze (28o above primary gaze). All measurements were repeated after one and three months of continuous lens wear. One eye was chosen for statistical analysis. Measurements were compared using 2–tailed t–tests using the Bonferroni correction factor for multiple comparisons. Results: While individual differences were observed, average mean differences (AMD) between baseline, one month and three month CET and PET measurements showed no statistical difference with the ConfoScan3 or with the Sonogage instruments (p>0.05). For the ConfoScan3, CET and PET at one month was 7.5 + 17.2 µm (AMD + SD) and 2.9 + 17.3 µm and at three months 0 + 10.73 and 4.6 + 15.83 µm respectfully. As for the Sonogage, AMD for CET and PET at one month was –1.8 + 2.7 and 0.2 + 0.1 µm; at three months – 0.4 + 0.96 and 0.1+ 0.79 µm respectfully. All subjects showed significant myopia reduction (p<0.05) at the one month visit and maintained this reduction during the three month visit. Conclusions: Our findings show that myopia reduction after orthokeratology does not appear to be a result of epithelial change as reported by other investigators. It is possible that structural changes within the cornea are not detectable by the methods used. Differences in instrument sensitivity and/or operator error may also partially explain our findings.
Keywords: contact lens • cornea: epithelium • cornea: clinical science