Corneal changes after wearing orthokeratology contact lenses

Background. Wearing orthokeratology contact lenses (OCL, Hecht-see free; Hecht, Germany) overnight can change corneal refraction by up to -4.5 dioptre (dpt) based on corneal adaptation to the double reverse surface of the OCL. This allows a temporary independence on glasses or contact lenses. It is known that the central corneal thickness decreases while the corneal thickness in the periphery probably increases. The aim of this study was to investigate the corneal changes of volunteers wearing OCL with in vivo confocal microscopy. Materials and methods. Five young adults (mean 22.8 years, three female, two male) with low to moderate myopia (range -1.75 to -3.5 dpt; sphere equivalent -2.7 +/- 0.59 dpt) were fitted with OCL of reverse-geometry design in both eyes. Lenses were worn in both eyes overnight and were removed immediately in the morning. The volunteers were examined with in vivo confocal microscopy using a combination of Heidelberg retina tomograph II and the Rostock cornea module before wearing the OCL and after the 1(st), 3(rd), 5(th), 7(th), 13(th), 20(th) nights. The central and mid-peripheral total corneal thickness as well as the epithelial thickness were examined in the morning between 7.30 am and 9.30 am. Results. The central and the mid-peripheral epithelial corneal thickness was reduced significantly (p < 0.05) from day 1 to the 13(th) day. This stabilized later until the the examination was concluded. No significant changes (p > 0.05) were found in the central or mid-peripheral total corneal thickness after 25 days of wearing the OCL. Conclusion. Wearing OCL leads to a reduction in the central corneal epithelial thickness. Our inability to find an increase in mid-peripheral total and epithelial corneal thickness may be because the expected increase of the mid-peripheral cornea is limited to a defined area, which makes repeated measurements at a particular point difficult.