International survey of orthokeratology contact lens fitting.

PURPOSE: . To determine the extent of orthokeratology (OK) contact lens fitting worldwide and to characterize associated demographics and fitting patterns. METHODS: . Survey forms were sent to contact lens fitters in 45 countries between January and March every year for 14 consecutive years (2004 - 2017, inclusive). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. RESULTS: . Data were obtained for 295,044 contact lens fits, of which 2,702 were with OK lenses and 292,342 were with other lens types (non-OK). Overall, OK lenses represented 1.2% of all contact lens fits, with significant differences between nations (p < 0.0001), ranging from no fits recorded in Brazil, Egypt, Indonesia, Iran, Lithuania, Nepal and the United Arab Emirates, to 6.0% in The Netherlands. There has been a slight overall increase in OK lens fitting over the survey period (p < 0.0001). OK lenses were fitted to younger persons (OK, 25.0 ± 12.8 years vs. non-OK, 39.8 ± 14.9 years) (p < 0.0001). A higher proportion of males (55%) were fitted with OK lenses versus non-OK lenses (30%) (p < 0.0009). There was a skewed distribution towards OK lenses being fit with higher oxygen permeable materials (p < 0.0001) and on a planned replacement basis (p < 0.0001). CONCLUSIONS: . OK contact lens prescribing is a niche activity, with this lens type typically being fitted in high oxygen permeable materials on a planned replacement basis to younger males. The slightly increasing rate of OK fitting, albeit at a very low level, may be attributed to practitioner interest in the reported myopia control properties of this lens type.

Interaction between Corneal and Internal Ocular Aberrations Induced by Orthokeratology and Its Influential Factors.

PURPOSE: To investigate the interaction between corneal, internal, and total wavefront aberrations (WAs) and their influential factors during orthokeratology (OK) treatment in Chinese adolescents. METHODS: Thirty teenagers (n = 30 eyes) were enrolled in the study; spherical equivalent refraction (SE), corneal curvature radius (CCR), central corneal thickness (CCT), WAs, and the difference in limbal transverse diameter and OK lens diameter (ΔLLD) were detected before and after one-month OK treatment. Every component of WAs was measured simultaneously by iTrace aberrometer. The influential factors of OK-induced WAs were analyzed. RESULTS: SE and CCT decreased while CCR increased significantly (P < 0.01). Higher-order aberrations (HOAs), Spherical aberrations (SAs), and coma increased significantly (P < 0.01). Corneal horizontal coma (Z31-C) and corneal spherical aberrations (Z40-C) increased (P < 0.01). The HOAs, coma, SAs, Z31-C, Z31-T, Z40-C, and Z40-T were positively correlated with SE and CCR (P < 0.01). Z3-1-C showed negative correlations with (ΔLLD) and positive correlations with SE (P < 0.05). CONCLUSIONS: The increase in OK-induced HOAs is mainly attributed to Z31 and Z40 of cornea. Z3-1 in the internal component showed a compensative effect on the corneal vertical coma. The degree of myopic correction and increase in CCR may be the essential influential factors of the increase in Z31 and Z40. The appropriate size of the OK lens may be helpful to decrease OK-induced vertical coma.