Short- and mid-term changes in CORVIS ST parameters in successful, adult orthokeratology patients

Clinical relevance: The analysis of the changes in various biomechanical and tomographic characteristics of the cornea associated with orthokeratology may allow to identify potential mid- and long-term structural alterations, resulting in a better understanding of the governing mechanisms of this procedure and in its optimization. Background: The study aimed at describing short and mid-term changes in CORVIS ST® parameters and indices in orthokeratology (ortho-k), and their diurnal variations. Methods: A prospective observational study was designed in which several CORVIS ST® parameters of 75 new adult participants successfully fitted with overnight ortho-k Seefree® (Conóptica - Hecht Contactlinsen) contact lenses were explored. Measurements were conducted in baseline (BL) conditions and in the morning and evening at the one night (1NM / 1NT), one week (1WM / 1WT) and 3 months (3MM / 3MT) follow-up visits. Results: Statistically significant differences were found in DARatio_2mm, IntRad, ARTh, CBI and TBI following overnight ortho-k, when compared with BL values, with most values reaching stability at 1WM or reverting to BL values at 3MM. The ARTh and CBI parameters showed some of the most significant temporal variations (both p<0.001), probably reflecting the encountered differences in central corneal thickness between BL and 1WM (p=0.010) and between BL and 3MM (p=0.016). In general, corneal rigidity was higher in the morning at all follow-up visits, and decreased during the day. No statistically significant changes in adjusted intraocular pressure values were found. Conclusion: Ortho-k in adults may be considered a safe procedure in terms of short and mid-term changes in CORVIS ST® parameters. The observed alterations in most of the parameters provided by the Corvis ST® probably responded to the well-described changes in corneal pachymetry and tomography, rather than to actual alterations in corneal rigidity.The author David P Piñero has been supported by the Ministry of Economy, Industry and Competitiveness of Spain within the program Ramón y Cajal, RYC-2016-20471.Peer ReviewedPostprint (author's final draft