title: Morphology, topography, and optics of the orthokeratology cornea.
abstract: The goal of this work was to objectively characterize the external morphology, topography, and optics of the cornea after orthokeratology (ortho-k). A number of 24 patients between the ages of 17 and 30 years (median=24  years) were fitted with Corneal Refractive Therapy® contact lenses to correct myopia between −2.00 and −5.00 diopters (D) (median=−3.41  D). A classification algorithm was applied to conduct an automatic segmentation based on the mean local curvature. As a result, three zones (optical zone, transition zone, and peripheral zone) were delimited. Topographical analysis was provided through global and zonal fit to a general ellipsoid. Ray trace on partially customized eye models provided wave aberrations and retinal image quality. Monozone topographic description of the ortho-k cornea loses accuracy when compared with zonal description. Primary (C40) and secondary (C60) spherical aberration (SA) coefficients for a 5-mm pupil increased 3.68 and 19 times, respectively, after the treatments. The OZ area showed a strong correlation with C40 (r=−0.49, p<0.05) and a very strong correlation with C60 (r=0.78, p<0.01). The OZ, as well as the TZ, areas did not correlate with baseline refraction. The increase in the eye’s positive SA after ortho-k is the major factor responsible for the decreased retinal optical quality of the unaccommodated eye.
authors.affiliation: University of Minho, Clinical and Experimental Optometry Research Laboratory, Center of Physics, School of Sciences (Optometry), Campus de Gualtar, Braga 4710-057, Portugal.
authors.forename: Miguel
authors.initials: M
authors.lastname: Faria-Ribeiro
authors.affiliation: Consejo Superior de Investigaciones Científicas and Universidad de Zaragoza, Instituto de Ciencia de Materiales de Aragón, Facultad de Ciencias, P. Cerbuna, 12, Zaragoza 50009, Spain.
authors.forename: Rafael Navarro
authors.initials: RN
authors.lastname: Belsue
authors.affiliation: Universidad of Murcia, Facultad de Óptica y Optometría, Edificio 35 (Campus de Espinardo), Murcia 30100, Spain.
authors.forename: Norberto
authors.initials: N
authors.lastname: López-Gil
authors.affiliation: University of Minho, Clinical and Experimental Optometry Research Laboratory, Center of Physics, School of Sciences (Optometry), Campus de Gualtar, Braga 4710-057, Portugal.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: González-Méijome
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D003261:Contact Lenses; D003315:Cornea / Q000033:anatomy & histology / Q000473:pathology; D019781:Corneal Topography; D006801:Humans; D009216:Myopia / Q000628:therapy*; D054158:Orthokeratologic Procedures; D011680:Pupil; D012029:Refraction, Ocular; D016896:Treatment Outcome; D055815:Young Adult