Pilot study on the influence of corneal biomechanical properties over the short term in response to corneal refractive therapy for myopia. 2008

José Manuel González-Méijome, and César Villa-Collar, and António Queirós, and Jorge Jorge, and Manuel A Parafita
Department of Physics (Optometry), School of Sciences, University of Minho, Braga, Portugal. jgmeijome@fisica.uminho.pt

OBJECTIVE To study the short-term corneal response to corneal refractive therapy for myopia and correlate it with corneal biomechanical properties as measured with the ocular response analyzer. METHODS Eight eyes from 8 young subjects were fitted with a reverse geometry contact lens, attempting a myopic correction of -4.00 D. Corneal resistance factor and corneal hysteresis (CH) were measured before contact lens fitting with the ocular response analyzer. These parameters were correlated with the degree of change in apical curvature, simulated keratometry, and central corneal thickness after 3 hours of contact lens wear (effect) and 3 hours after lens removal (recovery). RESULTS There was a trend toward a faster effect and faster recovery of the orthokeratologic effect for corneas with less resistance in terms of biomechanical properties. Corneal resistance factor did not correlate significantly, however, with any of the topographic and pachymetric parameters. Conversely, CH was significantly correlated with changes in steep keratometry (0.758; P = 0.029) and central corneal thickness (0.755; P = 0.030) during lens wear and with changes in steep keratometry (-0.835; P = 0.010) during recovery. Overall, higher values of CH meant slower effect and recovery of the orthokeratologic effect. CONCLUSIONS Short-term response of human cornea to corneal refractive therapy is correlated with the biomechanical properties of the cornea. Of the different theories supporting such involvement of corneal response to reverse geometry contact lenses, the most likely one seems to be the one assuming a faster response and faster recovery for corneas with lower resistance. Larger sample studies would be needed to clarify the involvement of corneal biomechanical properties on corneal response to orthokeratology.

UI MeSH Term Description Entries
D008297 Male Males
D009216 Myopia A refractive error in which rays of light entering the EYE parallel to the optic axis are brought to a focus in front of the RETINA when accommodation (ACCOMMODATION, OCULAR) is relaxed. This results from an overly curved CORNEA or from the eyeball being too long from front to back. It is also called nearsightedness. Nearsightedness,Myopias,Nearsightednesses
D010865 Pilot Projects Small-scale tests of methods and procedures to be used on a larger scale if the pilot study demonstrates that these methods and procedures can work. Pilot Studies,Pilot Study,Pilot Project,Project, Pilot,Projects, Pilot,Studies, Pilot,Study, Pilot
D003261 Contact Lenses Lenses designed to be worn on the front surface of the eyeball. (UMDNS, 1999) Lenses, Contact,Contact Lens,Lens, Contact
D003315 Cornea The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed) Corneas
D003941 Diagnostic Techniques, Ophthalmological Methods and procedures for the diagnosis of diseases of the eye or of vision disorders. Diagnostic Technic, Ophthalmological,Diagnostic Technics, Ophthalmologic,Diagnostic Technics, Ophthalmological,Diagnostic Technique, Ophthalmological,Diagnostic Techniques, Ophthalmologic,Ophthalmological Diagnostic Technic,Ophthalmological Diagnostic Technics,Ophthalmological Diagnostic Technique,Ophthalmological Diagnostic Techniques,Technic, Ophthalmological Diagnostic,Technics, Ophthalmological Diagnostic,Technique, Ophthalmological Diagnostic,Techniques, Ophthalmological Diagnostic,Diagnostic Technic, Ophthalmologic,Diagnostic Technique, Ophthalmologic,Ophthalmologic Diagnostic Technic,Ophthalmologic Diagnostic Technics,Ophthalmologic Diagnostic Technique,Ophthalmologic Diagnostic Techniques,Technic, Ophthalmologic Diagnostic,Technics, Ophthalmologic Diagnostic,Technique, Ophthalmologic Diagnostic,Techniques, Ophthalmologic Diagnostic
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D001696 Biomechanical Phenomena The properties, processes, and behavior of biological systems under the action of mechanical forces. Biomechanics,Kinematics,Biomechanic Phenomena,Mechanobiological Phenomena,Biomechanic,Biomechanic Phenomenas,Phenomena, Biomechanic,Phenomena, Biomechanical,Phenomena, Mechanobiological,Phenomenas, Biomechanic

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