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Validating a "pillar and collar" technique for measuring the edge lift of rigid contact lenses. 1998

W A Douthwaite, and M A Hurst
Department of Optometry, University of Bradford, West Yorkshire, United Kingdom.

OBJECTIVE The clinical importance of the edge lift of rigid contact lenses is often neglected, possibly due to previous difficulties in its measurement. A new method of measuring axial edge lift (AEL) and radial edge lift (REL) using standard contact lens verification equipment, such as an optical spherometer, a thickness gauge, and contact lens V gauge, is described. METHODS The technique was validated for trueness (accuracy) and precision (repeatability) by measuring the edge lift of a number of monocurve lenses, manufactured both with and without a normal edge finish. RESULTS Edge lift was measured to an accuracy of 0.01 mm. CONCLUSIONS As long as a mean of eight independent measurements of back optic zone radius (BOZR), sagitta, and one measurement of center thickness are taken, the pillar and collar technique is capable of producing accurate and repeatable measurements of the edge lift of a rigid contact lens.

UI MeSH Term Description Entries
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
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D015203 Reproducibility of Results The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results. Reliability and Validity,Reliability of Result,Reproducibility Of Result,Reproducibility of Finding,Validity of Result,Validity of Results,Face Validity,Reliability (Epidemiology),Reliability of Results,Reproducibility of Findings,Test-Retest Reliability,Validity (Epidemiology),Finding Reproducibilities,Finding Reproducibility,Of Result, Reproducibility,Of Results, Reproducibility,Reliabilities, Test-Retest,Reliability, Test-Retest,Result Reliabilities,Result Reliability,Result Validities,Result Validity,Result, Reproducibility Of,Results, Reproducibility Of,Test Retest Reliability,Validity and Reliability,Validity, Face
D017755 Prosthesis Fitting The fitting and adjusting of artificial parts of the body. (From Stedman's, 26th ed) Prosthesis Adjustment,Adjustment, Prosthesis,Adjustments, Prosthesis,Fitting, Prosthesis,Fittings, Prosthesis,Prosthesis Adjustments,Prosthesis Fittings
D019904 Polymethyl Methacrylate Polymerized methyl methacrylate monomers which are used as sheets, moulding, extrusion powders, surface coating resins, emulsion polymers, fibers, inks, and films (From International Labor Organization, 1983). This material is also used in tooth implants, bone cements, and hard corneal contact lenses. PMMA,Polymethylmethacrylate,Acron,Acrylic Bone Cement,CMW Bone Cement,Implast,Kallocryl K,Lucite,Methyl Acrylic Plastic,Palacos R,Palavit,Perspex,Plexiglas,Plexiglass,Poly(methyl methacrylate),Polymethyl Methacrylate, Isostatic,Polymethyl Methacrylate, Simplex Opaque,Polymethyl Methacrylate, Surgical Simplex Bone Cement, Ammonium Salt,Polymethyl Methacrylate, Surgical Simplex P,Polymethyl Methacrylate, Syndiostatic,Polymethylmetacrylate,Sol,Superacryl,Isostatic Polymethyl Methacrylate,Methacrylate, Polymethyl,Methacrylate, Syndiostatic Polymethyl,Syndiostatic Polymethyl Methacrylate

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