Titre du document / Document title

Vector analysis of astigmatism changes by flattening, steepening, and torque

Auteur(s) / Author(s)

ALPINS N. A. ⁽¹⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Cheltenham Eye Centre, 7 Chesterville Road, Cheltenham, Melbourne, Victoria 3192, AUSTRALIE

Résumé / Abstract

Purpose: To understand the effect of astigmatism surgery by analyzing astigmatic changes according to their component parts. Setting: Cheltenham Eye Centre, Melbourne, Australia. Methods: The component parts of the astigmatic changes considered were flattening, steepening, clockwise torque, and counterclockwise torque. Calculations to determine the astigmatic change were performed by vector analysis using rectangular coordinates after doubling the astigmatism and surgical vector axes. A reference axis was used for the resolution of astigmatic change to ascertain its effect along a selected meridian. Results: When correcting astigmatism, the orientations of incisional (tissue addition) or nonincisional (tissue ablation) techniques in any cornea are at right angles to each other. Since differences exist in the measured astigmatism depending on whether it is measured topographically or by manifest refraction, an on-axis correction in one will occur with an off-axis effect in the other. The net result is a reduced flattening effect and a proportionately increased torque effect for the off-axis component. Conclusion: When treatment is applied off one of the four primary axes, the treating vector can be resolved into its component parts of flattening, steepening, and torque. Analyzing changes in this way provides a uniform means of assessing astigmatic changes for all types of cataract and refractive surgery and quantifies the flattening effect when treatment is applied off the intended meridian.

Revue / Journal Title

Journal of cataract and refractive surgery   ISSN 0886-3350   CODEN JCSUEV 

Source / Source

1997, vol. 23, n^o10, pp. 1503-1514 (13 ref.)

Langue / Language

Anglais

Editeur / Publisher

Elsevier, New York, NY, ETATS-UNIS  (1986) (Revue)

Mots-clés anglais / English Keywords

Astigmatism ; Surgery ; Vector method ; Analysis ; Flattening ; Torque measurement ; Result ; Human ; Eye disease ; Vision disorder ; Refractive error ;

Mots-clés français / French Keywords

Astigmatisme ; Chirurgie ; Méthode vectorielle ; Analyse ; Aplatissement ; Mesure couple ; Résultat ; Homme ; Oeil pathologie ; Trouble vision ; Trouble réfraction oculaire ;

Mots-clés espagnols / Spanish Keywords

Astigmatismo ; Cirugía ; Método vectorial ; Análisis ; Aplanamiento ; Medición par ; Resultado ; Hombre ; Ojo patología ; Trastorno visión ; Trastorno refracción ocular ;

Localisation / Location

INIST-CNRS, Cote INIST : 20937, 35400007741771.0090