Repeatability of subjective refraction in myopic and keratoconic subjects: Results of vector analysis

Thomas W. Raasch, Kenneth B. Schechtman, Larry J. Davis, Karla Zadnik

Research output: Contribution to journalArticle

50 Scopus citations

Abstract

This paper evaluates the repeatability of refraction in keratoconus patients and normal myopes, using representations of spherocylindrical power that are theoretically valid. Data consist of test-retest refraction data from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study and similar data from normal myopes. Dioptric powers are transformed to an orthogonal vector representation of dioptric power. The metric of change is the dioptric difference between test and retest. The median difference between test and retest in keratoconus patients is four to six times larger than in normal myopes. Refraction over a rigid contact lens on a keratoconic cornea improves repeatability but remains approximately twice as large as in normal myopes. The methods demonstrated here possess advantages over previous methods and provide a more valid comparison between test and retest and between different subject groups. The repeatability of refraction in keratoconus patients is substantially worse than in normal myopes.

Original languageEnglish
Pages (from-to)376-383
Number of pages8
JournalOphthalmic and Physiological Optics
Volume21
Issue number5
DOIs
StatePublished - Aug 7 2001

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