This Article  • Full text  • PDF  • Reply to article  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Citation map  • Citing articles on HighWire  • Citing articles on ISI (13)  • Contact me when this article is cited  Related Content  • Related article  • Similar articles in this journal  Topic Collections  • Ophthalmology, Other  • Alert me on articles by topic

Michael K. Smolek, PhD; Stephen D. Klyce, PhD; Edwin J. Sarver, PhD

Arch Ophthalmol. 2002;120:439-447.

Background  The nonsuperimposable mirror-image symmetry of the body (enantiomorphism) is reflected in the wavefront error maps of eyes. Averaging the wavefront errors of right and left eyes has the potential to adversely affect correlations made between wavefront error and visual acuity or other factors. Not only are the results of past studies using Zernike terms suspected of being invalid, there is concern about possible errors in the algorithms used to create customized corneal ablations.

Objective  To compare the results of analysis with and without correction for enantiomorphism.

Methods  Fourteen TMS-1 corneal topographic maps from 7 patients having with-the-rule astigmatism in both corneas were selected for Zernike decomposition to 45 terms. The maps were distributed among 3 groups: 7 right eye maps, 7 left eye maps, and 7 left eye maps in which the topography was transposed about the vertical axial to correct for enantiomorphism (left eye–corrected). The wavefront error difference between the right and left eyes was compared with the difference between the right eyes and the left eyes in which enantiomorphism was corrected (right eye vs left eye–corrected). The left eye wavefront error was then compared with the left eye wavefront error after correction (left eye vs left eye–corrected).

Results  Correcting for enantiomorphism produced a statisticially significant difference in the first 5 radial orders of Zernike terms (P = .02). Of the 45 Zernike terms analyzed, 7 terms were significantly different at the P<.05 level in the right eye vs left eye category, compared with 4 terms in the right eye vs left eye–corrected category. Eleven terms were significantly different at the P<.05 level in the left eye vs left eye–corrected category.

Conclusions  Correcting for enantiomorphism makes the Zernike terms in right and left eyes appear more similar. Failure to correct for enantiomorphism causes certain terms to cancel each other when averaged across right and left eyes. Wavefront error studies that do not consider enantiomorphism, including those used to adjust laser surgical nomograms, will introduce significant errors to certain Zernike terms.

From the LSU Eye Center, Louisiana State University Health Sciences Center, New Orleans (Drs Smolek and Klyce); and Sarver & Associates, Inc, Merritt Island, Fla (Dr Sarver). Dr Sarver has a financial interest in CTView. None of the other authors has proprietary or financial interest in any company or product described in this article.

RELATED ARTICLE

Archives of Ophthalmology Reader's Choice: Continuing Medical Education
Arch Ophthalmol. 2002;120(4):527-528.
FULL TEXT  

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Magnitude and Orientation of Zernike Terms in Patients with Keratoconus
Kosaki et al.
IOVS 2007;48:3062-3068.
ABSTRACT | FULL TEXT  

The Influence of Eyelid Morphology on Normal Corneal Shape
Read et al.
IOVS 2007;48:112-119.
ABSTRACT | FULL TEXT  

Mapping collagen organization in the human cornea: left and right eyes are structurally distinct.
Boote et al.
IOVS 2006;47:901-908.
ABSTRACT | FULL TEXT  

Zernike Polynomial Fitting Fails to Represent All Visually Significant Corneal Aberrations
Smolek and Klyce
IOVS 2003;44:4676-4681.
ABSTRACT | FULL TEXT