Inattention to nonsuperimposable midline symmetry causes wavefront analysis error

Area of Science:

• Ophthalmology
• Optometry
• Biomedical Engineering

Background:

• The human eye exhibits enantiomorphism, a non-superimposable mirror-image symmetry.
• Averaging wavefront errors between right and left eyes can distort correlations with visual acuity.
• Existing studies using Zernike terms and corneal ablation algorithms may be affected by uncorrected enantiomorphism.

Purpose of the Study:

• To compare the analytical results of wavefront errors with and without correction for ocular enantiomorphism.

Main Methods:

• Corneal topographic maps from 7 patients with regular astigmatism were analyzed.
• Zernike decomposition was applied to 45 terms for right eyes, left eyes, and enantiomorphism-corrected left eyes.
• Wavefront error differences were compared between original and corrected eye maps.

Main Results:

• Correction for enantiomorphism yielded statistically significant differences in the first 5 radial orders of Zernike terms (P=.02).
• Significant differences (P<.05) were observed in 7 Zernike terms when comparing right vs. left eyes, and 4 terms when comparing right vs. corrected left eyes.
• Eleven Zernike terms showed significant differences when comparing left eyes to corrected left eyes.

Conclusions:

• Correcting for enantiomorphism increases the similarity of Zernike terms between right and left eyes.
• Failure to correct for enantiomorphism can cause Zernike terms to cancel out during averaging.
• Wavefront error studies and laser surgical nomogram adjustments must account for enantiomorphism to avoid significant errors.