December 2002
Volume 2, Issue 10
Free
OSA Fall Vision Meeting Abstract  |   December 2002
Where is the far-point in aberrated eyes?
Author Affiliations
  • Larry N. Thibos
    School of Optometry, Indiana University, Bloomington, IN, USA
  • Arthur Bradley
    School of Optometry, Indiana University, Bloomington, Indiana, USA
  • Raymond A. Applegate
    Optometry, University of Houston, Houston, TX, USA
Journal of Vision December 2002, Vol.2, 41. doi:10.1167/2.10.41
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      Larry N. Thibos, Arthur Bradley, Raymond A. Applegate; Where is the far-point in aberrated eyes?. Journal of Vision 2002;2(10):41. doi: 10.1167/2.10.41.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: We sought a method for deducing the far-point of an aberrated eye from an aberration map. Such a method is necessary for successful implementation of wavefront-guided treatments. Method. Accommodation was paralyzed and pupils dilated in both e yes of 100 subjects. Subjective refractions determined the spectacle correction needed to maximize visual acuity for high-contrast letters. Sphero-cylindrical refractive errors were corrected with trial lenses when measuring monochromatic abe r rations (633nm) with a Shack-Hartmann aberrometer. Resulting aberration maps were fit with spherical wavefronts four ways to yield four different estimates of the far point for each eye. Method 1 minimized the RMS error b etween the given wavefro nt and the s pherical wave over the full pupil. Method 2 determined the spherical wavefront which had the same paraxial curvature as the meridionally-averaged curvature of the given aberration map. Method 3 maximized the pupil area over which RMS wavefron t error was less than a criterion level of 1/4 wavelength. Method 4 maximized the pupil area over which the absolute wavefront error was less than 1/4 wavelength. Results: A successful method will yield a far point at infinity sinc e all eyes were emmetro pic when t ested. Method 1 was a clear failure, predicting a mean far point vergence of −0.26D for the study population. The other three methods all yielded far points which, on average, had vergence close to 0D (Method 2: mean=0.0 23 , std=0.296. Metho d 3: mean =0.05 , std=0.33. Method 4: mean=0.004 , std=0.55). Methods 2 and 3 yield standard deviations close to the expected minimum (0.25D) set by the variability of subjective refraction. Conclusion: Three successful methods for u sing an aberration map to locate the far point of the eye have been found. One unsuccessful method is equivalent to the Zernike coefficient for defocus.

Thibos, L. N., Bradley, A., Applegate, R. A.(2002). Where is the far-point in aberrated eyes? [Abstract]. Journal of Vision, 2( 10): 41, 41a, http://journalofvision.org/2/10/41/, doi:10.1167/2.10.41. [CrossRef]
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