Measuring ocular aberrations and image quality in peripheral vision with a clinical wavefront aberrometer

Abstract

Background:  Clinical aberrometers are accurate, robust instruments for measuring wavefront aberrations for foveal vision but several practical concerns arise when performing aberrometry of the peripheral field. The purpose of this study was to evaluate these concerns experimentally using a physical eye model.

Methods:  A physical model eye was constructed to provide a stable test case that resembled a human eye. Aberrations were measured with a commercial Shack‐Hartmann aberrometer along lines‐of‐sight ranging from zero to 45° of eccentricity. Commercial software for wavefront reconstruction and Zernike analysis was adapted for use with elliptical entrance pupils encountered off‐axis.

Results:  Pupil dimensions estimated from the array of Shack‐Hartmann spots captured by the wavefront sensor followed geometrical optics predictions up to 30° eccentricity. With careful attention to detail, aberration analysis over an elliptical pupil was verified with alternative software. Retinal image quality declined slowly as eccentricity increased due to the eye model's spherical aberration. The total RMS computed from Zernike coefficients overestimated the total RMS computed based on the wavefront error of the elliptical pupil.

Conclusion:  Measurement of off‐axis wavefront aberrations of a model eye over a restricted range of eccentricities is possible with the COAS clinical wavefront aberrometer and auxiliary lenses to correct astigmatism. When central image quality is good, the off‐axis aberrations will have a powerful effect on peripheral image quality. When central image quality is poor, the additional effect of off‐axis aberrations will be minor.

Key words:

• aberration
• aberrometer
• image quality
• peripheral vision

ACKNOWLEDGEMENTS

We appreciate the assistance of Mr. Glenn Herringshaw and his staff in constructing the model eye used in this study.

GRANTS AND FINANCIAL SUPPORT

This work was supported by NIH grant R01‐EY05109. We thank Wavefront Sciences for access to their analysis software CLAS‐2D.