May 2003
Volume 44, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2003
Can Ocular Spherical Aberrations Predict the Differences in Contrast Sensitivity with Defocus in Myopes?
Author Affiliations & Notes
  • H. Radhakrishnan
    Optometry and Ophthalmic Dispens, Anglia Polytechnic University, Cambridge, United Kingdom
  • R.I. Calver
    Optometry and Ophthalmic Dispens, Anglia Polytechnic University, Cambridge, United Kingdom
  • S. Pardhan
    Optometry and Ophthalmic Dispens, Anglia Polytechnic University, Cambridge, United Kingdom
  • D.J. O'Leary
    Optometry and Ophthalmic Dispens, Anglia Polytechnic University, Cambridge, United Kingdom
  • Footnotes
    Commercial Relationships  H. Radhakrishnan, None; R.I. Calver, None; S. Pardhan, None; D.J. O'Leary, None.
Investigative Ophthalmology & Visual Science May 2003, Vol.44, 2125. doi:
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      H. Radhakrishnan, R.I. Calver, S. Pardhan, D.J. O'Leary; Can Ocular Spherical Aberrations Predict the Differences in Contrast Sensitivity with Defocus in Myopes? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2125.

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

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Abstract

Abstract: : Purpose: Previous studies have shown that ocular aberrations are higher in myopes when compared to emmetropes. We measured contrast sensitivity (CS) at two levels of defocus (+2.00 and -2.00) in a group of myopes and emmetropes. We also measured third order ocular spherical aberration in the two groups in order to examine any possible correlations between predicted and measured CS. Methods: Eight myopes and eight non-myopes took part. CS was measured under cycloplegia with +2.00D and -2.00D defocus for up to 20 spatial frequencies. Ocular aberrations were also measured under cycloplegia using a Shack-Hartmann aberrometer. The measured third order ocular spherical aberration was used to calculate the modulation transfer functions (MTF) for the two levels of defocus on both groups of subjects. Results: In emmetropes the measured CS showed a symmetrical loss to both positive and negative defocus (p=0.474). In myopes the loss of CS with defocus was assymmetrical, with CS loss being significantly higher with positive defocus compared to negative defocus (p<0.001). The obtained MTF's were used to predict CS with defocus for a given spatial frequency using the equation: CS (defocus) = CS (defocus) = CS (infocus) X (|MT (defocus) |/ |MT (infocus) |). Although the above equation slightly overestimates the measured CS, Chi square analysis showed a significant association between the measured CS and the predicted CS values. Conclusions: Differences in the effects of blur on CS exist between myopes and non-myopes. Third order ocular spherical aberration can predict the difference in contrast sensitivity between the two groups.

Keywords: myopia • contrast sensitivity • accommodation 
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