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Effect of defocus on contrast sensitivity in myopes and non‐myopes
Author(s) -
Radhakrishnan H.,
Pardhan S.,
Calver R. I.,
O'Leary D. J.
Publication year - 2002
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.2002.00086_12.x
Subject(s) - cycloplegia , contrast (vision) , accommodation , optics , sensitivity (control systems) , spatial frequency , asymmetry , emmetropia , optometry , ophthalmology , refractive error , physics , visual acuity , medicine , quantum mechanics , electronic engineering , engineering
Purpose: Myopes have altered accommodative responses when compared with non‐myopes. We examined the contribution of the optical input to this known altered accommodative response by assessing the defocused contrast sensitivity function in myopes and emmetropes. Methods: Contrast sensitivity (CS) to 20 spatial frequencies was measured under cycloplegia, with up to ±3 D of defocus, in myopes and non‐myopes. The differences in the contrast sensitivity functions as a result of defocus were analysed for the different spatial frequencies in the two groups. In addition, the optimum defocus at which peak contrast sensitivity occurred was compared between the two groups. Results: The loss in contrast sensitivity with defocus was less symmetrical with positive and negative defocus in the myopic group, although there was no latent accommodation left following cycloplegia. Defocus decreased contrast sensitivity symmetrically in non‐myopes. The magnitude of decrease in CS was dependent on the spatial frequency tested, and was significantly different in myopes and non‐myopes at 3 and 6 c deg −1 . Conclusions: Differences in the effects of blur on CS exist between myopes and non‐myopes. Existing models of spherical aberration may explain this asymmetry in positive and negative defocus in myopes.