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Measuring contrast sensitivity with inappropriate optical correction*
Author(s) -
Woods Russell L.,
Strang Niall C.,
Atchison David A.
Publication year - 2000
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 - 10.1111/j.1475-1313.2000.tb01122.x
Subject(s) - contrast (vision) , optics , spatial frequency , accommodation , illuminance , astigmatism , maxima and minima , refractive error , optometry , medicine , ophthalmology , mathematics , physics , visual acuity , mathematical analysis
Summary Spatial frequency‐selective minima (notches) in the contrast sensitivity function (CSF) because of defocus can mimic those that occur with ocular disease. We examined the influence of measurement conditions on CSF shape in simulated clinical testing. CSF notches occurred with almost all levels of defocus for all subjects. Multiple notches were found under some conditions. Notches were found with defocus as small as 0.50 D. Effects of induced astigmatism depended on the orientation of the target. Notches were apparent in defocus conditions after stimulus size and room illuminance were modified and when subjects had insufficient accommodation to compensate for hypermetropic defocus. The equivalent of notches was not noted with the Pelli‐Robson chart. As defocus‐induced CSF notches may be mistaken for functional loss, careful refractive correction should be conducted prior to clinical or experimental CSF measurement, even at low spatial frequencies.