The clinical relevance of notches in the contrast sensitivity function

N. C. Strang, R. L. Woods, D. A. Atchison*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose. Under controlled laboratory and some clinical conditions, spatial frequency selective minima (notches) have been demonstrated in the contrast sensitivity (CS) function with defocus. Predictions suggest the position and magnitude of notches will depend on 1) the level of defocus, 2) the aberrations of the eye being tested and 3) target field of view. We examined the influence of these three variables on CS function shape in simulated clinical testing. Methods. Six subjects, with varying amplitudes of accommodation, participated in the study. Subjects monocularly viewed the CS display on a monitor under computer control. An adaptive psychometric procedure was used to determine test contrast levels and to estimate CS. Spatial frequencies were measured at approximately 1 cpd intervals. Target field of view was varied between 2.5° and 10°. Surround luminance was approximately matched to the average monitor luminance of 40cd/m2 . CS was measured using a polychromatic ("white") target and natural pupils in bestcorrected, myopic and hyperopic spherical defocus conditions (0.5D steps up to 2D). Results. Notches in the CS function were found with almost all levels of myopic defocus for all subjects. The spatial frequencies of the notches varied with defocus and between individuals. Multiple notches were apparent in some individuals. With hyperopic defocus, notches were only found in subjects with low amplitudes of accommodation. Increasing the target field of view did not significantly effect the magnitude and position of notches. Conclusions-4 Defocus induced notches in the CSF are clinically relevant as they may be mistaken for functional loss or exaggerate the influence of functional loss. The position and magnitude of the notches are dependent on the level of defocus and the aberrations of the patient's eye. Careful refraction should be conducted prior to clinical CS testing. (None).

Original languageEnglish
Pages (from-to)S70
JournalInvestigative Ophthalmology and Visual Science
Volume38
Issue number4
Publication statusPublished - 1997
Externally publishedYes

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

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