Effects of foveal and eccentric viewing on the resolution and contrast thresholds of individual letters

Mohd `Izzuddin Hairol, Nor Azizah Abd-Latif, Patricia Low, Wei Ping Lim, Jean Yee Aik, Sharanjeet-Kaur

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Letter recognition is regularly assessed in clinical and experimental settings using a set of letters, either with single letters that are presented successively or with a string of letters that is presented within a single trial. The aim of the present study was to determine resolution thresholds and contrast thresholds for the recognition of each of 7 Sheridan-Gardiner letters that were presented at the central fovea and different retinal eccentricities. Using a method of constant stimuli with a 7-alternative forced-choice paradigm, we measured resolution thresholds for high-contrast letters and contrast thresholds for fixed-sized letters. Measurements were made at the central fovea and at 0.5, 1.0, 2.0, and 4.0° in the lower visual field. Results indicated that the resolution threshold for high-contrast letters (in logMAR) increased approximately linearly with increasing eccentricity (slope =.13, SD=.01). Separate analyses for each letter revealed that their resolution thresholds at a particular eccentricity differed by up to.43 logMAR. However, contrast thresholds for individual letters, scaled for eccentricity, for all retinal locations tested did not differ significantly. Our findings have implications in clinical settings where measurements of visual acuity are performed with a limited number of letters, but they complement the use of low-contrast charts for measurements of contrast sensitivity for letter recognition in the periphery.

Original languageEnglish
Pages (from-to)183-192
Number of pages10
JournalPsychology and Neuroscience
Volume8
Issue number2
DOIs
Publication statusPublished - 1 Jun 2015

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Contrast Sensitivity
Visual Fields
Visual Acuity
Recognition (Psychology)

Keywords

  • High-contrast letters
  • Low-contrast letters
  • Psychometric function
  • Resolution threshold
  • Retinal eccentricity

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Neuroscience(all)

Cite this

Effects of foveal and eccentric viewing on the resolution and contrast thresholds of individual letters. / Hairol, Mohd `Izzuddin; Abd-Latif, Nor Azizah; Low, Patricia; Lim, Wei Ping; Aik, Jean Yee; Sharanjeet-Kaur.

In: Psychology and Neuroscience, Vol. 8, No. 2, 01.06.2015, p. 183-192.

Research output: Contribution to journalArticle

Hairol, Mohd `Izzuddin ; Abd-Latif, Nor Azizah ; Low, Patricia ; Lim, Wei Ping ; Aik, Jean Yee ; Sharanjeet-Kaur. / Effects of foveal and eccentric viewing on the resolution and contrast thresholds of individual letters. In: Psychology and Neuroscience. 2015 ; Vol. 8, No. 2. pp. 183-192.
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