The inter-relationship between magnification, field of view and contrast reserve: The effect on reading performance

Zainora Mohammed, Christine M. Dickinson

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

For the reading task, contrast reserve is defined as the ratio of the letter contrast of the printed letters, to the reader's contrast threshold. Acuity reserve is the ratio of the print size used for the reading task, to the reader's visual acuity. The effects of low contrast reserve on reading performance were investigated at various magnifications, ranging from 3 x to 7.5 x , with the field of view systematically controlled. Eye movements were recorded whilst normally sighted subjects read using the magnifiers. It was shown that with adequate contrast reserve, increasing the field of view improved the reading rate because of the resulting increase in forward saccade length. Conversely, reducing the contrast reserve slowed the reading rate by decreasing the length of forward saccades and increasing the mean fixation duration, suggesting that the perceptual span is reduced at low contrast reserve. This study also shows that when the contrast reserve is low, providing magnification higher than that required for letter recognition (that is, increasing the acuity reserve) will not improve the reading performance. Furthermore, even when the contrast reserve was high, reading rates were lower for the magnifications of 5 x and higher, because increases in saccade length do not match those of the retinal image size at these magnifications. (C) 2000 The College of Optometrists.

Original languageEnglish
Pages (from-to)464-472
Number of pages9
JournalOphthalmic and Physiological Optics
Volume20
Issue number6
DOIs
Publication statusPublished - 2000

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Reading
Saccades
Eye Movements
Visual Acuity

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Health Professions(all)

Cite this

The inter-relationship between magnification, field of view and contrast reserve : The effect on reading performance. / Mohammed, Zainora; Dickinson, Christine M.

In: Ophthalmic and Physiological Optics, Vol. 20, No. 6, 2000, p. 464-472.

Research output: Contribution to journalArticle

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