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The relationship between word length and threshold character size in patients with central scotoma and eccentric fixation

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Abstract

Background

Understanding limitations on text reading with eccentric fixation is of major concern in low vision research. Our objective was to determine, in patients with a central scotoma, whether threshold character size is similar for different word lengths and paragraphed texts.

Methods

In 19 patients, we retrospectively analyzed the relationship between minimum readable character size for isolated words and text. Isolated letters, two, five, and ten-letter words and a paragraphed text were presented randomly through a scanning laser ophthalmoscope in eight different character sizes.

Results

Threshold character size varied according to the text stimulus (p<0.05). Threshold character sizes for single letters and two-letter words were matched (p>0.99), as were those for five-letter words, ten-letter words, and paragraphed text (p>0.99). Threshold character size for single letters and two-letter words was significantly lower than that measured with other text stimuli.

Discussion

Reading performance is influenced by a variety of factors such as crowding, contextual effects, visual span, degree of oculomotor adaptation needed, and frequency of a defined word. Globally, when reading with a central scotoma, it appears that within word characteristics have more impact than inter-word parameters on threshold character size.

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Acknowledgements

This investigation was supported by the Pro Visu Foundation, the Association pour le Bien des Aveugles, and the Fondation en Faveur des Aveugles, Geneva, Switzerland.

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Authors and Affiliations

  1. Clinique d’Ophtalmologie, Hôpitaux Universitaires de Genève, 22, Alcide-Jentzer, 1211, Genève 14, Switzerland

    Anouk Déruaz, Mira Goldschmidt, Christophe Mermoud, Andrew R. Whatham & Avinoam B. Safran

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  1. Anouk Déruaz
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  2. Mira Goldschmidt
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Correspondence to Anouk Déruaz.

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Déruaz, A., Goldschmidt, M., Mermoud, C. et al. The relationship between word length and threshold character size in patients with central scotoma and eccentric fixation. Graefe's Arch Clin Exp Ophthalmo 244, 570–576 (2006). https://doi.org/10.1007/s00417-005-0111-7

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  • DOI: https://doi.org/10.1007/s00417-005-0111-7

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