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Quantifying the vertical fusion range at four distances of fixation in a normal population.

Ulyat, K., Firth, A.Y. and Griffiths, H.J. (2004) Quantifying the vertical fusion range at four distances of fixation in a normal population. British and Irish Orthoptic Journal, 1. pp. 43-45. ISSN 0068-2314

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Abstract

Aim: To compare the vertical fusional amplitudes in isometropic participants with normal binocular single vision at four distances of fixation: 33 cm, 1 m, 4 m, 6 m.

Methods: Vertical fusion ranges (break point and recovery point) were measured with a Gulden vertical prism bar with the participant fixing a 6/12 Snellen equivalent letter, twice at each distance. Order effects were controlled with randomisation of both fixation distance and prism direction.

Results: Twenty-seven participants were examined (aged 20.4 ± 1.05 years). Base up and base down measurements were similar, therefore measurements were combined to give a total vertical range. Median values for the break points were: 33 cm, 6(Δ) ; 1 m, 6(Δ); 4 m, 5.5(Δ); 6 m, 5.5(Δ); and for the recovery points were: 33 cm, 4(Δ); 1 m, 4(Δ); 4 m, 3.5(Δ); 6 m, 3.5(Δ). The difference was significant between either of the near measures (i.e. 33 cm and 1 m) and either of the far measures (i.e. 4 m and 6 m).

Conclusions: The vertical fusion range appears to be slightly greater at near than distance. However, the difference is not clinically significant. Measurements for distance, in a normal population, appear to be the same whether a fixation distance of 4 m or 6 m is used.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright © 2004 British and Irish Orthoptic Journal
Academic Units: The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > School of Medicine (Sheffield) > Clinical Sciences Division South (Sheffield)
Depositing User: Sherpa Assistant
Date Deposited: 26 Aug 2005
Last Modified: 08 Feb 2013 16:48
Status: Published
Refereed: Yes
URI: http://eprints.whiterose.ac.uk/id/eprint/623

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