Original article
Quantifying the vertical fusion range at four distances of fixation in a normal population
Authors:
Katie Ulyat,
Academic Unit of Ophthalmology and Orthoptics, Royal Hallamshire Hospital, Sheffield, GB
About Katie
BMedSci (Orthoptics)
Alison Y. Firth ,
Academic Unit of Ophthalmology and Orthoptics, O Floor, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, GB
About Alison Y.
MSc DBO(T)
Helen J. Griffiths
Academic Unit of Ophthalmology and Orthoptics, Royal Hallamshire Hospital, Sheffield, GB
About Helen J.
PhD DBO
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, 6Δ; 1 m, 6Δ; 4 m, 5.5Δ; 6 m, 5.5Δ; and for the recovery points were: 33 cm, 4Δ; 1 m, 4Δ; 4 m, 3.5Δ; 6 m, 3.5Δ. The difference was significant between either of the near measures (i.e. 33 cm and 1 m) and either of the Tar 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.
How to Cite:
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. DOI: http://doi.org/10.22599/bioj.244
Published on
01 Jan 2004.
Peer Reviewed
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