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

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    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)

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    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)

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    Helen J. Griffiths

    Academic Unit of Ophthalmology and Orthoptics, Royal Hallamshire Hospital, Sheffield, GB
    About Helen J.

    PhD DBO

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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, 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.
    Keywords: Fixation distance, Normal binocular single vision, Vertical fusion range
    DOI: https://doi.org/10.22599/bioj.244
    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
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    Published on 01 Jan 2004.
    Peer Reviewed
    CC BY 4.0

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