The effect of gaze angle on visual acuity in infantile nystagmus

Dunn, Matthew ORCID: https://orcid.org/0000-0002-0295-2182, Debbie Wiggins, Debbie, Woodhouse, Joy Margaret ORCID: https://orcid.org/0000-0002-7149-5077, Margrain, Thomas Hengist ORCID: https://orcid.org/0000-0003-1280-0809, Harris, Christopher M. and Erichsen, Jonathan Thor ORCID: https://orcid.org/0000-0003-1545-9853 2017. The effect of gaze angle on visual acuity in infantile nystagmus. Investigative Ophthalmology and Visual Science 58 (1) , pp. 642-650. 10.1167/iovs.16-20370

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Abstract

Purpose: Most individuals with infantile nystagmus (IN) have an idiosyncratic gaze angle at which their nystagmus intensity is minimized. Some adopt an abnormal head posture to use this “null zone,” and it has therefore long been assumed that this provides people with nystagmus with improved visual acuity (VA). However, recent studies suggest that improving the nystagmus waveform could have little, if any, influence on VA; that is, VA is fundamentally limited in IN. Here, we examined the impact of the null zone on VA. Methods: Visual acuity was measured in eight adults with IN using a psychophysical staircase procedure with reversals at three horizontal gaze angles, including the null zone. Results: As expected, changes in gaze angle affected nystagmus amplitude, frequency, foveation duration, and variability of intercycle foveation position. Across participants, each parameter (except frequency) was significantly correlated with VA. Within any given individual, there was a small but significant improvement in VA (0.08 logMAR) at the null zone as compared with the other gaze angles tested. Despite this, no change in any of the nystagmus waveform parameters was significantly associated with changes in VA within individuals. Conclusions: A strong relationship between VA and nystagmus characteristics exists between individuals with IN. Although significant, the improvement in VA observed within individuals at the null zone is much smaller than might be expected from the occasionally large variations in intensity and foveation dynamics (and anecdotal patient reports of improved vision), suggesting that improvement of other aspects of visual performance may also encourage use of the null zone.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
Publisher:	Association for Research in Vision and Ophthalmology
ISSN:	0146-0404
Funders:	Nystagmus Network (UK)
Date of First Compliant Deposit:	8 December 2016
Date of Acceptance:	22 November 2016
Last Modified:	17 Jun 2023 06:23
URI:	https://orca.cardiff.ac.uk/id/eprint/96732

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