July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Visual crowding in congenital nystagmus, sensory deficit or image motion?
Author Affiliations & Notes
  • Vijay Tailor
    Experimental Psychology, University College London, London, United Kingdom
    Moorfields Eye Hospital, London, ENGLAND, United Kingdom
  • Annegret H Dahlmann-Noor
    Moorfields Eye Hospital, London, ENGLAND, United Kingdom
  • Maria Theodorou
    Moorfields Eye Hospital, London, ENGLAND, United Kingdom
  • John A Greenwood
    Experimental Psychology, University College London, London, United Kingdom
  • Footnotes
    Commercial Relationships   Vijay Tailor, None; Annegret Dahlmann-Noor, None; Maria Theodorou, None; John Greenwood, None
  • Footnotes
    Support  MRC Career Development Award MR/K024817/1 and Moorfields Eye Charity Project Grant ST 16 03 I
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 1080. doi:
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      Vijay Tailor, Annegret H Dahlmann-Noor, Maria Theodorou, John A Greenwood; Visual crowding in congenital nystagmus, sensory deficit or image motion?. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1080.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Congenital nystagmus is a disorder characterised by involuntary eye movements (predominantly horizontal in direction), with associated deficits in visual acuity. These deficits remain once image motion has been reduced, suggesting a sensory deficit that may reflect long-term neural changes. Vision in congenital nystagmus is further disrupted by crowding, a process whereby objects that are visible in isolation become indistinguishable in clutter. We sought to understand whether these crowding effects also derive from a long-term sensory deficit (as in strabismic amblyopia) or due to the image motion (and associated blur) caused by the nystagmus. We examined the origin of these crowding effects by presenting flanker Landolt-Cs adjacent to a target Landolt-C either horizontally or vertically. If nystagmic crowding derives from image motion, crowding should have a disproportionate effect with horizontally arranged flankers (due to the predominantly horizontal eye movements). In contrast, a sensory deficit derived from enlarged receptive fields may be more likely to produce matched crowding effects in each dimension. We drew comparisons to established sensory deficits in amblyopia.

Methods : We recruited 15 participants (9 female, ages 18-50) into 3 groups: nystagmus, amblyopia and controls. Behavioural data was collected for 3 tasks: acuity, horizontal crowding and vertical crowding. Participants identified the orientation of the gap of a Landolt-C presented to the fovea, with thresholds determined using a QUEST that varied gap size to converge on 62.5% correct.

Results : Acuity and crowding thresholds were higher in the nystagmats and amblyopes relative to the controls. Consistent with predictions based on image motion, crowding was larger with horizontally- vs. vertically-positioned flankers for the nystagmats (horizontal: 1.8° ±0.5°, vertical: 1.3° ±0.2°). However, this was also true in amblyopes (horizontal: 3.9° ±2.2°, vertical: 3.3° ±2.2°) and controls (horizontal: 1.0° ±0.2°, vertical: 0.9° ±0.2°).

Conclusions : Overall nystagmats have an elevation in crowding, albeit to a lesser extent than amblyopes. Although the larger increase in crowding with horizontal flankers is consistent with disruptions from image motion, the presence of this difference in all groups suggests a more general sensory component with some degree of horizontal-vertical anisotropy.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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