Infantile nystagmus: Investigating the causes and establishing better measures of vision

Ward, Katherine 2025. Infantile nystagmus: Investigating the causes and establishing better measures of vision. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Many interventions and treatments for infantile nystagmus (IN) aim to dampen the IN oscillation in order to improve vision. However, while patients may report subjective improvements in vision, objective measures often show minimal change. An alternative measure that is sensitive to changes in vision resulting from modification of the IN waveform would help better understand visual function in IN and quantify treatment efficacy. This thesis investigated two possible such measures that address the temporal aspect of vision. Firstly, the viewing time required for an optotype at visual acuity to be resolved (‘time to see’) was increased for those with IN relative to a control cohort. It may also be higher in IN when viewing away from the null zone (higher intensity) than towards it (lower intensity), indicating potential as an outcome measure. Secondly, the spatiotemporal contrast sensitivity function (stCSF), describing the limits of the visual system in terms of contrast, spatial frequency, and velocity, was investigated. Psychophysical measurement of the stCSF is arduous, so the feasibility of using vertical optokinetic nystagmus (OKN) as a more time-efficient approach was examined. This showed potential in a control cohort, although further validation and stimulus refinement are required. However, an unanticipated interaction between the IN oscillation and vertical OKN limited its suitability in IN. This thesis also used magnetic resonance imaging to investigate the structure and function of the neural substrates underlying OKN and smooth pursuit in those with and without IN, to explore a theory that IN arises from abnormal persistence of subcortical OKN. Results suggested considerable overlap between the neural basis of IN oscillations, OKN, and smooth pursuit. Furthermore, there was evidence suggesting that cortical thickness and/or volume may be increased in areas of the dorsal pathway and premotor cortex in IN. These findings will provide the basis for future, higher-powered studies.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Optometry and Vision Sciences
Uncontrolled Keywords:	infantile nystagmus, eye movements, psychophysics, eye tracking, MRI
Date of First Compliant Deposit:	9 May 2025
Last Modified:	09 May 2025 15:46
URI:	https://orca.cardiff.ac.uk/id/eprint/178185

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