Characteristics of fixation in infantile nystagmus

Amiebenomo, Onyeka

Abstract

Infantile nystagmus (IN) oscillations are known to be multiplanar in some cases however, eye movement assessment for treatment strategies are often done in one plane. Common forms of treatment include maximizing the patients preferred gaze and/or convergence null where the IN oscillation is expected to be least. The main purpose of experiments in this thesis was to evaluate, in two-dimensions, fixational eye movements during fixation at eccentric gaze and at different viewing distances. A probability density function method was used to analyse high speed eye tracking data wherein, the derived 68% isocontour of eye position samples were further analysed to quantify the accuracy and precision of fixation. For the first experiment, data from 18 participants with IN, fixating nine horizontal gaze positions up to ±20°, were evaluated. To investigate further any changes in visual performance with eccentric gaze, experiments thereafter progressed to include psychophysical visual acuity testing at seven horizontal gaze positions up to ±45°, in 12 participants with IN and 14 typical participants. For the second aspect, a third experiment was designed using custom made automated occluder system, alongside eye tracking, to investigate fixational eye movement during convergence and when viewing distance was changed up to 25 cm. Results highlight the idiosyncratic nature of IN between participants and suggests that a difference in waveform at each component of the horizontal plane may not necessarily drive fixation preference at the null. Nonetheless, the amount of IN oscillation, often found to reduce with convergence, was, for the first time, objectively quantified using the fixation precision measure. For typical participants, a preference for an eccentric or convergence position was not objectively found, suggesting that, just like in people with IN, a preference for the null point or primary position of gaze may be attributed to other inherent ocular phenomena.

• Thesis Type: Thesis
• Deposit Date: Nov 6, 2024
• Public URL: https://uwe-repository.worktribe.com/output/11618460
• External URL: https://orca.cardiff.ac.uk/id/eprint/163541/
• Award Date: Oct 27, 2023