Visual perception and oculomotor control during pursuit eye movements

Nedelchev, Viktor 2022. Visual perception and oculomotor control during pursuit eye movements. MPhil Thesis, Cardiff University. Item availability restricted.

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Abstract

Smooth pursuit is a gaze shifting eye movement that attempts to place the fovea on, or close to, a slowly moving target. Until recently it was presumed that there is negligible position error between the eye and the target during pursuit, and where this did occur, it was eliminated by recruiting saccades (catch-up or back-up saccades). Experiments were conducted to determine how the positional error between the eye and the target varies as a function of target velocity and direction. Results indicated that positional error increased as a function of target velocity, but not direction. Further analyses were performed to examine the proximity of the eye from the target when saccades were initiated. Similar to the previous findings, the positional error corresponding to saccade initiation increased as a function of target velocity but not direction. Furthermore, most saccades made during pursuit were catch-up, rather than back-up saccades. The properties of saccades are well established, however these relate to potentially unnatural viewing conditions, and might not relate to saccades made during pursuit. Experiments showed that the targeting accuracy and precision of saccades during pursuit decreased as a function of target velocity, but not direction. Finally, I have undertaken experiments to determine whether a novel fixation target that recruits optokinetic reflexes can result in a self-stabilising fixation target. Experiments showed that such a target results in improved accuracy but not precision compared to currently adopted fixation targets.

Item Type:	Thesis (MPhil)
Date Type:	Completion
Status:	Unpublished
Schools:	Optometry and Vision Sciences
Subjects:	R Medicine > RE Ophthalmology
Uncontrolled Keywords:	accuracy, back-up saccades, bivariate probability density function, bPDF, catch-up saccades, eye movements, fixation, fixation target, gaze, novel target, oculomotor control, OKN, OKR, optokinetic nystagmus, optokinetic reflex, precision, saccades, sine wave grating, smooth pursuit, stabilisation, visual perception
Date of First Compliant Deposit:	14 February 2023
Last Modified:	05 Jan 2024 05:40
URI:	https://orca.cardiff.ac.uk/id/eprint/156943

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