Glaucoma is a progressive disease of the optic nerve that can result in visual impairment and in tum inhibit performance on everyday visual tasks. Three connected experimental studies described in this thesis primarily aim to investigate the performance of people with glaucoma on a computer-based task of reading whilst simultaneously recording eye movements. Fifty four patients with bilateral glaucoma and 40 age-similar people with normal vision took part in the experiments. The first study measured change in reading speed when letter contrast is reduced. Results showed that average reduction in reading speed caused by a difference in letter contrast between 100% and 20% is significantly more apparent in patients when compared with age-related people with normal vision and similar cognitive/reading ability (p=0.01). Furthermore, patients more adversely affected by a contrast change were generally those with more severe visual field (VF) defects, poorer contrast sensitivity and poorer visual acuity. A second study explored the relationship between specific locations of the binocular VF and measured reading speed. Results suggested that damage to the inferior left region of the binocular VF was most strongly associated with the reading speed of the patient group. It is possible that this is the VF region used when locating a new line of text and it may be of clinical importance to preserve sensitivity in this area of the VF. The third study used a subset of patients with advanced glaucomatous (N=IS) VF defects to explore the relationship between eye movements and reading speed. Three eye movement measures were explored namely. text saturation (difference between the first and last fixation on lines of text), perceptual span (total number of letters read per number of saccades) and saccadic frequency (total number of saccades made to read a single word presented in isolation in a bespoke lexical decision task). Some, but not all, patients with advanced VF defects read slower than controls but differences in eye movements accounted for much of this variability. These patients also saturated text more during reading when compared to controls (p=O.004) which may explain previously-reported difficulties with sustained reading in glaucoma. In conclusion, principal findings from the studies described in this thesis show, for the first time, that reading speed in patients with glaucoma is particularly affected by changes in text contrast and specific regions of the VF are associated with impaired reading speed. Moreover, eye movement analysis may provide a window into the functional deficits associated with reading in glaucoma
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:591913 |
| Date | January 2013 |
| Creators | Burton, Robyn |
| Publisher | City University London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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