This research was designed to address important issues for the effective prescription of, and training in the use of, magnifiers for reading patients with visual impairment. The emphasis was on the development of simple methods of assessment and training that could be easily implemented, at no great cost, by low vision practitioners in clinical practice. To ensure that the results would be widely applicable, the research focused on subjects with age-related macular degeneration (AMD) using stand magnifiers (being the most common cause of low vision and the most commonly prescribed magnifiers respectively). From this research, modifications to the current methods of reading rehabilitation are suggested to more effectively improve low vision reading for the millions of people with low vision around the world. The magnification and reading performance achieved with the magnifier determined by the fixed acuity reserve method was as valid as that achieved with the magnifier determined by the individual acuity reserve method. The fixed acuity reserve is a simpler method to calculate the required magnification, as it requires only near visual acuity and the patient's goal reading task. This method was primarily used to select the appropriate illuminated stand magnifiers for the subjects participating in the subsequent studies and is recommended for use as the starting point in clinical low vision practice.
The main study of this thesis was a longitudinal investigation of the benefit of large print reading practice on reading performance with stand magnifiers. Instead of the intensive training programs on magnifier use which have been suggested by previous studies, this study aimed to investigate the effect of simple large print reading practice, under either full or restricted field of view (the latter simulated by a practice stand), on reading rate with stand magnifiers for subjects with AMD. The experimental hypothesis was that reading practice prior to the prescription of stand magnifiers would improve reading performance with the stand magnifiers for subjects with AMD. As previous studies have shown, reading rate reduced when a stand magnifier was first introduced. One week of reading practice on large print, with or without a reduced field of view, gave an improvement in reading rate with the stand magnifier for passages of text (such that the reading rates with and without magnifiers were not significantly different). There was a suggestion that this practice may give a more rapid improvement in reading rate than that achieved by the control subjects who did not do any large print reading practice, but this did not reach statistical significance. Even very brief reading with the stand magnifiers by the control subjects gave some improvement in reading rate. Therefore, home or in-office reading practice on large print or with magnifiers is recommended for patients with AMD before magnifiers are prescribed.
Subjects who had neither reading practice nor exposure to the magnifier prior to its prescription required two weeks practice using their stand magnifiers to achieve their maximum reading rate. This suggests that home practice in using stand magnifiers is beneficial and a follow up visit is recommended two weeks after the provision of a magnifier to assess any change in reading rate. If no improvement in the magnifier reading rate is found or the rate is less than the reading rate on large print without a magnifier, further investigations of the patients' vision and/or their magnifier manipulation strategy are necessary.
In the last study, a simple method aimed at alleviating difficulties with magnifier manipulation and navigation, the attachment of a line guide to the base of the stand magnifier, was investigated using both objective methods (recording magnifier movements and reading rate measures) and subjective methods (simple questionnaire). Although there was no improvement in the objective measures of reading or navigation performance with the line guide, more than half of the subjects with low vision preferred to have the line guide on their stand magnifiers. This suggests that the objective measures might not be sensitive enough to predict the subjective response, or that other factors that were not measured in this study influenced subjects' preferences in selecting the line guide (e.g., psychological support provided by the line guide in reading orientation). Clinically, the subjective response of patients to the use of low vision aids as well as their motivation are important criteria for success in low vision rehabilitation. There was a tendency for less experienced users to prefer the line guide to assist their use of the stand magnifier for reading. Therefore, a line guide could be offered as a preliminary training aid when stand magnifiers are first prescribed for AMD patients. Possible improvements to the design of the line guide were identified. Further research is required to assess the benefits of this or similar devices for new magnifier users and to understand the difficulties that people with visual impairment have with page navigation in order to determine improved methods of training navigation strategies.
The unique contribution of this study to the field of low vision rehabilitation is that the benefit of short-term reading practice, on large print or with magnifiers, as simple, cheap methods of enhancing reading performance with stand magnifiers was demonstrated. The results of this study have led to the development of recommendations for assessing and training AMD patients who are prescribed stand magnifiers.
| Identifer | oai:union.ndltd.org:ADTP/264864 |
| Date | January 2003 |
| Creators | Cheong, Allen Ming Yan |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Allen Ming Yan Cheong |
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