An investigation of the role of the scanning laser ophthalmoscope in the assessment of patients with macular disease

Diseases of the macula are the primary cause of blindness in the western world. Given the current lack of effective medical treatment, there is a requirement for investigation of alternative therapeutic modalities. Traditionally, low vision services provide magnifying devices and advice on illumination. However, there have been claims that training is essential for successful rehabilitation. Using the scanning laser ophthalmoscope (SLO), novel techniques have been developed for the investigation of visual function. Validation was undertaken on subjects with normal vision and patients with a variety of central field defects. Microperimetry in patients demonstrated that visual function did not always correlate with fundus appearance. In normals, small inaccuracies of fixation were found to have no measurable influence on the reproducibility of scotoma maps. Measurements of fixation indicated that the ability to maintain a steady eye position varied significantly between observers both with normal and low vision. Some patients had exceptionally poor fixation whilst in others it was normal. To minimise the problems of target acquisition due to eye movements, a scrolling text system was developed. Assessment of reading performance at specific retinal locations demonstrated that the ability to recognise letters declined with increasing retinal eccentricity and decreasing text contrast. Patients were notably worse at reading tasks than normal observers. Longitudinal evaluation of visual function was undertaken on patients entered into a low vision training programme. Most patients self-selected a single eccentric retinal location for viewing and no suggested alternative locus could be identified that provided superior performance. Although training improved visual performance, it probably resulted from enhancement of patients' psychological status and skill acquisition. This study has demonstrated the usefulness of the SLO in the functional evaluation of vision and its potential for optimising the use of residual vision in patients with macular disease

Evaluation of a low vision training programme

In some countries, notably the United States and Sweden, intensive training is considered an important adjunct to low vision services in the rehabilitation of the visually handicapped. Recently, such training has been introduced into the United Kingdom. Central to many of the programmes for reading are the techniques of eccentric viewing (EV) and steady eye strategy (SES). Although the techniques have been available for the last 15 years and their justification is widely accepted, to date they have not been validated by scientific studies. Two studies were designed to test the hypothesis that intensive training improves the near vision performance with an optical magnifier. Patients with a severe central defect due to age-related macular degeneration were recruited to study "A" (N=57), and patients with a less severe defect to study "B" (N=43). One training and two comparison groups were used in each study. During initial training, 43% of patients believed that EV would be helpful for simple tasks. However, eight months later, only 6.3% in study "A" and 10% in study "B" considered that they had used EV regularly and successfully for reading. The SES had been beneficial to 12.5% in "A" and 0% in "B". There was no significant difference in the near vision performance between the group of trained patients and the comparison groups. A depression index, assessed by the General Health Questionnaire, correlated with neither the method of management nor visual performance for patients in study "A". This is the first time that a trial of this type has been undertaken. It shows that standard management is as effective as training in the rehabilitation of patients. Since standard management is less time consuming it is more cost efficient. These conclusions are relevant to a service for which there is a high requirement and low provision in the United Kingdom