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
