Abstract
Abstract: :
Purpose: Most patients with age related macular degeneration (AMD) and dense central scotomas in both eyes adopt a preferred retinal locus (PRL) for eccentric viewing. The majority of patients place their PRL to the left or right of their scotoma in visual field space. However a PRL position in inferior visual space should be optimal as it provides a larger uninterrupted visual span for reading and mobility. It has been suggested (Altpeter, Mackeben 2000) that PRL location is determined by the patient’s ability to allocate attention to areas outside the scotoma. The aim of this study was to compare visual attention at the PRL to attention in the "optimal" location. Methods: 10 Normal vision subjects and 15 AMD patients were recruited. All AMD patients were tested on a Rodenstock scanning laser ophthalmoscope to identify the PRL location in their better eye. For the attention task, subjects had to discriminate the orientation of a black Landolt C presented against a white background. The target was preceded by a grey square presented for 1 sec at the same location. For normal subjects, targets were presented at eight equally eccentric locations at 4 eccentricities. For AMD patients the target was presented at the patient’s PRL, and the optimal location. The duration of the Landolt C varied until the subject achieved 75% correct responses. Fixation was monitored with an eyetracker.Results:In the 10 normal vision subjects performance declined with eccentricity, as expected, but was best along the horizontal meridian. 14 of 15 AMD patients attended better at the PRL than the "optimal" location. The AMD patients had worse visual attention than the age similar normals at an equivalent eccentricity.Conclusions: In normal vision subjects visual attention was best along the horizontal meridian. In AMD patients visual attention was better at the PRL than at the "optimal" location. We can not distinguish whether the PRL develops at the area of best visual attention or if it improves at the PRL through practise. The AMD patients’ visual attention was worse than normal vision subjects at the same retinal eccentricity suggesting the retina around the scotoma does not behave as normal.
Keywords: age-related macular degeneration • low vision • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled