Improving Fixational Stability in Cases of Central Vision Loss

Poor fixation stability is one of the primary challenges to high-resolution in vivo imaging of human retina in cases of central vision loss. We tested the hypothesis that careful design of fixation targets may improve fixation stability. The ability to fixate on a visual target was measured by an eye-tracking camera. In participants without eye disease, target type, target-to-scotoma size ratio and presence or absence of an artificially generated scotoma were manipulated, and the effect on fixation was analysed. A significant interaction effect between target type and scotoma-to-target size ratio was seen in healthy participants, suggesting the optimal target type and size may be dependent on the degree of central vision loss. Data of Stargardt patients were difficult to obtain, paralleling difficulties in retinal imaging. Despite these difficulties, for the patient with least advanced disease, there were indications that instructions, target-type and practice with the task all contributed to improved stability. This has applications for allowing high-resolution imaging procedures to characterise disease progression in conditions of retinal degeneration.