Fixation pattern in Stargardt disease. A longitudinal study

The aim of this study was to examine the development of eccentric fixation in patients with Stargardt disease by long-time follow-up. The fixation locus (FL) positions in the visual field were determined by Tübingen Manual Perimetry by measuring the location of the blind spot and/or the scotoma using a newly developed imaging software. 349 eyes of 175 patients with electrophysiologically confirmed Stargardt disease yielded 725 visual fields measured at baseline and during follow-up. In 77% of the visual fields the FL could be determined unequivocally. From this sample, eccentric fixation was found from the beginning in 113 eyes (32%), while 78 eyes (24%) eyes showed a transition from central to eccentric fixation. 78% had a FL below the scotoma, 10% to the left, 9% to the right and 3% above. In 85% of two consecutive visual fields the FL distance was always < 5°. In a long-term follow-up investigation of fixation locus positions, most Stargardt patients showed a FL below the central scotoma which is considered favorable for horizontal reading. The finding that the patients keep the FL in a small area of the visual field during follow-up indicates a primary tendency for a certain FL, which can be influenced by pre-existent attentional capabilities in the visual field.