Quantifying fixation in patients with Stargardt disease

Fixational eye movements in 60 eyes of 30 patients with ABCA4-associated Stargardt disease were recorded by a Scanning Laser Ophthalmoscope (SLO). The results were quantified by two new fixation quality measures expressing the eccentricity of the preferred retinal locus (PRL) non-parametrically, and fixation stability by a dynamic index. 46 eyes (77%) fixated eccentrically; in 32 eyes (70% of the eccentrically fixating eyes) the PRL was located above the central retinal lesion. PRL eccentricity correlated positively with logMAR visual acuity (r=.72; p<.0001) and negatively with fixation stability (r=-.58; p<.0001). Multiple PRL were found only in three eyes.