Evaluation of a new quantitative technique to assess the number and extent of preferred retinal loci in macular disease.

Patients with scotomas due to macular disease may use more than one preferred retinal locus (PRL) for fixation. We have developed and evaluated an objective, quantitative technique to determine the number of PRLs used during an episode of fixation and the extent of each locus. In five of eight adults with macular disease our techniques consistently indicated the presence of multiple PRLs. Patients with multiple PRLs were more likely to have suffered recent vision loss in the tested eye. Our technique describes fixation more fully than the traditional method of calculating a single bivariate contour ellipse area.