High Resolution Imaging and Fixation Analysis of Eccentric Preferred Retinal Loci in Macular Diseases

The purpose of this study was to characterize the preferred retinal locus (PRL) structure and fixational eye movements in eyes with macular atrophy.

Four participants (1 each with macular atrophy due to congenital rubella, Best macular dystrophy, cuticular drusen with macular atrophy, and Stargardt disease) were studied using adaptive optics scanning light ophthalmoscopy (AOSLO), optical coherence tomography (OCT), OCT angiography (OCT-A), and microperimetry. Imaging sessions were repeated in three of the four participants. PRL and fixation stability were measured with AOSLO. Fixation stability was compared with healthy participants and participants with RHO- and USH2A-related retinitis pigmentosa (RP).

The PRL in participants with eccentric fixation was 0.44 to 1.92 degrees from the anatomic fovea and visual acuity was 20/40 or better. Cones at the PRL were not visible in confocal images, despite normal-appearing and more sensitive cones at greater eccentricities. OCT at the PRL showed intact external limiting membranes but hyporeflective and disrupted inner-segment outer-segment junctions. Fixation stability in participants with eccentric PRLs was no worse than participants with RP, all with foveal PRLs. The eccentric PRL group and the USH2A group with worse visual acuity (20/30 to 20/50) had fixation stabilities that were worse than the healthy controls.

Participants adopt eccentric PRLs with hyporeflective cones and reduced sensitivity despite more sensitive and normal-appearing cones at greater eccentricities, suggesting that foveal proximity is prioritized over cone integrity in establishing a PRL. Fixation stability was similar among the four participants with eccentric fixation and those with RP, indicating that small shifts in the PRL from the anatomic fovea in our participants do not make fixation less stable.