Preferred retinal locus profile during prolonged fixation attempts

Abstract

Objective: The retinal area or location used during any fixation attempt defines the preferred retinal locus (PRL). It is presumed that during prolonged fixation attempts there may be various representative reference points within the PRL area. This study aims to clarify this presumption.

Design: Prospective, nonrandomized, observational case series.

Participants: Sixty-five eyes of 41 patients from the University of Nottingham, Queen's Medical Centre Retina and Low Vision Clinics.

Methods: A total of 65 eyes of 41 patients from the University of Nottingham, Queen's Medical Centre Retina and Low Vision Clinics were assessed for PRL using the Macular Integrity Assessment (MAIA) microperimetry equipment (CenterVue, Padova, Italy). The MAIA allows automatic calculation for 2 points named PRL_initial (PRLi), which is calculated after the first 10 seconds of fixation, and PRL_final (PRLf), which is calculated after the completion of all fixation attempts during the microperimetry test.

Results: Estimates of PRLi and PRLf were produced for all patients. Forty-six (71%) eyes were classified as having stable fixation; 40 of the 46 eyes (87%) had both PRLs location over the fovea centralis. Nineteen of 65 eyes (29%) were classified as having unstable or relatively unstable fixation; different PRLi and PRLf locations were found in 18 (95%) of the 19 eyes, including 13 (68%) with central geographic atrophy secondary to dry age-related macular degeneration. The mean rate of change was 5.3 units in fixation per unit change in distance in both PRLi and PRLf.

Conclusions: The representative points during prolonged fixation attempts may vary at different stages of fixation. This is reflected in the characteristics of fixation stability of the patients and presents a possible association with main pathology responsible for low vision.