Preferred retinal locus profile during prolonged fixation attempts

• Published in: Canadian journal of ophthalmology Vol. 48; no. 5; pp. 368 - 374
• Main Authors: Morales, Marco Ulises, MEng, Saker, Saker, MD, Mehta, Rajnikant L., MSc, Rubinstein, Martin, FCOptom, PhD, Amoaku, Winfried M., FRCS, FRCOphth, PhD
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01.10.2013
• Subjects: Aged; Female; Fixation, Ocular - physiology; Humans; Internal Medicine; Male; Ophthalmology; Prospective Studies; Retina - physiopathology; Retinal Diseases - physiopathology; Vision, Low - physiopathology; Vision, Ocular - physiology; Visual Acuity - physiology; Visual Field Tests - methods
• ISSN: 0008-4182; 1715-3360
• DOI: 10.1016/j.jcjo.2013.05.022

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 (PRL i ), which is calculated after the first 10 seconds of fixation, and PRL_final (PRL f ), which is calculated after the completion of all fixation attempts during the microperimetry test. Results Estimates of PRL i and PRL f 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 PRL i and PRL f 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 PRL i and PRL f. 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.