Patients With AMD Exhibit Strong Central Bias, Reduced Fixation Stability

Patients with age-related macular degeneration (AMD) demonstrate shorter saccadic amplitudes and a pronounced central bias during scene viewing, according to research published in Vision Research.

Researchers assessed viewing biases and explored visual salience among patients with AMD (n=17; mean [SD] age, 78.2 [4.3] years; 14 women), age-matched control group participants (n=17; mean [SD] age, 76.9 [7.2] years; 11 women) and a second control group consisting of young adults (n=17; mean [SD] age, 23.8 [2.5]years; 8 women). Patients underwent visual acuity (VA) measurements, fundoscopy, and optical coherence tomography (OCT) imaging. Participants with AMD were treated with 3 monthly anti-vascular endothelial growth factor (VEGF) injections prior to participating in the study. 

Participants viewed a total of 20 photographs of outdoor scenes for a total of 10 seconds each. During scene viewing, the team observed eye tracking behaviors and evaluated fixation stability, assessing group differences with regard to scene coverage and observer bias toward the center of the scenes. Parcellated local image regions of the photographs were used to assess the independent effects of visual salience on fixation probability.

According to the report, patients with AMD exhibited reduced fixation stability, requiring saccades with shorter amplitudes during viewing. Central bias was more pronounced among patients with AMD compared with participants in the age-matched control group and the cohort of young adults. Horizontal saccades were similar among patients with AMD (48.7%), age-matched control individuals (49.7%) and young adult control group participants (51.9%). 

“The unconstrained nature of our free-viewing task allowed subjects to adopt a viewing style that they deemed fit. AMD patients’ less explorative viewing behavior may be due to impairments caused by their scotomata,” according to the study authors. “Note that differences in viewing behavior between AMD patients and age-matched controls are likely to be task dependent.”

Study limitations include a small sample size and short duration.