Fixation Stability and Viewing Distance in Patients with AMD

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Background:

• Normal vision involves effortless adaptation to changing viewing distances.
• Age-related macular degeneration (AMD) affects central vision, often necessitating the use of a preferred retinal locus (PRL).
• Current methods for assessing fixation stability in AMD patients typically use monocular viewing at a fixed distance, which may not reflect real-world conditions.

Purpose of the Study:

• To investigate whether viewing distance influences fixation stability in patients with age-related macular degeneration (AMD).
• To compare fixation stability across different viewing distances (40 cm, 1 m, 6 m) under binocular and monocular conditions in AMD patients and controls.

Main Methods:

• Thirty patients with bilateral AMD and twenty control participants (10 older, 10 younger) were enrolled.
• Fixation stability was measured using a binocular eye-tracker at three distinct viewing distances.
• Measurements were taken under binocular, and monocular (better eye and worse eye) viewing conditions, with stability quantified using bivariate contour ellipse area.

Main Results:

• No significant effect of viewing distance on fixation stability was observed in the AMD group, irrespective of viewing condition (binocular or monocular).
• The control groups (both older and younger) exhibited a similar pattern, with no influence of viewing distance on fixation stability.
• These results indicate consistent ocular motor control across tested distances for both AMD patients and controls.

Conclusions:

• Viewing distance does not alter fixation stability in individuals with age-related macular degeneration.
• Fixation stability assessments performed at a single, fixed viewing distance are likely representative of performance across a range of distances for AMD patients.
• This supports the clinical relevance of current fixation stability measurement techniques for predicting visual task performance in AMD.