Assessing inter-ocular fixational eye movements throughout the lifespan.

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Background:

• Fixational eye movements (FEMs) are crucial for maintaining clear vision.
• Understanding age-related changes in FEMs is important for diagnosing visual disorders.

Purpose of the Study:

• To assess how binocular and monocular viewing conditions affect FEMs in different age groups.
• To investigate the impact of age on fixation stability, saccades, and drift velocity.
• To determine if inter-ocular FEMs are age-dependent.

Main Methods:

• Recruited 68 healthy participants across three age groups: children (3-9), adolescents (10-19), and adults (20-73).
• Collected FEMs using a high-resolution video-based tracker under binocular viewing (BV), monocular viewing right eye (MV_RE), and monocular viewing left eye (MV_LE).
• Quantified fixation stability, saccade characteristics (frequency, amplitude, disconjugacy), and inter-saccadic drift velocity, along with inter-ocular fixation stability.

Main Results:

• Fixation instability and saccade amplitudes were higher in children compared to adults.
• Inter-saccadic drifts increased in adults.
• Vergence stability was better in binocular viewing due to binocular summation across all age groups.
• Inter-ocular fixation stability and vergence stability showed no significant age-related differences.

Conclusions:

• FEMs exhibit age-related variations, particularly in fixation instability and saccade characteristics.
• Inter-ocular FEMs demonstrate remarkable stability across different ages, unaffected by viewing conditions.
• Inter-ocular FEMs present a promising, age-independent biomarker for evaluating FEM abnormalities in conditions such as amblyopia.