Visual Search in Amblyopia: Abnormal Fixational Eye Movements and Suboptimal Sampling Strategies

Area of Science:

• Ophthalmology
• Neuroscience
• Visual Science

Background:

• Microsaccades are crucial for visual perception, preventing fading and aiding scene exploration.
• Amblyopia, or 'lazy eye,' is a developmental disorder affecting visual acuity.
• Understanding eye movement strategies in amblyopia is key to improving visual function.

Purpose of the Study:

• To assess visual search performance in children with amblyopia.
• To investigate the role of microsaccades and saccades in amblyopic visual search.

Main Methods:

• Recruited 21 amblyopic children and 10 controls.
• Recorded eye movements using infrared video-oculography during fixation, blank scene exploration, and visual search tasks.
• Analyzed microsaccades, saccades, and intersaccadic drifts, with slow phase velocities computed for patients with latent nystagmus (LN).

Main Results:

• Amblyopic children identified similar numbers of differences but had longer reaction times compared to controls when using their fellow eye.
• Visual search ability was significantly reduced when using the amblyopic eye, particularly in those with LN and severe amblyopia.
• Reduced frequencies of microsaccades and saccades were observed in both amblyopic and fellow eyes during fixation and visual search.

Conclusions:

• Deficient microsaccade and saccadic activity contribute to impaired visual sampling strategies in amblyopia.
• These deficits are present in both the amblyopic and fellow eyes.
• The findings are more pronounced in amblyopes with latent nystagmus, suggesting earlier binocular decorrelation impacts visual development.