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Abnormal Fixational Eye Movements in Amblyopia
Aasef G Shaikh1,2,3, Jorge Otero-Millan4, Priyanka Kumar5
1Daroff-Del'Osso Ocular Motility Laboratory, Louis Stokes Cleveland VA Medical Center, Cleveland, Ohio, United States of America.
Insights
Children with amblyopia (lazy eye) exhibit altered fixational saccades, characterized by larger, less frequent movements. These changes in eye control are linked to amblyopia severity and are independent of abnormal drifts.
Area of Science:
- Ophthalmology
- Neuroscience
- Pediatric Vision
Background:
- Fixational saccades are crucial for maintaining clear vision by repositioning the fovea.
- Neural adaptation can cause visual fading, which fixational saccades help to mitigate.
- Amblyopia, a common cause of childhood blindness, is associated with visual processing deficits and fixation instability.
Purpose of the Study:
- To quantify fixational saccades in children with amblyopia.
- To investigate if observed changes in fixational saccades are related to pathological drifts in amblyopia.
- To correlate alterations in fixational eye movements with amblyopia severity.
Main Methods:
- High-resolution video-oculography was used to record eye movements in 36 pediatric subjects with amblyopia and 11 controls.
- Fixational saccades and drifts were analyzed during both fellow eye and amblyopic eye viewing conditions.
- Data were compared between amblyopic and control groups, and correlations with amblyopia severity were assessed.
Main Results:
- Children with amblyopia showed increased amplitude and decreased frequency of fixational saccades.
- These saccadic alterations correlated significantly with the severity of amblyopia.
- Increased eye position variance during drifts was observed in amblyopic subjects, but was independent of subsequent saccade amplitude.
Conclusions:
- Fixation instability in pediatric amblyopia is quantitatively characterized.
- Impaired fixational saccade properties may stem from abnormal visual processing and neural reorganization in amblyopia.
- Reduced visual feedback during amblyopic eye viewing may contribute to increased drift velocity and eye position variance.
Purpose:
Fixational saccades shift the foveal image to counteract visual fading related to neural adaptation. Drifts are slow eye movements between two adjacent fixational saccades. We quantified fixational saccades and asked whether their changes could be attributed to pathologic drifts seen in amblyopia, one of the most common causes of blindness in childhood.
Methods:
Thirty-six pediatric subjects with varying severity of amblyopia and eleven healthy age-matched controls held their gaze on a visual target. Eye movements were measured with high-resolution video-oculography during fellow eye-viewing and amblyopic eye-viewing conditions. Fixational saccades and drifts were analyzed in the amblyopic and fellow eye and compared with controls.
Results:
We found an increase in the amplitude with decreased frequency of fixational saccades in children with amblyopia. These alterations in fixational eye movements correlated with the severity of their amblyopia. There was also an increase in eye position variance during drifts in amblyopes. There was no correlation between the eye position variance or the eye velocity during ocular drifts and the amplitude of subsequent fixational saccade. Our findings suggest that abnormalities in fixational saccades in amblyopia are independent of the ocular drift.
Discussion:
This investigation of amblyopia in pediatric age group quantitatively characterizes the fixation instability. Impaired properties of fixational saccades could be the consequence of abnormal processing and reorganization of the visual system in amblyopia. Paucity in the visual feedback during amblyopic eye-viewing condition can attribute to the increased eye position variance and drift velocity.
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