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Saccadic strategies in children with hemianopia
L E Mezey1, C M Harris, F S Shawkat
1Department of Ophthalmology, Great Ormond Street Hospital for Children, London, UK.
Developmental Medicine and Child Neurology
|October 10, 1998
Summary
Children with homonymous hemianopia primarily use undershooting eye movements (hypometric saccades) to compensate for vision loss. Overshooting eye movements (hypermetric saccades) were not a consistent strategy in this pediatric group.
Area of Science:
- Neuroscience
- Ophthalmology
- Pediatric Neurology
Background:
- Homonymous hemianopia (HH) is a visual field defect affecting one half of the visual field in both eyes.
- Compensatory eye movement strategies in HH vary, with hypometric saccades commonly observed in adults.
- The development and efficacy of hypermetric saccades as a compensatory strategy in children with HH remain less understood.
Purpose of the Study:
- To investigate the saccadic eye movement strategies employed by children with homonymous hemianopia.
- To determine if hypermetric saccades develop as a compensatory strategy in pediatric HH.
- To compare saccadic strategies in children with HH to those typically reported in adults.
Main Methods:
- Evaluated 10 children (aged 5-16 years) with confirmed homonymous hemianopia using perimetry, pattern visual evoked potentials, and neuroimaging.
- Recorded eye movements using bitemporal electrooculography during a semi-predictable target-elicitation paradigm.
- Analyzed saccade characteristics, focusing on hypometria and hypermetria in relation to the blind visual field.
Main Results:
- Hypermetric saccades were not a consistent compensatory strategy in the studied children with homonymous hemianopia.
- Multiple hypometric saccades directed into the blind visual field emerged as the preferred compensatory strategy.
- This preference for hypometric saccades persisted despite the predictable nature of the visual task and long follow-up periods.
Conclusions:
- Children with homonymous hemianopia predominantly utilize hypometric saccades as their primary compensatory eye movement strategy.
- The development of hypermetric saccades, observed in some adult populations, does not appear to be a consistent or beneficial strategy in this pediatric cohort.
- Understanding these distinct pediatric compensatory mechanisms is crucial for visual rehabilitation and management of homonymous hemianopia in children.