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Abnormal motion processing and binocularity: infantile esotropia as a model system for effects of early interruptions
1Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA.
Insights
Early treatment of infantile esotropia (a common eye misalignment) before age 2 can improve abnormal motion processing. This helps patients achieve better visual development and maintain improvements into adulthood.
Area of Science:
- Neuroscience
- Ophthalmology
- Developmental Biology
Background:
- Infantile esotropia is a common strabismus developing before 6 months of age during critical visual development.
- Patients often exhibit impaired stereopsis and abnormal motion processing, suggesting developmental deficits in visual pathways.
Purpose of the Study:
- To review sensory and motor abnormalities in infantile esotropia.
- To emphasize recent findings on motion visual evoked potentials (VEPs) in infantile esotropia.
Main Methods:
- Review of existing literature on infantile esotropia.
- Analysis of motion visual evoked potential (VEP) recordings in patients with infantile esotropia.
- Comparison of VEPs in treated versus untreated patients and across different treatment timings.
Main Results:
- Infantile esotropia patients show persistent neonatal directional biases in monocular motion VEPs.
- Treatment before age 2 can reduce motion VEP asymmetry, with sustained improvements.
- Treatment after age 2 results in persistent VEP biases into visual maturity.
Conclusions:
- Motion processing deficits in infantile esotropia originate early in the visual pathway.
- Timely intervention (before age 2) is crucial for mitigating motion processing abnormalities.
- Early treatment can lead to lasting improvements in visual function for infantile esotropia patients.
Abstract:
Infantile esotropia, a common form of strabismus with onset prior to 6 months of age, occurs at a time of rapid visual development. While monocular visual acuity is relatively unaffected in these patients, the majority of them fail to achieve fully normal stereopsis. In addition, these patients show a spectrum of abnormalities in their ocular following responses, visual perception and visual evoked potentials (VEPs) that suggest a failure to develop a normal complement of motion processing mechanisms. While abnormalities of of stereopsis have been studied for many years, motion processing in strabismus is a rapidly evolving area of current research. Motion mechanisms are normally binocular and may form a distinct binocular sub-system. This review summarises which is known about sensory and motor abnormalities in infantile esotropia, with special emphasis on recent motion VEP recordings. The monocular motion VEP shows directional biases early in infancy that are consistent with a nasalward/temporalward response bias. Patients with infantile esotropia maintain their neonatal biases beyond the age at which they normally disappear. The motion VEP biases persist into visual maturity in patients whose strabismus is treated after about 2 years of age. Treatment prior to age 2 can lessen the magnitude of the motion VEP asymmetry and these improvements can be maintained into visual maturity. A recording from the striate cortex of a visually deprived macaque monkey indicates that the motion VEP asymmetry arises early in the visual pathway.