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Flash visual evoked response binocular summation in normal subjects and in patients with early-onset esotropia before
L E Leguire1, G L Rogers, D L Bremer
1Department of Ophthalmology, Children's Hospital, Columbus, Ohio, USA.
Insights
Binocular summation in young children shows initial facilitation that rapidly declines to adult levels. This process, crucial for developing binocularity, appears to accelerate with surgical alignment in esotropia patients.
Area of Science:
- Ophthalmology
- Developmental Neuroscience
- Pediatric Vision
Background:
- Binocular summation, the enhanced visual response when both eyes are open compared to one, is critical for visual development.
- Understanding the developmental trajectory of binocular summation is essential for identifying visual processing abnormalities in early childhood.
Purpose of the Study:
- To investigate the developmental changes in flash visual evoked response (f-VER) binocular summation in normal children and children with early-onset esotropia.
- To determine the time course of binocular summation development and its relationship to binocular alignment.
Main Methods:
- Recorded flash visual evoked responses (f-VERs) in normal children (1-58 months), normal adults, and children with early-onset esotropia.
- Assessed binocular summation before and longitudinally for 1 year after surgical binocular alignment in esotropic children.
- Used prism lenses in normal adults to investigate the role of binocular misalignment.
Main Results:
- Normal f-VER binocular summation exhibited facilitation (>2.0) at 1 month, decreasing to adult levels by 3.7 months.
- Esotropic children showed similar binocular summation patterns initially, with a rapid decrease to adult levels post-surgery.
- Base-in prism significantly reduced binocular summation in adults, indicating misalignment isn't the cause of early facilitation.
Conclusions:
- The facilitation in f-VER binocular summation during early development may represent a critical process for establishing binocularity.
- This developmental process appears to be closely linked to and potentially accelerated by achieving binocular alignment.
Abstract:
Flash visual evoked responses were recorded and visual evoked response binocular summation was assessed in normal children between the ages of 1 and 58 months, in normal adults and in children with early-onset esotropia before and longitudinally for 1 year after surgical binocular alignment. Normal flash visual evoked response binocular summation started in the range of facilitation (> 2.0) at 1 month of age and decreased to adult levels by 3.7 months of age. The shape of the flash visual evoked response binocular summation function obtained from the patients with early-onset esotropia, appeared similar to that of normal subjects; however, the rapid decrease in flash visual evoked response binocular summation from facilitation to normal adult levels occurred after surgical binocular alignment. In normal adults, flash visual evoked response binocular summation was significantly reduced by a 40-diopter base-in prism, suggesting that binocular misalignment was not the reason for the facilitation in flash visual evoked response binocular summation in either childhood population. It is proposed that this facilitation may reflect a process that leads to binocularity and that develops rapidly with binocular alignment.