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Co-development of VEP motion response and binocular vision in normal infants and infantile esotropes
E E Birch1, S Fawcett, D Stager
1Retina Foundation SW, Dallas, Texas 75231, USA. ebirch@retinafoundation.org
Insights
Infantile esotropia involves abnormal visual pathways, not just a developmental delay. Fusion and motion visual evoked potential (MVEP) symmetry are strongly linked in developing vision.
Area of Science:
- Neuroscience
- Ophthalmology
- Developmental Biology
Background:
- Infantile esotropia is a common condition affecting eye alignment in infants.
- Understanding the developmental trajectory of visual processing is crucial for early diagnosis and intervention.
Purpose of the Study:
- To investigate the maturation of nasotemporal asymmetry in infantile esotropia.
- To examine the relationship between motion visual evoked potential (MVEP) symmetry, eye alignment, fusion, and stereopsis.
Main Methods:
- Assessed nasotemporal MVEP asymmetry using interocular phase difference and amplitude asymmetry index.
- Evaluated fusion with prism tests and stereoacuity using preferential looking.
- Measured eye alignment with cover and Krimsky tests in healthy infants and those with esotropia.
Main Results:
- Normal infants showed MVEP asymmetry that decreased with age, while neonates lacked it.
- Good concordance was found between MVEP symmetry, fusion, and stereopsis.
- MVEP symmetry showed poorer concordance with visual axis alignment; most infantile esotropia patients had asymmetrical MVEPs post-surgery.
Conclusions:
- A strong association exists between fusion and MVEP symmetry during normal visual maturation and in infantile esotropia.
- Asymmetry in older esotropic infants suggests a pathological change in motion pathways rather than a maturational arrest.
Purpose:
To determine the maturational course of nasotemporal asymmetry in infantile esotropia and to define the relationships among the symmetry of the motion visual evoked potential (MVEP), eye alignment, fusion, and stereopsis.
Methods:
Sixty healthy term infants and 34 infants with esotropia participated. Nasotemporal MVEP asymmetry was assessed by the presence of a significant F1 response component with an interocular phase difference of approximately 180 degrees and by an amplitude "asymmetry index." Fusion was evaluated using the 4 p.d. base out prism test. Random dot stereoacuity was assessed in infants with forced-choice preferential looking (FPL) using the Infant Random Dot Stereocards. Eye alignment was assessed by the alternate prism and cover or the modified Krimsky test.
Results:
Normal infants 2 to 3 months of age exhibited marked nasotemporal MVEP asymmetry, which rapidly diminished by 6 to 8 months. Neonates did not exhibit MVEP asymmetry. There was good concordance between fusion and MVEP symmetry and between stereopsis and MVEP symmetry; the concordance between MVEP symmetry and orthoposition of the visual axes was significantly poorer. The same proportion of normal and young esotropic infants showed symmetrical MVEPs. Regardless of the age at surgery, most patients with infantile esotropia had asymmetrical MVEPs after surgery.
Conclusions:
These data support a strong link between fusion and MVEP symmetry during both normal maturation and in infantile esotropia. Furthermore, the finding that the youngest infants with esotropia do not differ significantly from normal suggests that the nasotemporal asymmetry found in older patients with infantile esotropia does not represent an arrest of maturation but, rather, a pathologic change of the motion pathways.