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Can misalignments in typical infants be used as a model for infantile esotropia?
Anna M Horwood1, Patricia M Riddell
1School of Psychology, University of Reading, Reading, United Kingdom.
Insights
Early ocular misalignments in infants are not linked to accommodation but are more common without retinal disparity cues and when targets move away. This suggests strabismus may stem from impaired motion-direction sensitivity.
Area of Science:
- Ophthalmology
- Developmental Biology
- Pediatrics
Background:
- Early ocular misalignments in infants are a significant concern for visual development.
- Understanding the etiology of conditions like esotropia is crucial for timely intervention.
Purpose of the Study:
- To investigate early ocular misalignments in infants.
- To explore potential links between misalignments and the etiology of esotropia.
- To identify correlates of infant ocular misalignments.
Main Methods:
- A remote haploscopic photorefraction system measured accommodation and vergence in 146 infants (0-12 months).
- Infants viewed a moving target at various distances, with tests conducted under binocular and monocular (occluded) conditions.
- Data were analyzed to assess associations between accommodative behavior, retinal disparity, and misalignment occurrence.
Main Results:
- No correlation was found between infant accommodative behavior and ocular misalignments.
- Misalignments were more prevalent when retinal disparity cues were absent (eye occlusion).
- Infants showed increased misalignments when a target moved from near to far, compared to far-to-near movement.
Conclusions:
- Retinal disparity cues reduce misalignment prevalence in 2-3 month old infants.
- Target movement away from the infant increases misalignment prevalence.
- Findings support theories linking strabismus to impaired sensitivity to motion direction.
Purpose:
To investigate the nature of early ocular misalignments in human infants to determine whether they can provide insight into the etiology of esotropia and, in particular, to examine the correlates of misalignments.
Methods:
A remote haploscopic photorefraction system was used to measure accommodation and vergence in 146 infants between 0 and 12 months of age. Infants underwent photorefraction immediately after watching a target moving between two of five viewing distances (25, 33, 50, 100, and 200 cm). In some instances, infants were tested in two conditions: both eyes open and one eye occluded. The resultant data were screened for instances of large misalignments. Data were assessed to determine whether accommodative, retinal disparity, or other cues were associated with the occurrence of misalignments.
Results:
The results showed that there was no correlation between accommodative behavior and misalignments. Infants were more likely to show misalignments when retinal disparity cues were removed through occlusion. They were also more likely to show misalignments immediately after the target moved from a near to a far position in comparison to far-to-near target movement.
Discussion:
The data suggest that the prevalence of misalignments in infants of 2 to 3 months of age is decreased by the addition of retinal disparity cues to the stimulus. In addition, target movement away from the infant increases the prevalence of misalignments. These data are compatible with the notion that misalignment are caused by poor sensitivity to targets moving away from the infant and support the theory that some forms of strabismus could be related to failure in a system that is sensitive to the direction of motion.