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Associations between siblings for esotropia and exotropia
M J Podgor1, N A Remaley, E Chew
1Division of Biometry and Epidemiology, National Eye Institute, National Institutes of Health, Bethesda, Md, USA.
Insights
This study found a significant familial link for childhood strabismus, including esotropia and exotropia. Sibling and twin studies reveal genetic factors contribute to strabismus beyond known risks.
Area of Science:
- Ophthalmology
- Genetics
- Pediatrics
Background:
- Strabismus, a common childhood eye misalignment, has a suspected but not fully quantified familial component.
- Understanding familial aggregation is crucial for identifying genetic predispositions and developing targeted interventions.
Purpose of the Study:
- To quantify the familial aggregation of esotropia and exotropia in children.
- To investigate the role of genetic factors in the etiology of strabismus.
Main Methods:
- Utilized data from the Collaborative Perinatal Project, examining children up to age 7.
- Employed logistic regression with generalized estimating equations to assess familial aggregation of esotropia and exotropia.
- Analyzed sibling and multiple birth relationships, including zygosity, to determine associations.
Main Results:
- Esotropia showed a more than twofold increased odds in siblings when one sibling was affected.
- Exotropia demonstrated a significantly stronger association in siblings from multiple births (odds increased by at least 17-fold).
- Monozygotic twins exhibited a stronger association for both conditions than dizygotic twins, suggesting genetic influence.
Conclusions:
- A significant familial component contributes to the development of strabismus.
- Familial aggregation of strabismus is influenced by factors beyond currently identified risk factors.
- These findings underscore the importance of genetic counseling and early screening for families with a history of strabismus.
Objective:
To quantify familial aggregation of esotropia and exotropia in children examined in a large multicenter study.
Methods:
Pregnant women and their children were examined in the Collaborative Perinatal Project of the National Institute of Neurological Disorders and Stroke, Bethesda, Md. Strabismus was evaluated in the children during follow-up examinations up to the age of 7 years. The second-order generalized estimating equations approach to logistic regression was used to estimate familial aggregation of esotropia and exotropia.
Results:
For any pair of siblings, the odds for one sibling having esotropia more than doubled when the other sibling had esotropia. For exotropia, there were differences in sibling associations based on birth relationships. In particular, there was no statistically significant association between siblings from separate single births. On the other hand, for the pairs of siblings from multiple births (ie, twins, triplets, and quadruplets), the odds for exotropia in one sibling were increased by at least a factor of 17 when the other sibling from that birth also had exotropia. For both esotropia and exotropia, adjustment for previously identified risk factors only somewhat reduced the magnitudes of the observed associations. Limited data on zygosity showed a stronger association between monozygotic twins than between dizygotic twins.
Conclusions:
There is a significant familial component in the cause of strabismus. Furthermore, there are important contributions to this familial aggregation beyond those associated with known risk factors for strabismus.