Inheritance of strabismus and the gain of using heredity to determine populations at risk of developing strabismus

Purpose: In the Nordic countries 2 to 4% of the population squint or have b een squinting. Since strabismus is one of the major causes of amblyopia ear ly detection and treatment is important for preventing this development. Eb r centuries it has been recognized that strabismus is hereditary. Identifyi ng individuals with a family history of squinting could give access to a ri sk population for a selective screening. Methods and results: 1571 children were selected for this study. All childr en that took part in a voluntary eye examination at one year of age (born 1 978-1983) in the city of Vasteras, Sweden and that had a family history of strabismus were selected together with controls. The study was a B-year fol low-up from 1 to 7 years of age. Parental knowledge of squint among relativ es and measured high hyperopia (>3.0 D) present at 1 year of age were each and in combination evaluated as a risk indicator for development of strabis mus between 1 to 7 years of age. Conclusion: The study indicates that a family history of squint in combinat ion with measured high hyperopia can be used in a selective screening to id entify a population with an increased risk of 4 to 6 times for developing s trabismus. Among the children with parental knowledge of squint among sever al relatives of both the parents, those with high hyperopia developed strab ismus in almost every second case while this was the case in only approxima tely 10% of those with low hyperopia. Finally, heredity is an important ris k indicator that can be used for selective screening purpose. Its potential as a risk indicator is substantially increased when combined with st high hyperopia.