Recruitment of Suitable Families to Identify Causative Genes in Hereditary Strabismus

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The cause and origin of primary strabismus are not well understood. It is thought that there is multifactorial genetic inheritance. Only linkage analysis has been applied to study the genetic causes and correlations. The objective of this study was the compilation and statistical evaluation of a useful cohort of families for linkage analysis. The archives of the Department of Ophthalmology of the Justus-Liebig-University Gießen were used as a database for this study. Medical records of visits between January 2001 and July 2008 were analysed. Evaluation was based on the medical history form. The data set was scanned for index families in which at least two members had any form of primary strabismus. Patients were classified according to their type of primary strabismus. Families who were most suitable for linkage analysis were approached. A disease specific questionnaire was developed to complete the data. Between January 2001 and July 2008, 20,813 patients affected by primary strabismus were treated. The data set contained 2380 patients with a positive family history of primary strabismus. The majority presented with esotropia (67 %), followed by exotropia (21 %). In most cases (80 %), two family members were affected and the child-parent relationship contributed the largest group, including 948 cases (40 %). Affected siblings were found in 397 families (17 %). Three affected patients were identified in 432 (18 %) families. In these, the relationship parent-child-sibling occurred most frequently, with 143 cases (6 %). A positive family history of at least four related patients was found in 46 families (2 %). Forty-two families were particularly suitable for linkage analysis. Seventeen of the 42 families answered a questionnaire aimed at improving the data set. Three families finally participated in ophthalmic examinations and agreed to blood sampling to perform linkage analysis. The fraction of families with strabismus patients in more than two consecutive generations was extremely low. If these families are included in any study, this should be coupled to treatment to improve compliance.