Normal distribution of palpebral fissure lengths in Canadian school age children.

BACKGROUND Fetal alcohol syndrome (FAS) includes the facial dysmorphic feature of short palpebral fissures (PFs) and short PFs are a key physical marker for identifying children with FAS and some other rarer conditions. There is concern that normative data on PFs now available may not reflect all racial/ethnic groups and might be inaccurate in general. OBJECTIVES To accomplish a large population based study that would accurately determine normative PF values across the full diversity of the Canadian school age population. METHODS A normative sample of school age children was identified in Vancouver, British Columbia and Winnipeg, Manitoba to reflect the diversity of racial and national groups in Canada. The sample included students in grades 2, 4, 6, 8, and 10 from 17 schools in Vancouver and 31 schools in Winnipeg. Schools were selected based on racial diversity obtained from data from the 2001 Statistics Canada census. 1064 students in Vancouver and 1033 students in Winnipeg were photographed in a standardized way. Photographs were analyzed using a computerized method. RESULTS Analysis demonstrated that PFs do grow with age and there is a slight but meaningful difference between boys and girls in each age group. It is possible to define Canadian standards without reference to racial or ethnic origin. CONCLUSION Mean results with norms and standard deviations are presented in figures for clinical use and are clinically smaller than those found in the most commonly used reference book.