Canadian Palpebral Fissure Length Growth Charts Reflect a Good Fit for Two School and FASD Clinic-Based U.S. Populations
J Popul Ther Clin Pharmacol Vol 18(2):e231-e241; April 8, 2011
Original Research
Susan J Astley

Background
Short palpebral fissure lengths (PFL) are one of three facial features that define the unique facial phenotype of fetal alcohol syndrome (FAS). Published PFL growth charts vary greatly in both rate and magnitude of growth, placing their accuracy and validity in question. New PFL growth charts were recently published to reflect a racial/ethnic cross section of Canadian girls and boys 6-16 years of age. PFLs were measured from digital facial photographs using the FAS Facial Photographic Analysis Software.

Objectives
Assess the goodness of fit of two U.S. populations (healthy children and children with prenatal alcohol exposure) when plotted on the Canadian, Hall, and other published PFL charts.

Methods
The PFLs of 106 healthy children and 822 children with prenatal alcohol exposure from Washington State were measured from digital facial photographs using the FAS Facial Photographic Analysis Software. Goodness of fit was assessed graphically and by computation of the mean PFL z-score. 

Results
Our predominantly Caucasian, healthy group of children scattered along the mean growth curve on the Canadian charts (mean PFL z-score +0.2), and fell 1.6 SDs below the mean on the Hall chart (mean PFL z-score -1.6). The mean PFL z-score for the children with FAS was 2.4 SDs below the mean on the Canadian charts and 3.9 SDs below the mean on the Hall chart. African Americans were not a good fit. 

Conclusion
The Canadian PFL charts were a good fit for our predominantly Caucasian populations of healthy U.S. school-aged children. Children with FAS continued to present with PFLs 2 or more SDs below the mean when plotted on the Canadian PFL charts, supporting the FAS PFL diagnostic criteria used by the FASD 4-Digit Diagnostic Code. Use of PFL charts normed for African Americans is recommended. Updated PFL charts for 0-6 years of age are vital to prevent an artificial over-estimation of short PFLs in this age group. 

Key Words: Fetal alcohol syndrome (FAS); fetal alcohol spectrum disorders (FASD); FASD 4-Digit Diagnostic Code; palpebral fissure length

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