Dysmorphology and the orbital region: a practical clinical approach.

Dysmorphology is the field of medicine focusing on congenital developmental abnormalities due to exogenous teratogens, chromosomal anomalies, or to a defect in a single gene. Numerous syndromes have been reported and a growing number of genes or chromosomal anomalies are identified. The clinical observation of the face remains an essential part of the clinical evaluation of the patients. The orbital region, as other regions of the face, should be systematically evaluated. Orbital malformations can be isolated or part of a syndrome. In the diagnostic process, the orbital anomaly can be classified as a major feature (essential for the diagnosis), a moderate feature (important but not essential for the diagnosis), or a minor feature (contributing weakly to the diagnosis). The diagnoses of the main orbital anomalies in dysmorphology are reviewed and illustrated with relevant examples of syndromes that are presented as well as the usual landmarks used in clinical practice. Abnormal position of the eyes in syndromes such as hypertelorism, hypotelorism, primary or secondary telecanthus, asymmetry, and proptosis are discussed. Eyelid anomalies, such as cryptophthalmos, ablepharon, blepharophimosis, euryblepharon, or anomalies at the level of the eyelashes and eyebrows are described.