Anatomy of the Epicanthal Fold

Sir:FigureThe cause of epicanthal folds is multifocal.1,2 A Z-shaped kinking of orbicularis muscle fibers, an excess of underlying orbicularis muscle and fibroadipose tissue, and no or little attachment of the medial levator aponeurosis have been thought to be causative factors.1,2 However, no detailed anatomy of the epicanthal folds has been disclosed so far, although surgery for epicanthal folds is a main concern of cosmetic surgery.2–5 We therefore examined the anatomy of the epicanthal folds. Microscopic examination was used to study the relationship among the epicanthal folds, the orbicularis muscle, and the levator aponeurosis. Ten postmortem eyelids with an epicanthal fold were harvested from seven Japanese cadavers aged 61 to 83 years at death (average, 73.0 years). The exenterated specimens were incised axially at 3 mm superior to the upper eyelid margin. The histologic specimens were sectioned with 7-μm thickness and stained with Masson trichrome. Macroscopic examination, using six specimens from four Japanese cadavers aged 74 to 88 years at death (average, 80.8 years), was used to study the relationship between the epicanthal fold skin and the orbicularis muscle and the relationship between the orbicularis muscle and the medial levator aponeurosis. All cadavers were registered in Aichi Medical University. Proper consent and approval were obtained before their use. Methods for securing human tissues were humane and complied with the tenets of the Declaration of Helsinki. None of the cadavers had any history or clinical evidence of a previous trauma, surgery, or any other abnormality in the periocular region. All epicanthal folds examined were the epicanthus tarsalis. Microscopically, the intermuscular fibers of the preseptal orbicularis muscle (muscle with small fasciculi) extended anteriorly to reach the skin (Fig. 1), and those of the pretarsal orbicularis muscle (muscle with large fasciculi) went from the posterior lacrimal crest and extended laterally. The levator aponeurosis did not extend its fibers to the medial canthal skin area.Fig. 1: Microscopic specimen. OM, orbicularis muscle.Macroscopically, subcutaneous tissue with rich fibroadipose tissue was situated between the skin and the orbicularis muscle. The orbicularis muscle did not show a Z-shaped kinking or hypertrophy (Fig. 2). The preseptal orbicularis fasciculi ran obliquely around the epicanthal fold area (Fig. 2) and coincided with the direction of the epicanthal folds. The medial levator aponeurosis was always situated in the orbital side against the orbicularis muscle.Fig. 2: Macroscopic specimen.We disclosed the anatomical etiologic factors of the epicanthal folds, although all specimens were the epicanthus tarsalis. The epicanthal fold formation depended on the intermuscular fibers of the oblique direction preseptal orbicularis muscle. The fasciculi direction of the oblique preseptal orbicularis muscle coincided with the direction of the epicanthal folds. The epicanthus tarsalis, epicanthus supraciliaris, and epicanthus palpebralis, which are thought to be on the same anatomical line,2,3 may be differentiated on the basis of which part of the oblique direction preseptal orbicularis muscle affects most. From this standpoint, a case without the epicanthal fold may be under the influence of the pretarsal orbicularis muscle. An epicanthal fold revision is described, therefore, to change the influence under the preseptal orbicularis muscle to that of the pretarsal orbicularis muscle. Hirohiko Kakizaki, M.D., Ph.D. Department of Ophthalmology, Aichi Medical University, Nagakute, Aichi, Japan Akihiro Ichinose, M.D., Ph.D. Department of Plastic Surgery, Kobe University School of Medicine, Kobe, Hyogo, Japan Takashi Nakano, M.D., Ph.D. Ken Asamoto, M.D., Ph.D. Department of Anatomy Hiroshi Ikeda, M.D., Ph.D. Department of Pathology, Aichi Medical University, Nagakute, Aichi, Japan DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.