Epicanthal folds can be congenital or acquired. Congenital epicanthal folds can be observed in young children of all races as a normal finding before the nasal bridge elevates, or it can be seen as a normal racial variation, particularly in East Asians, Eskimos, Native Americans, and some Southern African tribes, where it usually persists with no attenuation.² In a recent study that surveyed the normative periocular anthropometric values in children versus young adults from the Chinese Han population, the authors demonstrated that with advancing age, epicanthal folds do tend to regress and are less frequently observed in young adults.⁵ Several syndromes are also associated with epicanthal folds, such as the blepharophimosis syndrome (see Chapter 28) or Down syndrome.

Acquired causes include penetrating injury or burn trauma to the medial canthal region. An iatrogenic epicanthal fold or cicatricial canthal web may also occur during aggressive excision of grade II or III xanthelasma if the surgeon bridges the medial canthal region with the same incision and may also occur due to an abnormally curved or unusually high dacryocystorhinostomy incision. In these patients, severe webbing of the medial canthal region may result in vertical skin contracture and a hypertrophic semilunar skin fold that closely resembles an epicanthal fold.⁵,⁷,⁸,⁹ Acquired cicatricial webbing may also occur laterally at the lateral canthal region following trauma or an aggressive combined upper and lower eyelid blepharoplasty.⁸,¹⁰,¹¹

The main underlying topographic abnormality in acquired cicatricial webs, and to a lesser extent in congenital epicanthal folds, is a localized vertical deficiency of the skin with a concomitant relative horizontal skin excess.⁸ In patients with congenital folds, it is important to remember that the vertical skin shortening is not the sole etiopathogenetic mechanism causing an epicanthal fold, as these congenital folds are also associated with an abnormal oblique redistribution of the preseptal orbicularis, the direction of which coincides with the direction of the epicanthal fold like the underlying events in epiblepharon.¹²,¹³ This abnormal preseptal orbicularis extends further downward to connect with its preseptal counterpart in the lower eyelid inside the epicanthal fold, a unique finding that is not observed in the normal population.¹⁴ The pretarsal portion of the orbicularis is not involved.¹⁴ Histopathologically, an epicanthal fold is therefore composed of three compartments: an outer skin lining, a fibromuscular core structure (preseptal orbicularis and fibrotic tissue), and an inner skin lining.¹⁴

Epicanthus is characterized by an extra fold of skin in the medial canthal area that can obscure a portion of the medial canthus and the lacrimal caruncle (Figure 31.1).⁶ The condition usually affects about 20% to 30% of the general occidental population at birth, but as the bridge of the nose elevates, it usually starts to get attenuated and mostly disappears around puberty; however, it may persist in some form or another in 2% to 5% of the population.¹,²,³,⁴ It is
important to realize that epicanthal folds are a normal finding in 40% to 90% of Asians where the normal appearance is hallmarked by an epicanthal fold that covers the medial part of the eyelids giving the illusion of telecanthus and horizontal phimosis, whereas in non-Asian races a normal appearance is defined by a rounded medial canthal angle coupled with total visualization of the caruncle and plica semilunaris.¹²,¹⁴,¹⁵