The medial canthus can be classified into four main types type I to type IV (see pictures below) depending on the amount and type of epicanthal fold present. Amongst the East Asians, type II and type III are the most common (with type II being more common than type III in adult East Asians) accounting for more than 90% of cases, type I is present in less than 10% of East Asians. Type IV is rare and is usually a pathological condition seen in congential anomaly such as blepharophimosis.
Type I: Full exposure of the lacrimal caruncle (in red). There is no epicanthal fold in this type. This is seen in most Caucasian people.
Type II: The lacrimal caruncle is partially covered, the epicanthal fold joins the skin at the margin of the lacrimal lake. This is the most common type amongst adult East Asians.
Type III: The lacrimal caruncle is covered almost completely, the fold in the lower eyelid curves laterally to blend in with the lower eyelid skin. The medial palpebral fissure appears round. This type of epicanthal fold is most commonly seen in young East Asians but as the nasal bridge grows, the epicanthal fold gets pulled progressively to the centre to become type II epicanthal fold.
Type IV: This is rare and is a reversed epicanthal fold. The fold originates from the lower eyelid and blends with the upper eyelid skin, this type of epicanthal fold is the most severe and make the eye looks exceedingly small.
Using the classification above, you may like to try classifying the epicanthal folds in the following faces (answers at the bottom)
a. Type II without double eyelids
b. Type IV a patient with blepharophimosis, note the small eyes and droopy eyelids.
c. Type I with double eyelids.
d. Type II with double eyelids.
e. Type III in a young girl.
f. Type II without double eyelid.