Primary entropion is an uncommon congenital anomaly. It is much rarer than the secondary type of congenital entropion, which is usually associated with anophthalmos, microphthalmos, epiblepharon, etc. In these secondary cases the cause is usually mechanical and is due either to (1) lack of support to the lid margin by a small or absent globe or (2) backward pressure on the ciliary margin by an excess fold of skin, as in epiblepharon. By definition, then, primary congenital entropion is usually seen in eyes with otherwise normal globes and adnexa.
The importance of this anomaly is in the injury which might be caused to the cornea by the inversion of the margin and lashes. The treatment is always surgical.
A total of 22 cases * of primary congenital entropion has been found in the literature to date. The statistics of these cases are interesting, though not particularly enlightening: Approximately two-thirds of the
FOX SA. Primary Congenital Entropion. AMA Arch Ophthalmol. 1956;56(6):839-842. doi:10.1001/archopht.1956.00930040851006