Pupula Duplex Anomaly

Pupula duplex anomaly, also known as polycoria, is a condition of the eye characterized by more than one pupillary opening in the iris. It may be congenital or result from a disease affecting the iris. It results in decreased function of iris and pupil, affecting the physical eye and visualization.

In the early history of China, double pupils were seen as a sign that a child would become a great king or sage.

Pupula duplex anomaly is extremely rare. It is often congenital, however not diagnosed until adulthood. The general cause of pupula duplex anomaly is unknown, but there are some other eye conditions that are in association with pupula duplex anomaly. These include (although not often) polar cataracts, glaucoma, abnormally long eyelashes, abnormal eye development, and poor vision.

There have been cases diagnosed from age three to adulthood. The prevalence of true pupula duplex anomaly is minimal. The two kinds of pupula duplex anomaly are true polycoria and false or pseudopolycoria[1].

In cases of true polycoria, there is an extra pupil that tends to be reactive to light and medication.To be considered true polycoria the extra pupil and the principal pupil must dilate and contract simultaneously with triggers such as light and administered drugs. The extraneous pupil is circa 2.5 millimeters away from the principal pupil. In cases of true polycoria there is an intact sphincter muscle, which contracts and dilates the pupils. In an eye without polycoria, the sphincter muscle is a part of the iris that functions to constrict and dilate the pupil. A patient with true polycoria experiences handicapped vision as well as stimulation of the retina in response to bright lights.

Although less rare than true polycoria, pseudopolycoria is still very uncommon. In cases of pseudopolycoria there is a 'passive constriction' that differentiates the extra pupil from the true pupil during constriction and dilation. The extra pupil in pseudopolycoria is different than the extra pupil in true polycoria because it shows defects that are independent of the sphincter muscles. Pseudopolycoria is often associated with Seckel syndrome, posterior polymorphous dystrophy, and juvenile glaucoma. Pseudopolycoria consists of splitting of the iris that are not contingent with the sphincter muscles at the root of the iris.

But pupula duplex anomaly is often misdiagnosed. For instance, people with Axenfeld-Rieger syndrome often have a pupil that is off-center (corectopia) or extra holes in the iris that can look like multiple pupils [2].

[1] Islam et al: True polycoria or pseudo-polycoria? in Acta Ophthalmologica Scandinavica - 2007
[2] Zamora and Salini: Axenfeld-Rieger Syndrome - 2022