Conditions such as reduced corneal thickness, are observed in people with cases of polycoria, as well as keratoconus (keratoconus is a corneal disease has the possibility of leading to blindness and/or astigmatism). However, there are some proposals that it is caused by a dissociation of the pupil margins, a partial coloboma which is a hole in the eye, or abnormal eye tissue composition. Causes
There is not any known direct mechanisms involved in the development of true polycoria or pseudopolycoria. There are some proposed ideas, one being that after the sphincter muscle is fully formed and developed in the eye there is a severing of the pupillary margins leading to the distinction of the extra pupil and the principal pupil. Polycoria can also be caused any hole in ones iris to develop a sphincter muscle development. Another proposed theory about the cause of polycoria is intrauterine trauma, or postpartum iris trauma.If the development of the iris is hindered, the ectoderm of the eye (which forms the lens and corneal epithelium) may split, which could lead to pseudopolycoria. Genetics
The gene that is the cause of this disorder is the PRDM5 gene. The PRDM5 gene has also been linked to Brittle Cornea syndrome, which is a tissue disorder of the eye, as well as Axenfeld syndome. PRDM5 plays crucial roles in the molecular composition of the eye, as well as the tissue thickness. Axenfeld syndrome occurs in the patient in a case of the mutation of the FOXC1 gene, which is a heterozygous mutation.
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.It is said that the term "true polycoria" is overused, and used correctly when addressing congenital deformations of the iris. Often "true polycoria" is used when it in fact is a case of pseudopolycoria. Pseudopolycoria
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. Symptoms and diagnosis
When a patient is diagnosed with polycoria, the signs and symptoms shown are associated with ocular and adnexal growth abnormalities. The iris and the pupil become less effective. Signs can be present as a child; however, the patient may be diagnosed later in their life. This condition results in abnormal eye development affecting both eyes or just one.Upon gross examination the patient will typically have excessively long eyelashes. The iris becomes hypoplastic, making abnormally shaped pupils with prominent crypts.