Polycoria

Polycoria is a pathological condition of the eye characterized by more than one pupillary opening in the iris.[1] It may be congenital or result from a disease affecting the iris.[1] It results in decreased function of iris and pupil, affecting the physical eye and visualization.

Epidemiology

Polycoria is extremely rare, and other conditions are frequently mistaken for it.[2][3] Polycoria is often congenital, however not diagnosed until adulthood.[4] The general cause of polycoria is unknown, but there are some other eye conditions that are in association with polycoria. These include (although not often) polar cataracts, glaucoma, abnormally long eyelashes, abnormal eye development, and poor vision.

There have been cases diagnosed from age 3 to adulthood. The prevalence of true polycoria is minimal.[3] The two kinds of polycoria are true polycoria and false pseudopolycoria.

There are no known or proposed trends in the occurrences of polycoria based on geographical location, age, gender, or season.

True polycoria

In cases of true polycoria, there is an extra pupil that tends to be reactive to light and medication.[5] 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.[6] The extraneous pupil is c. 2.5mm away from the principal pupil. In cases of true polycoria there is an intact sphincter muscle, which contracts and dilates the pupils.[5] In an eye without polycoria, the sphincter muscle is a part of the iris that functions to constrict and dilate the pupil.[7] A patient with true polycoria experiences handicapped vision as well as stimulation of the retina in response to bright lights.[5]

It is said that the term "true polycoria" is overused, and used correctly when addressing congenital deformations of the iris.[6] 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.[5]

Pseudopolycoria consists of splitting of the iris that are not contingent with the sphincter muscles at the root of the iris.[6]

Symptoms and diagnosis

When a patient is diagnosed with polycoria, the signs and symptoms shown are associated with ocular and adnexal growth abnormalities.[8] 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.[9]

Upon gross examination the patient will typically have excessively long eyelashes.[8] The iris becomes hypoplastic, making abnormally shaped pupils with prominent crypts.[8] The crypts are little squiggly lines that radiate out around the pupil; with this condition, thick round or oval openings can be seen.[8]

On diagnosis, signs lead to symptoms where there is more than one set of iris muscles, which controls the amount of light being brought into the eye.[8] When the iris becomes deformed, it will disarrange the control of light coming in leading to blurred vision and finding it hard to visually focus. Polar cataracts will also be present in this condition where a round, opaque malformation of distorted lens fibers is located in the central posterior part of the lens showing disformality.[10] Blindess may also be caused due to damage of the optic nerve from glaucoma.[9]

Treatment

Polycoria has been linked to hereditary genetics,[8] and also associated with polar cataracts, glaucoma, and retinal detachment.[5] Not all cases are treated for this iris abnormality, but when cases are treated the only treatment is surgical procedure and life-long ocular monitoring that is highly recommended.[11] Considerations for surgery are surgical correction, intraocular surgery, and/or reapproximation, as if it was being treated for glaucoma or retinal detachment.[11] Children under the age of 3, who do not seek surgical surgery, have responded well with miotic drops that contained mydriatic/cycloplegic, allowing the separate eye sphincters to dilate and constrict together. This allows improved balance of uncorrected visual acuity.[12] A 1-mm limbal incisions would be made, a spatula is inserted through the side to elevate the two pupils (avoiding contact with the lens), and the iris tissue would be cut using viscoelastic material. Finally, the limbal incisions were closed with stromal hydration, and intracameral cefuroxime is applied.[5]

Surgical technique

There have been cases where there are various techniques for surgical procedures[12] and can be performed on children and adults. One of the techniques for repair is by using a double armed polypropylene suture, where the suture is left externally on the sclera with a knot buried in the scleral flap.[13] This technique allows posterior fixation of intraocular lens implants in the absence of capsular support.[14] Another technique for surgery is called pupilloplasty,[15] where the patient would be placed under retrobulbar anesthesia with the pupils being dilated with 1% tropicamide.[5]

Prognosis

Postoperative care

Hypertonic saline solution used as eye drops may be used to reduce the corneal edema,[16] the use of anti-glaucomatous topicals to help improve corneal edema, and aqueous suppressants that are accompanied by miotics, include topical beta blockers, alpha antagonists, and carbonic anhydrase inhibitors.[17] Antibiotics and steroid drops for 4 weeks post surgery.[5]

Complications and benefits

Complications of surgical procedures are possible suture erosion through the sclera, conjunctiva, or both.[14] Minor intraocular inflammation during and after surgery.[5] Improved distant and near visual acuity, little defects surrounding sphincter muscles, and normal pupillary margins.[8]

Prevention

There are no known preventive measures for polycoria, however genetic testing may be able to reveal genetic patterns of the disorder. 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).[18] 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.[5]

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.[6] Polycoria can also be caused any hole in one's iris to develop a sphincter muscle development.[6] Another proposed theory about the cause of polycoria is intra-uterine trauma, or postpartum iris trauma.[6]

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.[6]

Genetics

The gene that is the cause of this disorder is the PRDM5 gene.[11] The PRDM5 gene has also been linked to Brittle Cornea syndrome, which is a tissue disorder of the eye, as well as Axenfeld syndome.[11] PRDM5 plays crucial roles in the molecular composition of the eye, as well as the tissue thickness.[11] Axenfeld syndrome occurs in the patient in a case of the mutation of the FOXC1 gene, which is a heterozygous mutation.[11]

History

Since true polycoria and pseudopolycoria are so rare, there is not much history on the disorders. According to an article published in 2002, there have only been 2 cases of true polycoria since 1966.[3]

See also

• Eye injury
• Iridodialysis
• Monocular diplopia
• Coloboma

References

1. Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainesville, Florida: Triad Publishing Company, 1990.
2. Islam, N.; Mehta, J. S.; Plant, G. T. (2007). "True polycoria or pseudo-polycoria?". Acta Ophthalmologica Scandinavica. 85 (7): 805–806. doi:10.1111/j.1600-0420.2007.00985.x. PMID 17711542.
3. Hofeldt, Gregory T.; Simon, John W. (2002-10-01). "Polycoria, miosis, and amblyopia". Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS}. 6 (5): 328–329. doi:10.1067/mpa.2002.124649. ISSN 1091-8531. PMID 12381993.
4. Berradi, Soufiane; Lezrek, Mounir (2014-09-30). "Pseudo-hypopion inverse avec polycorie congénitale". The Pan African Medical Journal. 19: 108. doi:10.11604/pamj.2014.19.108.3960. ISSN 1937-8688. PMC 4337356. PMID 25722781.
5. Bardak, Handan; Ercalik, Nimet Yesim; Gunay, Murat; Bolac, Ruveyde; Bardak, Yavuz; Bardak, Handan; Ercalik, Nimet Yesim; Gunay, Murat; Bolac, Ruveyde; Bardak, Yavuz (December 2016). "Pupilloplasty in a patient with true polycoria: a case report". Arquivos Brasileiros de Oftalmologia. 79 (6): 404–406. doi:10.5935/0004-2749.20160114. ISSN 0004-2749. PMID 28076571.
6. Jaffe, Norman S.; Knie, Paul (1952-02-01). "True Polycoria*". American Journal of Ophthalmology. 35 (2): 253–255. doi:10.1016/0002-9394(52)90856-8. ISSN 0002-9394. PMID 14903014.
7. "Iris sphincter muscle", Wikipedia, 2019-11-19, retrieved 2019-11-22
8. Bhattacharjee, Harsha; Bhattacharjee, Kasturi; Tahiliani, Prerana (2013-12-01). "Congenital polycoria, trichomegaly, and hereditary congenital cataract". Journal of American Association for Pediatric Ophthalmology and Strabismus. 17 (6): 619–620. doi:10.1016/j.jaapos.2013.06.020. ISSN 1091-8531. PMID 24321426.
9. "Polycoria: Causes, Symptoms, and Treatments". Healthline. Retrieved 2019-11-22.
10. "Posterior Polar Cataract: Background, History of the Procedure, Problem". 2019-11-09. Cite journal requires |journal= (help)
11. "polycoria | Hereditary Ocular Diseases". disorders.eyes.arizona.edu. Retrieved 2019-11-22.
12. Hofeldt, Gregory T.; Simon, John W. (2002-10-01). "Polycoria, miosis, and amblyopia". Journal of American Association for Pediatric Ophthalmology and Strabismus. 6 (5): 328–329. doi:10.1067/mpa.2002.124649. ISSN 1091-8531. PMID 12381993.
13. Inoue, Toshihiro; Matsumura, Riyo; Kuroda, Utako; Nakashima, Kei-Ichi; Kawaji, Takahiro; Tanihara, Hidenobu (December 1, 2012). "Precise Identification of Filtration Openings on the Scleral Flap by Three-Dimensional Anterior Segment Optical Coherence Tomography". Investigative Ophthalmology & Visual Science. 53 (13): 8288–8294. doi:10.1167/iovs.12-10941. PMID 23188727.
14. Brown, Sandra M. (1998-12-01). "A technique for repair of iridodialysis in children". Journal of American Association for Pediatric Ophthalmology and Strabismus. 2 (6): 380–382. doi:10.1016/S1091-8531(98)90041-6. ISSN 1091-8531. PMID 10532731.
15. "Pupilloplasty – Webvision".
16. "Corneal Edema – Products for temporary daytime and nighttime relief when you suffer from Corneal Edema : Bausch + Lomb". www.bausch.com.
17. Sacchetti, Marta; Mantelli, Flavio; Marenco, Marco; Macchi, Ilaria; Ambrosio, Oriella; Rama, Paolo (2015). "Diagnosis and Management of Iridocorneal Endothelial Syndrome". BioMed Research International. 2015: 763093. doi:10.1155/2015/763093. ISSN 2314-6133. PMC 4588350. PMID 26451377.
18. Mohammadpour, Mehrdad; Heidari, Zahra; Hashemi, Hassan (2017-12-06). "Updates on Managements for Keratoconus". Journal of Current Ophthalmology. 30 (2): 110–124. doi:10.1016/j.joco.2017.11.002. ISSN 2452-2325. PMC 6034171. PMID 29988906.