Polycoria is a pathological condition of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

Distinguished by more than one pupillary opening in the iris.Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company, 1990. It may be congenital or result from a disease affecting the iris. It results in decreased function of the 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.

Epidemiology

Polycoria is extremely rare, and other conditions are frequently mistaken for it. Polycoria is often congenital, however not diagnosed until adulthood. 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. The two kinds of polycoria are true polycoria and 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 The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company. It appears black becau ...

that tends to be reactive to light and medication. To be considered true polycoria, the extra pupil and the principal pupil must

dilate Dilation (or dilatation) may refer to: Physiology or medicine * Cervical dilation, the widening of the cervix in childbirth, miscarriage etc. * Coronary dilation, or coronary reflex * Dilation and curettage, the opening of the cervix and surg ...

, and contract simultaneously with triggers such as light, and administered drugs. The extraneous pupil is c. 2.5mm away from the principal pupil. In cases of true polycoria, there is an intact

sphincter muscle A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the human bo ...

, 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 The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

in response to bright lights. It is said that the term "true polycoria" is overused, and used correctly when addressing

congenital A birth defect is an abnormal condition that is present at childbirth, birth, regardless of its cause. Birth defects may result in disability, disabilities that may be physical disability, physical, intellectual disability, intellectual, or dev ...

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

The signs and symptoms shown in a patient diagnosed with polycoria 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 Gross processing, "grossing" or "gross pathology" is the process by which pathology specimens undergo examination with the bare eye to obtain diagnosis, diagnostic information, as well as cutting and tissue sampling in order to prepare material fo ...

the patient will typically have excessively long eyelashes. The iris becomes

hypoplastic Hypoplasia (; adjective form ''hypoplastic'') is underdevelopment or incomplete development of a Tissue (biology), tissue or Organ (biology), organ.crypts. The crypts are little squiggly lines that radiate out around the pupil; with this condition, thick round or oval openings can be seen. 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. 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

cataract A cataract is a cloudy area in the lens (anatomy), lens of the eye that leads to a visual impairment, decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or ...

s 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.

Treatment

Polycoria has been linked to hereditary genetics, and also associated with polar cataracts, glaucoma, and retinal detachment. 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. Considerations for surgery are surgical correction, intraocular surgery, and/or reapproximation, as if it was being treated for glaucoma or retinal detachment. Children under the age of 3, who do not seek 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. 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.

Surgical technique

There have been cases where there are various techniques for surgical procedures 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. This technique allows posterior fixation of intraocular lens implants in the absence of capsular support. Another technique for surgery is called pupilloplasty, where the patient would be placed under retrobulbar anesthesia with the pupils being dilated with 1% tropicamide.

Prognosis

Postoperative care

Hypertonic saline solution used as eye drops may be used to reduce the corneal edema, 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. Antibiotics and steroid drops for 4 weeks post surgery.

Complications and benefits

Complications of surgical procedures are: * Possible suture erosion through the

sclera The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective outer layer of the eye containing mainly collagen and some crucial elastic fiber. In the development of t ...

conjunctiva In the anatomy of the eye, the conjunctiva (: conjunctivae) is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with gobl ...

, or both. * Minor intraocular inflammation during and after surgery. * Improved distant and near visual acuity, little defects surrounding sphincter muscles, and normal pupillary margins.

Prevention

There are no known preventive measures for polycoria, however

genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...

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 an eye disorder in which the cornea, the transparent front part of the eye, gradually thins and bulges outward into a cone shape. This causes distorted vision, including blurry vision, double vision, increased nearsightedness, ...

(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 are 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 one's 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 The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the o ...

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.

History

Since true polycoria and pseudopolycoria are so rare, there is not much history on the disorders in the tradition of modern western medicine. According to an article published in 2002, there have only been 2 cases of true polycoria since 1966. Early Chinese history names multiple legendary figures as having double pupils, which as a result led to a belief that a child born with two double pupils was destined to be a great king or sage.

Xiang Yu Xiang Yu (), born Xiang Ji, was a Chinese warlord who founded and led the short-lived ancient Chinese states, kingdom-state of Western Chu during the interregnum period between the Qin dynasty, Qin and Han dynasty, Han dynasties of China, d ...

, Hegemon of Chu, blood brother and later arch nemesis of

Liu Bang Emperor Gaozu of Han (2561 June 195 BC), also known by his given name Liu Bang, was the founder and first emperor of the Han dynasty, reigning from 202 to 195 BC. He is considered by traditional Chinese historiography to be one o ...

, the founding emperor of the

Han dynasty The Han dynasty was an Dynasties of China, imperial dynasty of China (202 BC9 AD, 25–220 AD) established by Liu Bang and ruled by the House of Liu. The dynasty was preceded by the short-lived Qin dynasty (221–206 BC ...

, was given great esteem due to his prowess in combat and auspicious double pupil. After overthrowing the

Qin dynasty The Qin dynasty ( ) was the first Dynasties of China, imperial dynasty of China. It is named for its progenitor state of Qin, a fief of the confederal Zhou dynasty (256 BC). Beginning in 230 BC, the Qin under King Ying Zheng enga ...

together, he was named Hegemon of the loose series of kingdoms he created in its wake, while he gave Liu Bang the remote province of Han. The Civil War that followed called the Chu-Han contention, ending with a Han victory and a legendary last stand by the Hegemon.

Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...

describes a mythological race of people known as Bythiæ who "have a double pupil in one eye, and in the other the figure of a horse." Plinius, ''

Naturalis Historia The ''Natural History'' () is a Latin work by Pliny the Elder. The largest single work to have survived from the Roman Empire to the modern day, the ''Natural History'' compiles information gleaned from other ancient authors. Despite the work' ...

''7, 11.

References

{{Reflist Congenital disorders of eyes