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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 the iris and pupil, affecting the physical eye and visualization.
The most common cause of POS is cat-scratch disease, an infectious disease that typically results from a scratch or bite from a cat. However, this syndrome is an unusual feature of cat-scratch disease. In rare cases, other infections may also cause the syndrome. [1] Bartonella henselae [2] Francisella tularensis [3] Herpes simplex virus type 1 [4]
The most common symptom is decreased visual acuity in one eye. The diagnosis is made by examination of the eye, using ophthalmoscopy. Sometimes serologic testing is used to rule out the disease, but due to high rates of false positives, serologies are not diagnostic of toxoplasmic retinitis.
A mydriatic pupil will remain excessively large even in a bright environment. The excitation of the radial fibres of the iris which increases the pupillary aperture is referred to as a mydriasis. More generally, mydriasis also refers to the natural dilation of pupils, for instance in low light conditions or under sympathetic stimulation.
Leukocoria (also white pupillary reflex) is an abnormal white reflection from the retina of the eye. Leukocoria resembles eyeshine, but leukocoria can also occur in animals that lack eyeshine because their retina lacks a tapetum lucidum.
When the test is performed in an eye with an afferent pupillary defect, light directed in the affected eye will cause only mild constriction of both pupils (due to decreased response to light from the afferent defect), while light in the unaffected eye will cause a normal constriction of both pupils (due to an intact efferent path, and an ...
The tonic pupil may become smaller (miotic) over time which is referred to as "little old Adie's". [5] Testing with low dose (1/8%) pilocarpine may constrict the tonic pupil due to cholinergic denervation supersensitivity. [1] A normal pupil will not constrict with the dilute dose of pilocarpine. [5]
Progressive retinal atrophy (PRA) is a group of genetic diseases seen in certain breeds of dogs and, more rarely, cats. Similar to retinitis pigmentosa in humans, [1] it is characterized by the bilateral degeneration of the retina, causing progressive vision loss culminating in blindness.