Physiological anisocoria

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Physiological anisocoria is when human pupils differ in size. It is generally considered to be benign, though it must be distinguished from Congenital Horner's syndrome, pharmacological dilatation or other conditions connected to the sympathetic nervous system. [1] The prevalence of physiological anisocoria has not been found to be influenced by the sex, age, or iris color of the subject.

Contents

Presentation

The main characteristic that distinguishes physiological anisocoria is an increase of pupil size with lower light or reduced illumination, such that the pupils differ in size between the two eyes. At any given eye examination, up to 41% of healthy patients can show an anisocoria of 0.4 mm or more at one time or another. It can also occur as the difference between both pupils varies from day to day. [2] A normal population survey showed that during poor light or near dark conditions, differences of 1 mm on average between pupils was found. [3] The presence of physiologic anisocoria has been estimated at 20% of the normal population, so some degree of pupil difference may be expected in at least 1 in 5 clinic patients.[ citation needed ]

Causes

When detected during childhood, without any other symptoms and when other disorders are discarded through clinical tests, it should be considered a developmental or genetic phenomenon. Asymmetric pupil or dyscoria, potential causes of anisocoria, refer to an abnormal shape of the pupil which can happens due to developmental and intrauterine anomalies. [4] When light is shined in the abnormal eye and it remains dilated then it's a pathological small pupil.

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<span class="mw-page-title-main">Iris (anatomy)</span> Colored part of an eye

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<span class="mw-page-title-main">Amblyopia</span> Failure of the brain to process input from one eye

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<span class="mw-page-title-main">Pupillary light reflex</span> Eye reflex which alters the pupils size in response to light intensity

The pupillary light reflex (PLR) or photopupillary reflex is a reflex that controls the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retinal ganglion cells of the retina in the back of the eye, thereby assisting in adaptation of vision to various levels of lightness/darkness. A greater intensity of light causes the pupil to constrict, whereas a lower intensity of light causes the pupil to dilate. Thus, the pupillary light reflex regulates the intensity of light entering the eye. Light shone into one eye will cause both pupils to constrict.

Pupillary hippus, also known as pupillary athetosis, is spasmodic, rhythmic, but regular dilating and contracting pupillary movements between the sphincter and dilator muscles. Pupillary hippus comes from the Greek hippos meaning horse, perhaps due to the rhythm of the contractions representing a galloping horse.

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<span class="mw-page-title-main">Coloboma</span> Hole in one of the structures of the eye

A coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is present during early stages of prenatal development, fails to close up completely before a child is born. Ocular coloboma is relatively uncommon, affecting less than one in every 10,000 births.

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<span class="mw-page-title-main">Anisocoria</span> Unequal size of the eyes pupils

Anisocoria is a condition characterized by an unequal size of the eyes' pupils. Affecting up to 20% of the population, anisocoria is often entirely harmless, but can be a sign of more serious medical problems.

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A relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil, is a medical sign observed during the swinging-flashlight test whereupon the patient's pupils dilate when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.

Polycoria is a pathological 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.

<span class="mw-page-title-main">Pupillary response</span> Physiological response that varies the size of the pupil

Pupillary response is a physiological response that varies the size of the pupil, via the optic and oculomotor cranial nerve.

Pupillometry, the measurement of pupil size and reactivity, is a key part of the clinical neurological exam for patients with a wide variety of neurological injuries. It is also used in psychology.

Müllerian duct anomalies are those structural anomalies caused by errors in müllerian duct development during embryonic morphogenesis. Factors that precipitate include genetics, and maternal exposure to teratogens.

Clinicians routinely check the pupils of critically injured and ill patients to monitor neurological status. However, manual pupil measurements have been shown to be subjective, inaccurate, and not repeatable or consistent. Automated assessment of the pupillary light reflex has emerged as an objective means of measuring pupillary reactivity across a range of neurological diseases, including stroke, traumatic brain injury and edema, tumoral herniation syndromes, and sports or war injuries. Automated pupillometers are used to assess an array of objective pupillary variables including size, constriction velocity, latency, and dilation velocity, which are normalized and standardized to compute an indexed score such as the Neurological Pupil index (NPi).

References

  1. Doetsch, H. (May 1950). "Anisocoria as a physiological phenomenon". Art Wochensch. 5. 26 (20): 331–3.[ needs update ]
  2. Corbett, J.; Lam BL; Thompson HS (15 July 1987). "The prevalence of simple anisocoria". Am J Ophthalmol. 104 (1): 69–73. doi:10.1016/0002-9394(87)90296-0. PMID   3605282.
  3. London, Richard; Ellen Richrer Erringer; Harry J. Wyafr (March 1991). "Variation and Clinical Observation With Different Conditions of Illumination and Accommodation". Investigative Ophthalmology & Visual Science. 32 (3): 501–9.
  4. "Pupil Anomalies: Reaction and Red Flags". Pacifica University Oregon. Retrieved 25 November 2012.