Hippus

Pupillary hippus, also known as pupillary athetosis, is spasmodic, rhythmic, but regular dilating and contracting pupillary movements between the sphincter and dilator muscles.[1][2] Pupillary hippus comes from the Greek hippos meaning horse, perhaps due to the rhythm of the contractions representing a galloping horse.[3] Notably, hippos in antiquity referred to involuntary eye movements which are nowadays called nystagmus.[4] It is particularly noticeable when pupil function is tested with a light,[2] but is independent of eye movements or changes in illumination.[1] It is usually normal, however pathological hippus can occur.[2][3]

Pathologic hippus, the phenomenon of increased oscillation or their amplitude, is associated with aconite poisoning,[5] altered mental status, trauma, cirrhosis, and renal disease; suggesting a common pathway of frontal lobe dysfunction.[6] A retrospective study of 117 hospitalized patients with hippus noted an increased 30-day mortality when compared to controls and adjusted for other factors.[6]

## See also

* Athetosis
* Anisocoria \- condition characterized by an unequal size of the eyes' pupils.

## References

1. ↑ 1.0 1.1 McLaren J. W.; Erie J. C.; Brubaker R. F. (1992). "Computerized analysis of pupillograms in studies of alertness". Investigative Ophthalmology and Visual Science 33: 671–6.
2. ↑ 2.0 2.1 2.2 Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainesville, Florida: Triad Publishing Company, 1990.
3. ↑ 3.0 3.1 Beatty, J., & Lucero-Wagoner, B. (2000). The pupillary system. In J. T. Cacioppo, L. G. Tassinary & G. G. Bernston (Eds.), The handbook of psychophysiology (2nd ed.) (pp. 142-162). USA: Cambridge University Press.
4. ↑ Gerb, Johannes; Brandt, Thomas; Huppert, Doreen (July 2023). "Historical descriptions of nystagmus and abnormal involuntary eye movements in various ancient cultures" (in en). Science Progress 106 (3). doi:10.1177/00368504231191986. ISSN 0036-8504. PMID 37642983. PMC 10469245. http://journals.sagepub.com/doi/10.1177/00368504231191986.
5. ↑ Forensic and State Medicine: Reddy
6. ↑ 6.0 6.1 "Increased hospital mortality in patients with bedside hippus". Am J Med 121 (3): 239–45. 2008. doi:10.1016/j.amjmed.2007.09.014. PMID 18328309.

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