Ocular hypotony

Ocular hypotony, ocular hypotension or hypotony is the medical condition in which intraocular pressure (IOP) of the eye is very low.

Description

Normal IOP ranges between 10–20 mm Hg.[1] The eye is considered hypotonous if the IOP is ≤5 mm Hg (some sources say IOP less than 6.5 mmHg).[2][3]

Types

Ocular hypotony is divided into statistical and clinical types. If intraocular pressure is low (less than 6.5 mm Hg) it is called statistical hypotony, and if the reduced IOP causes a decrease in vision, it is called clinical.[4]

Causes

Hypotony may occur either due to decreased production of aqueous humor or due to increased outflow. Hypotony has many causes including post-surgical wound leak from the eye, chronic inflammation within the eye including iridocyclitis, hypoperfusion, tractional ciliary body detachment or retinal detachment.[5] Eye inflammation, medications including anti glaucoma drugs, or proliferative vitreoretinopathy causes decreased production.[6] Increased outflow or aqueous loss may occur following a glaucoma surgery, trauma, cyclodialysis cleft or retinal detachment.[6]

Complications

Decreased IOP may lead to phthisis bulbi.[3] Hypotony maculopathy is another complication caused by very low IOP.[7]

Treatment

Treatment of hypotony is depending on the cause of the condition.[6] Chronic ocular hypotony may be treated with intraocular injection of sodium hyaluronate.[8] If the cause of hypotony is an over filtering bleb, cycloplegia using atropine may be used.[2]

References
  1. "Eye Pressure". American Academy of Ophthalmology. 19 January 2018.
  2. N.Y, Valerie Trubnik, MD, FACS, Mineola. "Managing Hypotony After Trabeculectomy". www.reviewofophthalmology.com.
  3. Schmack, Ingo; Völcker, Hans E; Grossniklaus, Hans E (1 January 2010). "Chapter 54 - Phthisis bulbi". Ocular Disease. W.B. Saunders. pp. 415–423. ISBN 978-0-7020-2983-7.
  4. Thomas, Merina; Vajaranant, Thasarat S.; Aref, Ahmad A. (December 2015). "Hypotony Maculopathy: Clinical Presentation and Therapeutic Methods". Ophthalmology and Therapy. 4 (2): 79–88. doi:10.1007/s40123-015-0037-z. ISSN 2193-8245. PMC 4675727. PMID 26253854.
  5. "Ocular Hypotony: Background, Pathophysiology, Epidemiology". 19 July 2021.
  6. Fine, Howard F.; Biscette, O'neil; Chang, Stanley; Schiff, William M. (January 2007). "Ocular hypotony: a review". Comprehensive Ophthalmology Update. 8 (1): 29–37. ISSN 1527-7313. PMID 17394757.
  7. "Hypotony Maculopathy - EyeWiki". eyewiki.aao.org.
  8. Küçükerdönmez, C.; Beutel, J.; Bartz-Schmidt, K. U.; Gelisken, F. (1 February 2009). "Treatment of chronic ocular hypotony with intraocular application of sodium hyaluronate". British Journal of Ophthalmology. 93 (2): 235–239. doi:10.1136/bjo.2008.143834. ISSN 0007-1161. PMID 18829633. S2CID 36520175.
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