Aqueous humor

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Anatomical structure of the eye (aqueous humor light blue)

The aqueous humor ( humor aquosus ) is a clear body fluid in the anterior and posterior chambers of the eye .

composition

The aqueous humor is similar in consistency to blood serum , but colorless because it contains less protein and no bilirubin . It consists of 98% water , in which mainly amino acids (from the ciliary muscles), electrolytes , ascorbic acid , lactic acid , glutathione and immunoglobulin G (IgG antibodies , no IgD , IgA or IgM ) are dissolved, as well as traces of hydrogen peroxide .

metabolism

The water content of the aqueous humor is formed from the carbonic acid of the blood by α-carbonic anhydrases of the radiative body tissue. A human eye produces around 3 to 9 ml of aqueous humor per day with an eyeball volume of around 6.5 ml.

Path of aqueous humor

Scheme of aqueous humor flow

The aqueous humor is formed on the ciliary processes , released into the posterior chamber and also passes through the pupil into the anterior chamber. At the front of the iris , the aqueous humor rises due to the higher temperature, and then sinks on the cooler back of the cornea . About 85% of the aqueous humor flows through the sieve-like network in the chamber angle ( angulus iridocornealis ) into Schlemm's canal and returns to the bloodstream ( trabecular drainage) via the plexus venosus sclerae , a venous network in the sclera . On the other hand, around 15% of the outflow occurs as uveoscleral outflow via the vessels of the ciliary body and the iris.

Similar to the blood-brain barrier, ultrastructural cell seals ensure a highly specific chemical composition of the aqueous humor ( blood-aqueous humor barrier ).

function

The aqueous humor contains nutrients for the lens and cornea endothelium and, with its content of immune factors and its circulation, serves to remove potentially damaging agents from the interior of the eye. It is also involved in the development of intraocular pressure .

Diseases

Loss of aqueous humor after opening the eyeball e.g. B. during operations or accidents can lead to choroidal swelling, especially if the resulting pressure loss is not compensated for in a short time. Escaping aqueous humor can be detected with the help of the Seidel test .

An overproduction of aqueous humor or disturbances of the aqueous humor outflow can lead to an increase in intraocular pressure and thus increase the risk of glaucoma (glaucoma).

A defect in the blood-aqueous humor barrier can lead to clouding and sticking.

literature

  • Albert J. Augustin: Ophthalmology. 3rd, completely revised and expanded edition. Springer, Berlin a. a. 2007, ISBN 978-3-540-30454-8 .
  • Goldmann Hans: The transfer of fluorescein from the blood into aqueous humor of normal people , 1949, Experientia Vol. 5, Ed. 7, pages 295-296
  • Goldmann Hans: discharge pressure, minute volume and resistance of the aqueous humor flow of humans , 1951, Doc Ophthalmol 5/6, page 652-671
  • Yves Robert: intraocular pressure clinic . 1st edition. Walter de Gruyter GmbH & Co.KG, Bern 2015, ISBN 978-3-11-042188-0 , p. 220 .

Individual evidence

  1. ↑ DK Sen, GS Sarin, K. Saha: Immunoglobulins in human aqueous humor. In: Br J Ophthalmol. Volume 61, No. 3, March 1977, pp. 216-217. PMC 1042917 (free full text)
  2. ↑ David M. Gamm: Aqueous humor In: Encyclopaedia Britannica online, accessed January 23, 2015.
  3. ↑ Manik Goel, Renata G. Picciani, Richard K. Lee, Sanjoy K. Bhattacharya: Aqueous Humor Dynamics: A Review. In: Open Ophthalmol J. Volume 4, 2010, pp. 52-59, doi: 10.2174 / 1874364101004010052 .
  4. ↑ Antoinette Pirie: Glutathione peroxidase in lens and a source of hydrogen peroxide in aqueous humor. (PDF) In: Biochem. J. Volume 96, 1965, pp. 244-253.
  5. ↑ Carl Erb, Gerhard K. Lang, Gabriele E. Lang: Schlaglicht Augenheilkunde: Glaucoma . Georg Thieme Verlag 2014, page 102. ISBN 978-3-13-200111-4
  6. ^ Albert J. Augustin: Physiology for the Oral Examination: Questions and Answers . 2, illustrated edition. Springer-Verlag, 2013, ISBN 978-3-642-97698-8 , pp. 191 (217 p., Limited preview in Google Book search).
  7. ^ Franz Grehn: Ophthalmology. Springer Verlag 2013, page 334. ISBN 978-3-662-05918-0