Descemet's membrane , or posterior border membrane , is an intermediate layer between the stroma and endothelium of the cornea - the cornea of the eye . The eponymous name is given in honor of the French physician Jean Descemet (J. Descemet, 1732-1810).
| Descemet's shell | |
|---|---|
| lat l. limitans posterior corneae | |
 Human cornea. 1. corneal epithelium 2. Bowman's membrane 3. stroma of the cornea 4. Descemet's shell 5. corneal endothelium | |
 Rupture of the Descemetic membrane during keratoconus . | |
| Catalogs | |
|
Since the synthesis of collagen molecules that form the membrane is carried out by endothelial cells, in fact, the Descemet's membrane is its basement membrane . With age, its thickness in humans increases - from 3 microns at birth to 10 microns by 80 years. The layer of the membrane synthesized prior to birth adjacent to the stroma is also called the “striped zone”; it differs somewhat from the layer that later grows from the lower side of the non-banded zone . Collagen strips of different orientations in the upper zone are interleaved in increments of 110 nm. [2] Interestingly, the lower zone in women older than 70 years is approximately twice as thick as in men of a similar age; [2] this may be due to hormonal changes. [3]
The structure of a healthy Descemet shell contains collagen IV , collagen VIII , fibronectin , entactin , laminin , perlecan . [4]
Diseases and Damage
In the late stages of keratoconus , a rupture of the descemet shell may occur, leading to filling the stroma with fluid. Shell ruptures are also noted in congenital glaucoma (Haab striae, English Haab striae ), in cases of damage to the eye by obstetric forceps , when the latter are used during childbirth, [5] and with non-pass through (layered) keratoplasty . [3]
If the rupture of the membrane occurs in a healthy eye, for example, when hit by a paintball capsule, there is a chance of successful healing: endothelial cells migrate to the site of damage, synthesize the membrane substance, and pump out excess fluid from the stroma. [3]
A hernia of the Descemet sheath, or Descemetocele , develops due to a number of reasons, for example, when the graft is not fully engrafted after corneal transplantation .
Inflammatory processes in the cornea or parenchymal keratitis [6] can lead to folds of the descemet sheath . [7]
With Fuchs endothelial dystrophy , most often affecting women, the shell thickness increases to 20 or more microns, its structure changes. An early form of the disease is associated with mutations in the COL8A2 gene , which encodes collagen VIII , which is part of the descemet membrane. [eight]
As with Fuchs dystrophy, and with other diseases of the eye, as well as stress or damage to endothelial cells, they can begin to produce Descemet's membrane of an abnormal structure. In 1982, a study of 19 diseases was carried out and three general types of disorders were proposed: [9]
- the formation of a striped posterior (- that is, posterior, adjacent not to the stroma, but to the endothelium) collagenous layer;
- the formation of a fibrillar posterior collagenous layer with randomly arranged fibrils with a diameter of 20-30 nm;
- the formation of a fibrocellular posterior collagenous layer containing fibroblasts
Notes
- ↑ 1 2 Foundational Model of Anatomy
- ↑ 1 2 Johnson DH, Bourne WM, Campbell RJ The ultrastructure of Descemet's membrane. I. Changes with age in normal corneas (Eng.) // Arch. Ophthalmol. : journal. - 1982. - December ( vol. 100 , no. 12 ). - P. 1942-1947 . - PMID 7150061 . (inaccessible link)
- ↑ 1 2 3 Dohlman, Claes H .; Smolin, Gilbert; Azar, Dimitri T. Smolin and Thoft's The cornea: scientific foundations and clinical practice. - Hagerstwon, MD: Lippincott Williams & Wilkins, 2005 .-- ISBN 0-7817-4206-4 .
- ↑ Frank J. Larkin; Thomas Reinhard. Cornea and External Eye Disease (Essentials in Ophthalmology). - Berlin: Springer, 2008 .-- ISBN 3-540-33680-X .
- ↑ Michael S. Loughnan; Adrian Bruce. Anterior Eye Disease and Therapeutics AZ. - Oxford: Butterworth-Heinemann, 2003 .-- ISBN 0-7506-5261-6 .
- ↑ L. Holbach. Applied Pathology for Ophthalmic Microsurgeons. - Berlin: Springer, 2008 .-- ISBN 3-540-24189-2 .
- ↑ Descemet Membrane Folds - eMedicine
- ↑ Fuch's endothelial dystrophy 1 - OMIM catalog
- ↑ Waring GO Posterior collagenous layer of the cornea. Ultrastructural classification of abnormal collagenous tissue posterior to Descemet's membrane in 30 cases (Eng.) // Arch. Ophthalmol. : journal. - 1982. - January ( vol. 100 , no. 1 ). - P. 122-134 . - PMID 7055463 . (inaccessible link)