The cornea, the transparent front surface of the eye, plays a role in focusing light onto the retina. Within this structure lies Descemet’s membrane.
Unveiling Descemet’s Membrane
Descemet’s membrane is a thin, transparent basement membrane within the cornea. It is the innermost layer, positioned between the corneal stroma and the corneal endothelium. Endothelial cells lining the posterior surface of the cornea secrete this membrane.
The membrane continuously thickens throughout life, starting at about 3 micrometers (µm) at birth and reaching 8 to 10 µm in adults. Composed primarily of type IV and type VIII collagen, along with other proteins like laminin, its structure provides resilience and a stable foundation for the endothelial layer.
The Membrane’s Essential Functions
Descemet’s membrane maintains corneal health and clarity. It acts as a protective barrier, preventing fluid from the aqueous humor from entering the corneal stroma. This barrier function helps regulate corneal hydration and prevent swelling.
The membrane also provides structural support for the corneal endothelium. Endothelial cells pump excess fluid out of the cornea, a process important for maintaining corneal transparency. By supporting these cells, Descemet’s membrane indirectly contributes to the cornea’s clarity.
When Descemet’s Membrane is Affected
When Descemet’s membrane is compromised, it can lead to various eye conditions affecting vision. One is Fuchs’ Endothelial Dystrophy (FED), a genetic disorder impacting the corneal endothelium and Descemet’s membrane. In FED, abnormal growths called “guttae” develop on Descemet’s membrane. This leads to progressive loss and dysfunction of endothelial cells, resulting in corneal swelling and blurred vision, often more noticeable in the mornings.
Another issue is Descemet’s membrane detachment (DMD), the separation of the membrane from the corneal stroma. This can occur due to trauma, but it is most commonly a complication of intraocular surgery, such as cataract removal. When detached, aqueous humor can enter the space, causing corneal edema and potentially affecting vision.
Acute hydrops, a complication in advanced keratoconus, also involves Descemet’s membrane. A rupture in Descemet’s membrane allows aqueous humor to suddenly leak into the corneal stroma, causing rapid corneal swelling and clouding. This event can lead to sudden vision loss and eye pain. While it often resolves on its own, it can leave a permanent scar that impairs vision.