The sclera or sclera (Latin sclera ) is a white, opaque membrane that forms the larger, posterior part of the fibrous sheath of the eyeball.
It has the shape of a ball cut at the front end where the cornea is located, and continues on it and together with it forms the entire eyeball. In addition to this opening, there are even smaller openings on the sclera for the passage of nerves and blood vessels. The sclera forms together with the cornea in the second embryonic month, and is initially transparent like the cornea. The sclera is avascular (no blood vessels) and makes up 80% of the eye’s surface. The thickness of the sclera is different, it depends on the size of the bullbus (hypermetropes have a thicker sclera, and myopes have a thinner sclera).
Scleral thickness:
- In the muscle area 0.3 mm
- In the area of the optic nerve 1 mm
- In the limbus area 0.8 mm
The strength of the sclera keeps the eyeball stable.
From the outside to the inside, we distinguish 3 layers:
- Episclera
- Stroma
- Lamina fusca
In the sclera near the limbus (the border between the sclera and the cornea) there is Schlemm’s canal ( canalis Schlemmi ) which serves for the outflow of aqueous humor. Schlemm’s canal is important in regulating intraocular pressure.
The function of the sclera is to preserve the eye pressure, it also serves as a grip for the eye muscles that move the eye in all directions.
Inflammation of sclera – sclera:
- Episcleritis
- Scleritis
Autor:
bc. Livio Svržnjak, optometrist
