The Sclera of eye ball is a dense white fibrous membrane forming about four fifths of the fibrous tunic of the eyeball.
Thickest in the vicinity of the posterior pole, it thins at the equator and increases in thickness toward the junction with the cornea.
It is often pigmented. When non-pigmented it shows a bluish tinge.
Its external surface gives insertion to ocular muscles and is covered in front by the bulbar conjunctiva.
The internal surface is attached to the chorioid coat by pigmented connective tissue -the lamina fusca.
The anterior border is oval, the long axis being transverse and is continuous with the cornea.
The sclera here appears to form a bevel in which the cornea is fixed. Near the corneoscleral junction, there is a circular venous plexus, the plexus venosus sclerae (sinus venosus sclerae or canal of Schlemm).
The canal will be described later under the iris angle.
The optic nerve pierces the posterior part of the sclera a little below and lateral to the posterior pole (in the postero-ventrolateral quadrant).
It composed of interlacing bundles of white fibres and few elastic fibres.
