Lamina cribrosa sclerae

Posteriorly, the sclera is pierced by the optic nerve and is continuous with the nerve's fibrous sheath and hence with the dura mater. Where the nerve pierces the sclera, the latter has the appearance of a perforated plate, the lamina cribrosa sclerae, the minute orifices in which transmit the optic nerve's fascicles. A larger, central aperture in this structure is traversed by the central retinal artery and vein. The lamina cribrosa is the weakest part of the sclera and bulges outwards in the condition of a cupped disc when intraocular pressure is raised chronically as in the condition of glaucoma.