What is the lamina cribrosa?

• A. A loop of scleral tissue.
• B. A sieve-like connective tissue structure at the optic nerve head through which axons pass.
• C. A cartilage plate at the posterior globe.
• D. A vascular network within the retina.

Answer: (B)

The lamina cribrosa is a sieve-like plate of connective tissue located in the scleral canal at the optic nerve head. It forms a lattice of collagen beams with multiple openings through which the retinal ganglion cell axons pass as they exit the eye to form the optic nerve. This perforated structure provides mechanical support to the nerve fibers as they traverse the optic nerve, marking the transition between intraocular and intraorbital portions. It is not a loop of scleral tissue, a cartilage plate, or a vascular network within the retina.