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Cornea – The transparent front part of the eye that covers the iris, pupil, and anterior chamber and transmits and focuses light into the eye.

Cone – A type of light-sensitive cell in the retina that provides sharp central vision and color vision.

Conjunctiva – A thin clear moist membrane that coats the inner surfaces of the eyelids and the outer surface of the eye.

Fovea – The central part of the macula that contains the largest concentration of cone cells in the eye and is responsible for central, high-resolution vision.

Lens – A transparent body situated behind the iris in the eye that, along with the cornea, focuses light on the retina.

Limbus – The edge of the cornea bordering the sclera.

Macula – An oval shaped highly pigmented yellow spot near the center of the retina of the human eye. It has a diameter of around five millimeters and contains special light-sensitive cells that allow fine details to be seen.

Optic Nerve – (Cranial Nerve II) transmits visual information from the retina to the brain.

Pupil – The opening of the iris that determines the amount of light that is let into the eye.

Retina – The nerve layer that lines the back of the eye senses light and creates impulses that travel through the optic nerve into the brain.

Rod – A type of specialized light-sensitive cell in the retina that provides side vision and the ability to see objects in dim light (night vision).

Sclera – The tough white outer coat over the eyeball that covers approximately the posterior five-sixths of the surface. The sclera is continuous in the front of the eye with the cornea and in the back of the eye with the external sheath of the optic nerve.

Stereotactic Radiotherapy – A form of radiation treatment that tightly focuses upon a small area of the body, typically using multiple beams.

Vitreous – A clear, jelly-like substance that fills the middle of the eye.