Eye Anatomy

This page reviews the basic anatomy of the eye.

Image Credit: Rhcastilhos. And Jmarchn. [License: CC BY-SA 3.0]

Anterior segment:

Eyelids: Comprised of meibomian glands and eyelids. The inner aspect of the eyelids are lined by conjunctiva, referred to as the palpebral conjunctiva.

Cornea: Clear structure through which light is refracted to focus images on the retina. Dry eye disease can manifest as micro-abrasions on cornea.

Conjunctiva: Superficial white tissue adjacent to the cornea. “Conjunctivitis” refers to inflammation of this tissue which has numerous etiologies including infectious, inflammatory, allergic, and toxic.

Sclera: Tissue deep to conjunctiva which often can become inflammed in the setting of autoimmune conditions.

Anterior chamber: The space between the cornea and the iris which is filled with aqueous humor

Aqueous humor: Clear fluid filling the anterior chamber which brings nutrients to the eye.

Iris: Pigmented structure which determines individual’s “eye color.” It has a sphincter and dilator muscle centrally which allows for changes in size of the pupil.

Lens: Crystalline structure through which light is also refracted to focus on the retina. Over time, this structure loses its clarity at which time it is referred to as a “cataract.”

Posterior Segment:

Vitreous: Jelly-like substance which fills the posterior segment.

Retina: Neurosensory layer of the eye on which images are focused. The central portion of the retina, the macula, contains the highest density of cones and provides central vision. Pathologies such as diabetic retinopathy and macular degeneration can compromise the macula, leading to decreased vision.

Optic Nerve: Cranial nerve II, which structurally connects the eye to the brain. Optic neuropathies such as that caused by glaucoma, or vascular, inflammatory, toxic, and metabolic insults can lead to significant vision loss.

Choroid: The structure between the scleral and the retina which is rich in vascularity, thereby supplying nutrients to the posterior segment. It is part of the uveal tissue and prone to inflammation associated with autoimmune conditions.