Human Eye Anatomy and Function: Key Structures and Visual Processing

Sclera

The tough, outer fibrous coat of the eye (the "white" of the eye).

Cornea

The clear, front part of the sclera; helps focus light as it enters the eye.

Choroid

Middle layer of the eye, filled with blood vessels that nourish the retina.

Aqueous Humor

Watery fluid that fills the anterior cavity (in front of the iris and lens).

Vitreous Humor

Thicker, jelly-like fluid that fills the posterior cavity (behind the iris and lens).

Iris

Colored part of the eye; controls how much light enters by adjusting the size of the pupil.

Pupil

Opening in the middle of the iris that lets light into the eye. Dilates in dim light (gets larger). Constricts in bright light (gets smaller).

Lens

Transparent, biconvex structure behind the pupil; focuses light onto the retina. Shape is adjusted by suspensory ligaments.

Suspensory Ligaments

Fibers attached to the lens; help change its shape to focus on near or distant objects.

Retina

Inner layer of the eye; contains photoreceptors (rods and cones) that respond to light.

Rod Cells

About 120 million; detect light and dark (black-and-white vision).

Cone Cells

600-700 million; detect colors and allow color vision. Concentrated in the fovea.

Fovea

Small central area of the retina with the sharpest vision (high density of cones).

Optic Nerve

Carries impulses from the retina to the visual cortex of the brain.

Blind Spot

Location where the optic nerve passes out of the eye; no photoreceptors are present.

Visual Cortex

Part of the brain that interprets electrical signals from the optic nerve as images.