Human Eye Anatomy and Visual Processing: Key Concepts and Theories

Cornea

the eye's clear, domelike surface that covers the front of the eye and helps focus incoming light.

Aqueous Humor

the fluid between the cornea and the iris/lens that helps maintain eye pressure and shape.

Iris

colored part of the eye; a ring of muscle tissue that adjusts the size of the pupil to regulate the amount of incoming light.

Pupil

adjustable opening in the center of the iris through which light enters the eye.

Lens

transparent structure behind the pupil that changes shape (accommodation) to help focus images on the retina.

Retina

the light-sensitive inner surface of the eye; contains the receptor rods and cones and layers of neurons.

Fovea

the central focal point in the retina, where cone receptors are highly concentrated; produces the sharpest vision.

Optic Nerve

the nerve that carries neural impulses from the retina to the brain.

Rods

retinal receptors that detect black, white, and gray; highly sensitive in dim light; good for peripheral vision.

Cones

retinal receptors concentrated near the center (fovea), responsive in bright light, and sensitive to color detail.

Blind Spot

point at which the optic nerve leaves the eye, creating an area with no receptor cells.

Visual Accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina.

Farsighted / Nearsighted

refractive errors of the eye—farsighted means nearby objects are blurry; nearsighted means distant objects are blurry.

Dark Adaptation / Light Adaptation

the eye's adjustment to low / bright light conditions over time.

Trichromatic Theory

theory that retina has three types of color receptors sensitive to red, green, blue.

Opponent-Process Theory

theory that opposing retinal processes (red-green, blue-yellow, black-white) enable color vision.

Afterimage Effect

visual illusion of continuing sensation after a stimulus is removed (often in opponent-color pair).

Color Blindness

inability to distinguish certain colors; types include red/green, yellow/blue, or complete (monochromacy).

Feature Detectors

specialized neurons in the visual cortex that respond to specific features of visual stimuli, such as edges, angles, or motion.

Parallel Processing

simultaneous processing of several dimensions of a stimulus (such as color, shape, motion) in vision.