The Anatomy of the Eye

Cornea

the clear surface at the front of the eye that allows light in. Begins the process of bending light to focus on the retina (in the back of the eye)

Sclera

The white of the eye. Adds protection.

Iris

The colored part of the eye; two muscles with an opening in the middle

Anterior chamber

Between the cornea and the iris; a fluid filled space

Pupil

The opening surrounded by the iris

Dim light

iris opens to allow the pupil to expand

Bright light

iris contracts and the pupil narrows

Pupillary reflex

a process that helps regulate the amount of light reaching the retina and protecting photoreceptors. 

The lens

The adjustable focusing element of the eye located just behind the iris.

Accommodation

the eye's ability to adjust its focus to see objects clearly at different distances, involving the convergence of both eyes, contraction of the ciliary muscles to change lens shape, and pupillary constriction. 

Retina

The paper-thin layer of cells at the back of the eye where transduction occurs

Retinal image

The light projected onto the retina

Photoreceptors

Convert light into a neural signal and begins the process of sending visual signals to the brain

Light-sensitive photopigments

rods and cones

Rod Function

Functions best in dim light, poorly, or not at all in bright light. Detail vision is poor. Does not distinguish colors.

cones

iodopsin

Rod Location

Mostly in periphery of retina

Rod Receptive Field

Large, due to convergence on ganglion cells; contributes to light sensitivity

Cone function

functions best in bright light, poorly or not at all in dim light. Detail vision is good. Subset distinguishes among colors.

Cone location

mostly in fovea and surrounding area

Cone receptive field

small, with one or a few cones converging on a single ganglion cell; contributes to detail vision

Fovea

center of retina, high density of photoreceptors

Peripheral

sides of retina, low density of photoreceptors

Photoreceptors

Located at the back of the eye (along the retina). They synapse (or connect) with horizontal cells and bipolar cells.

Bipolar cells

convey signal from photoreceptors to the next inner layer