The Eye and Its Function

Vision

Is one of the distal senses which utilizes the physical characteristics of light.

The eye is the receptor organ of vision, and it is a very amazing device.

What you know of your outside environment comes from this important organ.

Vision

The stimuli for seeing are light waves which are waves of radiant energy coming from the sun.

They are described in terms of wave lengths and the unit of measurement is the millimicron (one million of a millimeter)

A Cross-Section of the Human Eye

The Eye utilizes Two Basic Properties of Light

Brightness- the intensity of light and is considered as the amount of light energy that the eye receives

Color- The color of light is

determined by its frequency or wavelength.

Eyes Are very important organs and as such

they are well protected. The bony sockets, the eye lids. The eye

lashes and also the eye brows protect the eyes.

Parts of the Eye

Cornea

The cornea forms a bulge at the front of the eye and since it is transparent light can enter the eye.

It serves as a protection of the eye. It is a white though membrane which is

a continuation of the sclera which is the outermost protective coat of the eye.

Iris Is a group of muscles which operates

by reflex action and gives color of the eye.

In a bright place, the contraction of the iris makes the pupil smaller, thus controlling much of the brightness of light.

In a dim light, the iris expands and the pupil becomes larger.

Iris

Light then passes from the pupil to the lens which can be adjusted by another group of muscles to bring objects into focus.

The lens adjust the light rays so that whatever one is looking at is sharply focused on the retina.

Retina It is the true organ of

vision. It is also the photo

sensitive area of the eye.

It has two receptor cells, the rods and the cones, so named for their shapes.

Rods Are slender nerve cells. There are about 100 million rods

distributed unevenly on the retina of the eye.

It is used for twilight vision or low intensity and enable one to make colorless discrimination.

Are sensitive to tiny amount of light. Only the rods are functioning when one

sees in very dim light.

Cones Are thicker and cone-

shaped. There are 6 million cones

distributed unevenly on the retina of the eye.

Are concentrated in the center of the retina.

Are used in for daytime vision to enable one to discriminate brightness and hue or color.

Two important parts of Retina

Fovea – is in the central region where cones are concentrated.

Two important parts of Retina

Blind spot – is the area where the nerve fibers from all over the eye converge to form the optic nerve that carry impulses to the brain.

Color Vision When a person tries

to described or make a report or what he has seen, he usually tells the color by using what we called the three dimension of color – hue, brightness and saturation

Hue Refers to the name of

colors. Follows the order from

violet which has the shortest wave length to red which has the longest wavelength.

Brightness It is the energy

source of light. It is also

associated with intensity of the stimulus.

Yellow as a hue usually appears brighter than red and blue.

Saturation Refers to the purity

or richest of color. Highly constructed

colors appear to be pure hues and there is no tint of gray added.

Colors of low saturation appear close to gray.