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.