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The Eye and Vision
By Ahmad Fauzan
E-mail: [email protected]
Lecturer and Researcher
Nursing Basic Science Department
Muhammadiyah Gombong University
Kind of senses General senses of touch
Temperature Pressure Pain
Special senses1. Sight 2. Smell3. Taste4. Hearing5. Equilibrium
The Eye and Vision
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
· 70 percent of all sensory receptors are in the eyes
· Each eye has over a million nerve fibers
· Protection for the eye· Most of the eye is
enclosed in a bony orbit
· A cushion of fat surrounds most of the eye
Eye ReflexesInternal muscles are controlled by the
autonomic nervous systemBright light causes pupils to constrict through
action of radial and ciliary musclesViewing close objects causes accommodation
External muscles control eye movement to follow objects
Viewing close objects causes convergence (eyes moving medially)
Lens Accommodation:Light must be
focused to a point on the retina for optimal vision
The eye is set for distance vision (over 20 ft away)
The lens must change shape to focus for closer objects
FOKUS PENGLIHATAN DEKAT:
1. Kontraksi m. Ciliaris
2. Corpus ciliaris
FOKUS PENGLIHATAN JAUH:
1. Relaksasi m. Ciliaris
2. Corpus ciliaris relaksasi
Images Formed on the Retina
© Omikron/Photo Researchers
ABC
A
B
Cone Sensitivity
There are three types of cones
Different cones are sensitive to different wavelengths
Color blindness is the result of lack of one cone type
Visual Pathway:
1. Photoreceptors of the retina
2. Optic nerve3. Optic nerve
crosses at the optic chiasma
4. Optic tracts5. Thalamus (axons
form optic radiation)
6. Visual cortex of the occipital lobe
Fig. 5.15 Color blindness and color weakness. (a) Photograph illustrates normal color vision. (b) Photograph is printed in blue and yellow and gives an impression of what a red-green color-blind person sees. (c) Photograph simulates total color blindness. If you are totally colorblind, all three photos will look nearly identical.
Colour BlindTrikromatisDikromatisMonokromatis
