The Eye and Vision

By Ahmad Fauzan

E-mail: d.344.af@gmail.com

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