PDC Test - The Eye
You can earn 0.25 PDC by passing the exam following this article, which has been approved for publication by NCRA's Council of the Academy of Professional Reporters.
The questions are based on the material in the article but some may require additional research. Send your answer sheet to NCRA's Continuing Education Office, 8224 Old Courthouse Road, Vienna, VA 22182, and enclose a check for $40 (member) or $50 (non-member) to cover the processing fee.
The eyeball frequently is compared to a camera. The analogy is not entirely true, but we can learn a few things about the eye by thinking of it in terms of various parts of a camera. Both the eyeball and the camera are light-tight containers with dark inside walls. The camera is shaped like a box and the eyeball is spherical, of course. The walls of the camera usually are made of a rigid metal or plastic. The outside of the eyeball, the sclerotic coat, is made of tough fibrous tissue. The eyeball is further protected by its location in the bony orbit of the skull. The orbit is lined with a cushion of fatty tissue to protect the eye from shock damage. The eyeball has a layer just inside the sclerotic coat, the choroid, which is filled with blood vessels to nourish the living tissues of the eye.
Both the camera and the eye have a lens to focus the image on a light-sensitive surface. The light-sensitive surface in the camera is the roll or plate of film. In the eye it is a layer of light-sensitive nerve cells and is called the retina. In the camera, the distance between the lens and the film usually can be changed to keep the image in focus for objects both near and far away. In the eye, the shape of the lens is changed automatically by small muscles so that we can see clearly objects at various distances.
A further similarity is that of the iris, the curtain at the front of the eye that can be opened or closed to permit various amounts of light to pass through the lens. In the camera, the iris may be controlled by energy from a photoelectric cell or it can be adjusted by hand. The iris of the eye adjusts automatically to changes in light intensity, again by the action of tiny muscles it contains. The opening in the iris of the eye is called the pupil.
In the cases of both the eye and the camera, simple lenses do not produce clear images without some "correction." The outer edges of the lenses bend rays of light at different angles than do the center parts of the lenses. Camera lenses are corrected by making them from combinations of different kinds of glass. The human eye is partly corrected by nature's design of the cornea, a transparent extension of the sclerotic coat in front of the pupil. The curvature of the cornea varies slightly to compensate for visual errors produced by edges of the lens. In some people, however, the surface of the cornea becomes irregular and vision is blurred. This condition is called astigmatism.
The front of the cornea is protected by a smooth, transparent layer of tissue called the conjunctiva. A similar membrane covers the inner surfaces of the eyelids. The eyelids also contain dozens of tiny tarsal glands that secrete an oil to lubricate the surfaces of the eyeball and eyelids. Still further protection is provided by the lacrimal gland, located at the outer edge of the eye socket. It secretes tears to clean the protective membrane and keep it moist.
The region between the cornea and the lens is filled with a salty, clear fluid known as the aqueous humor. The eyeball behind the lens is filled with a jelly-like substance called the vitreous humor. The innermost layer of the eyeball, the retina, is itself made up of eight layers of nerve tissue. Most of the layers contain nerve fibers or nerve nuclei. But the layer most directly involved in vision contains specialized nerve cells called rods and cones. They get their names from the rod- and cone-like shapes seen when the layer is viewed under a microscope. The rods are more sensitive to light than the cones. The cones, on the other hand, are sensitive to colors. When we are trying to see an object at night, perhaps by moonlight, we depend upon the rods. The faint amounts of light passing through the lens fall upon the retina and stimulate the rods which transmit, through the optic nerve, the messages that produce the visual image in the brain.
As the intensity in light increases, cones begin to dominate the action of image formation in the brain. The rods might continue firing messages to the brain in bright light, but they apparently contribute very little to the image in such cases. Animals such as rats and owls, which sleep during the day and forage for food at night, have only rods in the retinas of their eyes.
Visual acuity may be affected by several types of eye defects. Astigmatism, mentioned earlier, is one abnormal condition. Other common defects are myopia (near sightedness) and hyperopia (farsightedness). Myopia occurs when the rays of light entering through the lens are focused in the vitreous humor, in front of the retina. Hyperopia results when the image is focused, theoretically, behind the eyeball. Both near- and farsightedness may result from abnormal curvature of the lens or cornea or from abnormal shape of the eyeball.
This article and the accompanying tests were prepared by Nancy Patterson, who has served on various committees and boards for NCRA and is the winner of the 1990 DSA award. Nancy is the director of Bryan College of Court Reporting in Los Angeles, California. The article "The Eye" is reprinted by permission of the American Medical Association from The Human Machine, copyright 1979.
Test for "The Eye"
1. The sclera is normally
A. blue or brown
C. pinkish or red
2. The orbit or orbita of the eye is formed by
A. a hollow in the frontal bone
B. the juncture of the mandible
C. three bones
D. many bones
3. What furnishes the blood supply to the retina?
4. As in a camera, there is an aperture in the eye to admit light called the
B. ciliary body
5. The rods and cones are specialized nerve cells in the
6. The pigmented structure which gives eyes their color is the
7. If the light rays are focused in front of the retina, the subject has
8. "Tarsal" refers to the inside of the eyelid or to the
9. The red eminence at the medial angle of the eye is called the
A. fovea centralis
C. lacrimal punctum
10. Deviation of the visual axis of the eye
11. An involuntary rapid movement of the eyeball is
12. Cross-eye is the same as
13. Wall-eye is the same as
14. The aqueous humor fills
A. only the anterior chamber
B. only the posterior chamber
C. the anterior and posterior chambers
D. the anterior chamber and vitreous chamber
15. If rays of light entering the eyeball are brought to focus directly on the retina, it is called
16. If you have difficulty seeing objects up close, you have
17. Abnormal elongation of the eyeball would be likely to result in
18. The Snellen chart should be used to test for
C. intraocular pressure
D. refractive error
19. Increased intraocular pressure causes
20. The transparent cornea is a modification of the
21. Pilocarpine hydrochloride is used in the treatment of
A. a cataract
B. a sty
22. Bacitracin would be likely to be used to treat
23. The vascular coat of the eyeball is the
24. The optic is the
A. first cranial nerve
B. second cranial nerve
C. third cranial nerve
D. fourth cranial nerve
25. Contraction of the pupil is called
|Answer Sheet for "The Eye"
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