Eye and Ear Assessment and Procedures

LEARNING OBJECTIVES	PROCEDURES
The Eye
1. Define visual acuity. 2. State the cause and visual difficulty of each of the following: Myopia Hyperopia Astigmatism Presbyopia 3. Explain the differences between an ophthalmologist, an optometrist, and an optician. 4. Explain the significance of the top and bottom numbers next to each line of letters on the Snellen eye chart. 5. Explain the difference between congenital and acquired color vision defects. 6. List the reasons to perform an eye irrigation and an eye instillation.	Assess distance visual acuity. Assess near visual acuity. Assess color vision. Perform an eye irrigation. Perform an eye instillation.
The Ear
7. Identify conditions that may cause conductive and sensorineural hearing loss. 8. List and describe the ways in which hearing acuity can be tested. 9. List the reasons to perform an ear irrigation and an ear instillation.	Perform an ear irrigation. Perform an ear instillation.

Introduction to the Eye

The medical assistant is responsible for performing a variety of assessments and procedures that involve the eye. An understanding of the structure and function of the eye is essential to mastering skills in these areas. Refer to Chapter 10 to review the structure and function of the eye.

A visual acuity test is usually part of the routine physical examination. This test is a screening test to detect deficiencies in vision.

The medical assistant may also be responsible for assessing color vision with the use of specially prepared colored plates. As a result of this testing, color blindness can be detected. Color blindness is an inability to distinguish certain colors; the most common problem is with the colors red and green. Color blindness is particularly significant if the patient is involved in an activity that relies on the ability to distinguish colors, such as electronics and interior decorating.

The medical assistant is responsible for performing or teaching the patient to perform eye irrigations and instillations. Irrigation is washing a body canal with a flowing solution. Instillation is dropping a liquid into a body cavity. Eye irrigations and instillations should be performed using the important principles of medical asepsis outlined in Chapter 17.

Visual Acuity

Visual acuity refers to acuteness or sharpness of vision. A person with normal visual acuity can see clearly and is able to distinguish fine details close up and at some distance.

Errors of refraction are the most common causes of defects in visual acuity (Figure 21-1). Refraction refers to the ability of the eye to bend the parallel light rays coming into it so that they can be focused on the retina. An error of refraction means that the light rays are not being refracted or bent properly and are not adequately focused on the retina. A defect in the shape of the eyeball can cause a refractive error. Errors of refraction can be improved with corrective lenses.

Figure 21-1 Diagram of normal refraction compared with myopia (nearsightedness) and hyperopia (farsightedness), which are errors of refraction that cause visual defects.

A person who is nearsighted has a condition termed myopia. The eyeball is too long from front to back, causing the light rays to be brought to a focus in front of the retina. A myopic person has difficulty seeing objects at a distance and may squint and have headaches as a result of eyestrain. A corrective lens (e.g., eyeglasses, contact lenses) or laser eye surgery can correct this condition, which then allows the light rays to come to a focus on the retina.

A person who is farsighted has a condition known as hyperopia. The eyeball is too short from front to back, resulting in a different type of refractive error, in which the light rays are brought to a focus behind the retina. The individual has difficulty viewing objects at a reading or working distance. An individual with hyperopia may experience blurring, headaches, and eyestrain while performing up-close tasks. A corrective lens can correct this condition by causing the light rays to come to a focus on the retina.

Astigmatism is a refractive error that causes distorted and blurred vision for both near and far objects. A normal cornea has a round or spherical shape and is smooth. With astigmatism, the cornea is curved into an oval shape. This causes the light rays to focus on two different points on the retina, instead of just one, resulting in distorted and blurred vision. Astigmatism often occurs in combination with myopia or hyperopia and can be corrected with corrective lenses.

In most people, a decrease in the elasticity of the lens of the eye begins to occur after age 40 years. This condition, presbyopia, results in a decreased ability to focus clearly on close objects.

If a defect in visual acuity is detected, the patient is referred to an eye specialist for further evaluation. Several types of specialists are involved in the care of the eyes. An ophthalmologist is a physician who specializes in diagnosing and treating diseases and disorders of the eye. An ophthalmologist is qualified to prescribe ophthalmic and systemic medications and to perform eye surgery. An optometrist is a licensed primary health care provider who has expertise in measuring visual acuity and prescribing corrective lenses for the treatment of refractive errors. An optometrist also is qualified to diagnose and treat disorders and diseases of the eye and to prescribe ophthalmic medications. An optometrist is not a physician and is not permitted to prescribe systemic medications or to perform eye surgery. An optician is a professional who interprets and fills prescriptions for eyeglasses and contact lenses.

Assessment of Distance Visual Acuity (DVA)

Myopia can be diagnosed (in combination with other tests) by a distance visual acuity test. In the medical office, the Snellen eye chart is most often used. Two types of charts are commonly used. One type is used for school-age children and adults and consists of a chart of letters in decreasing sizes (Figure 21-2). The other type is used for preschool children, non–English-speaking people, and nonreaders; it is composed of the capital letter E in decreasing sizes and arranged in different directions (Figure 21-3). Visual acuity charts with pictures of familiar objects also are available for use with preschool children. Testing with these charts tends to be less accurate than with the Snellen charts. Some children are unable to identify the objects because of lack of recognition, not because of a defect in visual acuity. It is suggested that the Snellen Big E chart be used with preschool children.

Figure 21-2 Snellen eye chart consisting of letters in decreasing sizes; this chart is used to measure distance visual acuity.

Conducting a Snellen Test

The visual acuity test should be performed in a well-lit room that is free of distractions. The test is usually performed at a distance of 20 feet; this can be conveniently marked off in the medical office with paint or a piece of tape so that it does not have to be remeasured every time the test is performed.

Two numbers, separated by a line, appear at the side of each row of letters on the chart. The number above the line represents the distance (in feet) at which the test is conducted. It is usually 20 feet because most eye tests are conducted at this distance. The number below the line represents the distance from which a person with normal visual acuity can read the row of letters. The line marked 20/20 indicates normal distance visual acuity, or 20/20 vision. This means a person could read what he or she was supposed to read at a distance of 20 feet.

A visual acuity reading of 20/30 means this was the smallest line that the individual could read at a distance of 20 feet. People with normal acuity would be able to read this line at a distance of 30 feet.

A visual acuity reading of 20/15 means this was the smallest line that the individual could read at a distance of 20 feet. It indicates above-average acuity for distance vision. People with normal acuity would be able to read this line at 15 feet.

The acuity of each eye should be measured separately, traditionally beginning with the right eye. Most physicians prefer that the patient wear his or her contact lenses or glasses, except reading glasses, during the test; the medical assistant should record in the patient’s chart that corrective lenses were worn by the patient during the test. An eye occluder should be held over the eye not being tested. The patient’s hand should not be used to cover the eye because this may encourage peeking through the fingers, especially in the case of children. The patient should be instructed to leave open the eye not being tested because closing it causes squinting of the eye that is being tested. The procedure for measuring distance visual acuity is outlined in Procedure 21-1.

Procedure 21-1 Assessing Distance Visual Acuity—Snellen Chart

Outcome

Assess distance visual acuity.

1. Procedural Step. Sanitize your hands.

2. Procedural Step. Assemble the equipment. Perform the test in a well-lit room that is free of distractions. Wipe the eye occluder with an antiseptic wipe, and allow it to dry completely.

Principle. The eye occluder should be disinfected before use.

3. Procedural Step. Greet the patient and introduce yourself. Identify the patient and explain the procedure. Tell the patient that he or she will be asked to read several lines of letters. The patient should not have an opportunity to study or memorize the letters before beginning the test.

4. Procedural Step. Determine whether the patient wears contact lenses or glasses (other than reading glasses). If the patient wears such aids, he or she should be told to keep them on during the test.

5. Procedural Step. Ask the patient to stand on the marked line located 20 feet from the chart.

6. Procedural Step. Position the center of the Snellen chart at the patient’s eye level. Stand next to the chart during the test to indicate to the patient the line to be identified.

Principle. Ensure that the chart is at the patient’s eye level rather than at your eye level, to provide the most accurate results.

7. Procedural Step. Test the acuity of each eye separately. Measure the visual acuity of the right eye first.

Principle. The medical assistant should establish a pattern of beginning with the same eye (traditionally the right eye) every time the test is performed. This helps to reduce errors during the recording of results.

8. Procedural Step. Ask the patient to cover the left eye with the eye occluder. If the patient wears eyeglasses, tell him or her to place the occluder in front of the glasses gently to prevent the glasses from being moved out of their normal position. Instruct the patient to keep the left eye open. During the test, the medical assistant should check to make sure the patient is keeping the left eye open.

Principle. Eyeglasses moved out of normal position may lead to inaccurate test results. Keeping the left eye open prevents squinting of the right eye, which temporarily improves vision, leading to inaccurate test results.

9. Procedural Step. Instruct the patient not to squint during the test because squinting temporarily improves vision. Ask the patient to identify orally one line at a time on the Snellen chart, starting with the 20/70 line (or a line that is several lines above the 20/20 line).

Principle. It is best to start at a line above the 20/20 line to give the patient a chance to gain confidence and to become familiar with the test procedure.

10. Procedural Step. If the patient is able to read the 20/70 line, proceed down the chart until reaching the smallest line of letters the patient can read. If the patient is unable to read the 20/70 line, proceed up the chart until the smallest line of letters the patient can read is reached.

11. Procedural Step. While the patient is reading the letters, observe him or her for unusual symptoms, such as squinting, tilting of the head, or watering of the eyes.

Principle. These symptoms may indicate that the patient is having difficulty identifying the letters.

12. Procedural Step. On a small piece of paper, jot down the numbers that are displayed next to the smallest line of letters that the patient is able to read. If one or two letters are missed, record the visual acuity with a minus sign next to the bottom number, along with the number of letters missed. If more than two letters are missed, the previous line is recorded.

13. Procedural Step. Ask the patient to cover the right eye with the eye occluder and to keep the right eye open. Measure the visual acuity in the left eye as described in steps 9 through 12. During the test, check to make sure the patient is keeping the right eye open.

Principle. Keeping the right eye open prevents squinting of the left eye.

14. Procedural Step. Chart the procedure. Include the date and time, the name of the test (Snellen test), the visual acuity results, and any unusual symptoms the patient exhibited during the test. Also chart whether the patient was wearing corrective lenses during the test. Use the following abbreviations: without correction or with correction. Latin abbreviations are used to record visual acuity. The abbreviation for the right eye is OD (oculus dexter), the abbreviation for the left eye is OS (oculus sinister), and the abbreviation for both eyes is OU (oculus uterque).

15. Procedural Step. Disinfect the eye occluder with an antiseptic wipe, and sanitize your hands.

Assessing Distance Visual Acuity in Preschool Children

With minor variations, Procedure 21-1 can be used to test distance visual acuity in preschool children. The Snellen Big E chart is used for this purpose.

A child needs a complete and thorough explanation of what is expected of him or her before beginning the test. Tell the child you will be playing a pointing game. Do not force the child to play the game because the results then tend to be inaccurate. Draw the capital letter E on an index card, and teach the child to point in the direction of the open part of the E by turning the card in different directions (up, down, to the right, and to the left). Using such phrases as “fingers” or the “legs of the table” to describe the open part of the E helps the child understand what is expected (Figure 21-4). Allow the child to practice the pointing game with the index card until you are sure this level of skill has been mastered. Be sure to praise the child when the correct response is given.