Eye and Ear Assessment and Procedures
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.
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.
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.
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 
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.
The child might need help holding the eye occluder in place. The aid of another person such as the parent would then be required.
Assessment of Near Visual Acuity (NVA)
Near visual acuity testing assesses the patient’s ability to read close objects (i.e., at a reading or working distance); the test results are used to detect hyperopia and presbyopia.
The test is conducted with a card similar to the Snellen eye chart; however, the size of the type ranges from the size of newspaper headlines down to considerably smaller print such as would be found in a telephone directory (Figure 21-5). The test card is available in a variety of forms, such as printed paragraphs, printed words, and pictures.
The test should be performed in a well-lit room free of distractions. It is conducted with the patient holding the test card at a distance between 14 and 16 inches. If the patient wears reading glasses, they should be worn during the test. The acuity should be measured in each eye separately, traditionally beginning with the right eye. An eye occluder should be held over the eye not being tested. The patient should be instructed to keep the covered eye open because closing it may cause squinting of the eye that is being tested. The patient is asked to read or identify orally each line or paragraph of type. During the test, the patient should be observed for unusual symptoms, such as squinting, tilting the head, or watering of the eyes, which may indicate that the patient is having difficulty reading the card. The patient continues until reaching the smallest type that can be read.
The results are recorded as the smallest type that the patient could comfortably read with each eye at the distance at which the card is held (i.e., 14 to 16 inches). The recording is based on the type of test card used to conduct the test. One type of card uses a recording method similar to that used with the Snellen eye test. For this type of near visual acuity card, the results would be recorded as 14/14 for a patient with normal near visual acuity. This means the patient read what was supposed to be read at a distance of 14 inches. Also included in the recording should be the date and time, corrective lenses worn, and any unusual symptoms exhibited by the patient.
Assessment of Color Vision
Defects in color vision may be classified as congenital or acquired. Congenital defects are more common and refer to a color vision deficiency that is inherited and is present at birth. Congenital color vision deficiencies most often affect males. Acquired defects refer to a color vision deficiency that is acquired after birth, resulting from such factors as an eye or brain injury, disease, and certain drugs. Color vision tests, such as the Ishihara test (Figure 21-6), detect congenital color vision disturbances and are commonly performed in the medical office. A basic screening for color vision can be performed by asking the patient to identify the red and green lines on the Snellen eye chart.
What Would You Do? What Would You Not Do?
Nicole Neason brings her daughter, Haley, to the office for a camp physical. Haley has just completed the fourth grade and is going to summer camp for 2 weeks with Tess, her best friend. Tess wears glasses and Haley thinks they are really cool. She often asks to try on Tess’s glasses and wishes she could wear glasses just like her best friend. When Haley is measured for visual acuity, she misses a few letters on the 20/70 line, the 20/50 line, the 20/40 line, and the 20/20 line. She is unable to read any of the letters on the 20/15 line. After the examination, Haley wants to know if she’s missed enough letters to be able to get glasses. 
Ishihara Test
The Ishihara test for color blindness is a convenient and accurate method to detect total congenital color blindness and red-green color blindness by assessing an individual’s ability to perceive primary colors and shades of color. The Ishihara book contains a series of polychromatic plates of primary colored dots arranged to form a numeral against a background of similar dots of contrasting colors (see Figure 21-6). Patients with normal color vision are able to read the appropriate numeral; however, patients with color vision defects read the dots either as not forming a number at all or as forming a number different from the one identified by the individual with normal color vision. The first plate in the Ishihara book is designed to be read correctly by all individuals (with normal vision and exhibiting color vision deficiencies) and should be used to explain the procedure to the patient.
The Ishihara test should be conducted in a quiet room illuminated by natural daylight. If this is not feasible, a room lit with electric light may be used; however, the light should be adjusted to resemble the effect of natural daylight as much as possible. Using light other than just described, such as bright sunlight, may change the appearance of shades of color on the plates, leading to inaccurate test results.
The medical assistant is responsible for performing the color vision test and for recording results in the patient’s chart. The physician assesses the results to determine whether the patient has a deficiency in color vision.
The Ishihara test consists of 14 color plates. Plates 1 through 11 are used to conduct the basic test, and plates 12, 13, and 14 are used to further assess patients who exhibit a red-green color deficiency. It is unnecessary to include these plates (12, 13, and 14) in the test of patients who exhibit normal color vision. In interpreting the results, if 10 or more plates are read correctly, the patient’s color vision is considered normal. If 7 or fewer of the 11 Ishihara plates are read correctly, the patient is identified as having a color vision deficiency. It would be unusual for the medical assistant to obtain results in which the patient has read eight or nine plates correctly. The test is structured so that a patient with a color vision defect generally does not read eight or nine plates correctly and the rest incorrectly.
If a defect in color vision is detected, the patient is referred for additional assessment of color vision to an ophthalmologist or optometrist, who would use more precise color vision tests. The procedure for assessing color vision using the Ishihara color plates is outlined in Procedure 21-2.
Procedure 21-2 Assessing Color Vision—Ishihara Test 
1. Procedural Step. Sanitize your hands. Assemble the equipment.
2. Procedural Step. Conduct the test in a quiet room illuminated by natural daylight.
Principle. Using unnatural light may change the appearance of the shades of color on the plates, leading to inaccurate test results.
3. Procedural Step. Greet the patient and introduce yourself. Identify the patient and explain the procedure. Using the first (practice) plate as an example, instruct the patient to orally identify numbers formed by colored dots. Tell the patient that 3 seconds will be given to identify each plate.
Principle. The first plate is designed to be read correctly by all individuals and is used to explain the procedure to the patient.
4. Procedural Step. Hold the first color plate 30 inches (75 cm) from the patient, at a right angle to the patient’s line of vision. The patient should keep both eyes open during the test.
5. Procedural Step. Ask the patient to identify the number on the plate. If the plate consists of a traceable winding colored line, ask the patient to trace the line using a cotton swab or the eraser end of a pencil. The patient’s finger should not be used to make the tracing.
Principle. The patient’s finger should not be used to trace the line because soiled fingers can degrade the plate over time.
6. Procedural Step. Record results after each plate. Continue until the patient has viewed all the plates. To record color vision results, use the plate identification number and the number given by the patient. If the patient is unable to identify a number, the mark X should be recorded to indicate that the patient could not read the plate. Examples:
Plate 5: 21. This means the patient read the number 21 on plate 5 (instead of 74).
Plate 6: X. This means the patient could not identify a number on plate 6.
Plate 11: Traceable. This means that the patient correctly traced a winding line on plate 11.
As you can see from the results of this patient’s color vision test, the patient correctly identified all 11 plates, which indicates normal color vision. Because the patient has normal color vision, the medical assistant did not need to include plates 12, 13, and 14 in the color vision test.
Principle. Reading 10 or more plates correctly indicates normal color vision. If 7 or fewer of the plates are read correctly, the patient is identified as having a color vision deficiency.
7. Procedural Step. Complete the charting entry. Include the date and time, the name of the test (Ishihara test), and any unusual symptoms the patient exhibited during the test, such as squinting or rubbing the eyes.
8. Procedural Step. Return the Ishihara book to its proper place. The book of color plates must be stored in a closed position to protect it from light.
Principle. Exposing the plates to excessive and unnecessary light results in fading of the color.
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