Chapter 7 - The Preliminary Examination PDF

# Chapter 7 - The Preliminary Examination ## After Completing the History After completing the history, the examiner is in a position to make a tentative diagnosis of the patient's problem or problems. During the preliminary examination, the examiner's approach should continue to be problem orient...

# Chapter 7 - The Preliminary Examination ## After Completing the History After completing the history, the examiner is in a position to make a tentative diagnosis of the patient's problem or problems. During the preliminary examination, the examiner's approach should continue to be problem oriented. Problems brought to the examiner's attention during the history should be actively investigated and evaluated. Additional problems should be anticipated. ## The Purpose of the Preliminary Examination The purpose of the preliminary examination is to detect any gross anomaly such as a high refractive error, a binocular vision anomaly, a disturbance of ocular motility, or an ocular or systemic disease. Many of the procedures included in the preliminary examination are observations rather than measurements. These observations show the practitioner what to look for during the refractive examination and the binocular vision Examination. ## Organization of Testing Procedures ### Procedures Making Up the Preliminary Examination The procedures making up the preliminary examination should be organized so that they can be done quickly. There should be a minimum of time lost between procedures. The practitioner should attempt to develop the skill of going quickly from one procedure to the next. The practitioner should work rapidly without giving the patient the impression of being rushed or of not allowing adequate time. Even while working rapidly, the practitioner will find it possible to inform the patient of the purpose of each test. This will make the whole experience an interesting one for the patient. ### Physical Plan The order of testing procedures to some extent depends on the type and location of instrumentation used for each test. Larger pieces of equipment should be located conveniently so that the patient is not required to move from one chair to another several times during the examination. This is an inconvenience for the patient and wastes the practitioner's valuable time. Also, if an instrument is not conveniently located, the practitioner may decide not to use this instrument "unless it is really needed". This applies particularly to visual field-testing equipment. ### Room Arrangement A convenient examination room arrangement is shown. The biomicroscope is located on an arm of the refracting unit, along with the keratometer. For those practitioners who use a tangent screen for visual field screening, the tangent screen can be mounted to the right of the ophthalmic chair. It is only necessary to swing the chair around 90 degrees. Adjust the chair height, if necessary, and begin the testing. The refracting unit light is an effective source of illumination for visual field testing and can be quickly swung into place. ### Order of Testing Procedures The following order of testing procedures is suggested: 1. Visual Acuity Testing 2. Tests of Ocular Motility and Binocular Vision - Cover tests - Corneal reflex test - Near point of convergence test - Near point of accommodation test - Motility tests - Tests of pupillary function - Tests of stereopsis 3. Color Vision Testing 4. Visual Field Screening - Confrontations - Tangent screen or automatic perimetry 5. Tonometry 6. Blood Pressure Measurement 7. External Examination (discussed in Chapter 8) 8. Internal Examination (discussed in Chapter 8) ## Small Equipment Items Visual acuity testing, the cover tests, and some of the motility tests require the use of an occluder. Some of the tests for motility require the use of a penlight. The near point of accommodation and the near point of convergence tests require the use of a millimeter ruler. Some tests (visual acuity at near, near point of accommodation, and cover tests) require the use of a near-point acuity chart. These small pieces of equipment can be kept in a jacket pocket or at another convenient location, so the tests can be performed smoothly and rapidly. A convenient acuity chart for preliminary tests is a reduced Snellen chart glued onto a tongue depressor or onto the plastic paddle shown. ## Visual Acuity Measurement The preliminary examination normally begins with the determination of visual acuity. This is a logical starting point, as any complaints of blurred vision elicited during the history can be confirmed. Patients typically expect the doctor to have them read the "eye chart"! Many patients become visibly annoyed if they have to sit through a number of other tests before they are given an opportunity to read the letters on the eye chart! The height of the 6/60 (20/200) E for various testing distances is: | Distance | Height | |---|---| | 6 m (20ft) | 87 mm | | 5 m (16ft) | 73 mm | | 4 m (13ft) | 58 mm | | 3 m (10ft) | 44 mm | ## Standard Testing Conditions Visual acuity testing conditions should be as close to standard as possible. There are several reasons for this: 1. If testing conditions are changed from time to time (due to factors such as relocating equipment), a patient's visual acuity findings may not be comparable from one visit to another. 2. In practices containing more than one examination room, a patient's visual acuity obviously should be identical in each room. 3. A patient's visual acuity findings should be identical in offices of different practitioners. 4. A patient's visual acuity may become a legal issue - such as eligibility for a driver's license, a pension, or an insurance claim. Standard conditions for the determination of visual acuity include letter size, testing distance, chart and background illumination, and contrast. ## Letter Size As discussed in Chapter 1, "normal" visual acuity involves the ability to detect a gap subtending an angle of 1 minute of arc. For a 6-m testing distance, the linear height of the gap is equal to 6(tan 1′) = 1.745 mm; for a letter 5 units high (consisting of three strokes and two gaps), the letter height is 5(1.745) = 8.725 mm or, rounding off, 8.7 mm. When calibrating a visual acuity chart, the simplest procedure is to measure the height of the 6/60 (20/200) letter E, which should be 10(8.7) = 87 mm. Projectors are moved closer to or farther from the screen until the correct letter size is achieved. For testing distances shorter than 6 m or 20 feet, the height of the 6/60 (20/200) E is given. ## Testing Distance Because rays of light diverging from a point 6 m from the eye have a vergence of 0.17 D on reaching the eye, "optometric infinity" differs from real infinity by an appreciable amount. When testing distances shorter than 6 m are used, what effect should we expect this to have on visual acuity? As long as letter size is such that a 6/6 (20/20) letter subtends an angle of 5 minutes of arc at the spectacle plane, an emmetrope or an uncorrected hyperope with reasonable facility of accommodation would be expected to have no difficulty clearing up the letters at a distance less than 6 m. However, an uncorrected myope would be expected to have artificially high visual acuity under these circumstances. For example, at a testing distance of 3 m or 10 feet, a 0.33 D myope would be in perfect focus and would likely read at least one more line of letters than at the 6 m distance. Visual acuity for uncorrected (and corrected) myopes becomes a problem for testing distances much closer than 5 m or 16 feet. The effect of testing distance on visual acuity should not be confused with the effect of testing distance on refractive findings. For an acuity chart at 4 m, the vergence of light is 0.25 D for all patients, no matter what the refractive state, so myopes will tend to be underminused and hyperopes will tend to be overplussed. If the testing distance must be less than 20 feet, the use of a mirror system should be considered. ## Illumination Illumination for visual acuity testing, as well as for other examination procedures, can be considered in terms of either illuminance or luminance. Illuminance is the amount of luminous flux incident on a surface per unit area of the surface and can be specified in foot-candles. Luminance is a measure of the luminous flux emitted or reflected per unit area of a source or a reflecting surface as measured per unit area of a light-sensitive surface. For a reflecting surface that can be considered as a perfect diffuser, luminance is equal to illuminance multiplied by the reflection factor of the surface: $B = rE$ ## Measuring Clinical Illumination Levels Long and Woo (1979) discussed the use of a handheld illuminance meter for measuring clinical illumination levels. To measure the illuminance of a surface with a meter of this type, place the base of the meter on or near the surface. The head of the meter should be parallel to the surface, making sure not to block the light reaching the meter. Select the scale having the appropriate sensitivity and read the illuminance directly from the scale. To determine the luminance reflected from the surface, hold the illuminance meter with its head parallel to and about 4 or 5 cm from the surface under consideration. The illuminance reading is regarded as a luminance reading. Long and Woo pointed out that this method of measuring luminance is strictly accurate only for perfect diffusers of unlimited extent. This is usually an adequate approximation for the materials encountered clinically. Woo and Long (1979) published a table listing luminance levels for use in the optometric examination. Their recommended illuminance level of 12 to 20 foot-candles for distance acuity charts corresponds to a luminance level of about 10 to 16 foot-lamberts if a reflectance factor of 0.8 is assumed. Commercially available chart projectors provide luminance levels in excess of this amount when used with a correctly positioned screen. It is necessary to consider not only the luminance of the acuity chart itself, but also the overall room illumination. For a patient having uncorrected myopia, astigmatism, or absolute hyperopia, extremely bright room illumination may decrease pupil size to the point that acuity will be artificially high. Night myopia would be a factor to consider if there were no background illumination at all, but the high luminance level of the acuity chart itself most likely would be sufficient to minimize any effects of night myopia. Woo and Long (1979) pointed out that because visual acuity depends. It is recommended that the room lighting in the vicinity of a projected chart should be kept low. ## Illuminance Levels Recommended for the Optometric Examination | Procedure | Illuminance | |---|---| | External examination of the eye | 100 fc (1100 lux) at the examining chair measured in the plane parallel to and 1 m from the floor | | Observation of pupillary reflexes, ophthalmoscopy, slit-lamp examinations, retinoscopy, keratometry | 5-10 fc (55-110 lux) measured in the plane parallel to and 1 m from the floor | | Distance tests charts | At least 12-20 fc (130-215 lux), assuming a 0.8 reflecting factor | | Near-point cards | Same as distance charts | | Binocular crossed cylinder | 1-2 fc (10-20 lux) | | Addition measurements using the crossed-cylinder grid target | 1 fc (10 lux) | | Color vision testing | Macbeth or daylight lamp at 80 fc (860 lux) | ## Contrast of the Letters on a Projected Chart Contrast of the letters on a projected chart can also be a problem when polarized projector slides are used. To achieve maximum contrast with polarized slides, it is imperative that the line normal to the screen bisect the angle between the projector beam and the patient's line of sight. In setting up a polarized projection system, it is a good idea to use a small mirror to determine the correct angle for the screen. With the projector turned off, the mirror (and the angle of the screen) should be adjusted until the patient sitting in the chair can see the projector. ## Acuity Testing Procedures Distance visual acuity is determined first with no correction and then with the patient's habitual distance correction. Right eye acuity is always taken first, followed by left eye acuity and binocular acuity. Unless there is a reason to believe that visual acuity will not be within normal limits, a recommended procedure. The practitioner should ask the patient to read the smallest row of letters that can be easily seen. Then to read as many letters as possible in the next row and so forth. However, if there is reason to believe the patient is myopic, either on the basis of complaints or because of a myopic correction, the testing should begin with larger letters. Cautions should be taken. The patient should be cautioned not to squint, as this will cause acuity to be erroneously high in uncorrected myopes or astigmats. Acuity is recorded in terms of the smallest complete line of letters identified, the number of letters not identified in the line in question, or the number of letters identified in addition to those in the line in question. To measure visual acuity at 40 cm, the examiner uses a reduced Snellen chart. This is an acuity chart printed on a stiff or plasticized card measuring about 5 × 6 inches and mounted in front of the refractor on a reading rod. The letter heights are such that a 6/6 (20/20) letter subtends an angle of 5 minutes of arc at a distance of 40 cm. Acuity findings taken at 40 cm are comparable to 6-m findings. ## Procedures for Children Amblyopes have poorer acuity if the whole chart is presented than if a single line of letters or a single letter is presented. This is the phenomenon of contour interaction. It is important in testing children's acuity to present a block of five or six lines of letters. Amblyopia may be missed if a visual acuity chart. *** ## The Cover Tests By means of the unilateral cover test (also called the cover-uncover test), the practitioner can determine the presence or absence of a tropia. It is also known as strabismus, or squint. And by means of the alternating cover test, the practitioner can determine whether a phoria or a tropia is present, but cannot differentiate between the two. If the unilateral cover test results in a negative finding, a positive finding on the alternating cover test indicates the presence of a phoria. Because the alternating cover test can interfere with the manifestation of a tropia, it is customary to perform the unilateral cover test first. ### The Unilateral Cover Test While wearing his or her own spectacle correction if any, the patient's attention is called to a letter on the 6-m Snellen chart. To ensure that accommodation is relaxed, the letter should be no larger than one line above the patient's corrected acuity with the worse eye. The patient should be instructed to keep the letter in sharp focus. The practitioner is seated opposite the patient, with his or her head positioned so that it does not block. Sufficient illumination must be directed toward the patient's eyes so that the practitioner can observe any eye movement. The occluder is placed in front of the right eye, held there for about 1 second, and then removed. During this time, the practitioner observes the patient's left eye for any movement. If no tropia exists, the left eye will make no movement, maintaining steady fixation both when the right eye is covered and when it is uncovered. If the right eye is strabismic (deviating either inward or outward), the left eye will maintain fixation when the right eye is covered and when it is uncovered. Before the cover is placed in front of the left eye, a few seconds should be allowed to elapse so that the eyes return to their normal (undissociated, or associated) relationship. The practitioner then covers the patient's left eye. The cover should be held there for about 1 second and then removed. While the cover is in place, the practitioner observes the patient's right eye for any movement. An absence of any movement of the right eye indicates either that there is no tropia or that the left (covered) eye may be strabismic. A movement of the right eye, on covering the left eye, indicates strabismus - an outward movement occurring in esotropia and an inward movement in exotropia. The sequence of movements in right exotropia is shown. The test is repeated several times - first covering the right eye and then the left, but always allowing a few seconds for the eyes to return to their normal relationship before repeating the test. The test should be repeated in a similar manner at 40 cm. The patient should be instructed to fixate a letter no larger than the line above the best acuity line for the worse eye. The patient should be instructed to keep the letter in sharp focus. If the patient is a child, a picture can be used as long as it includes fine detail that will serve as an accommodative stimulus. Objects such as pencil points, penlights, or visual field wands are not satisfactory for the cover test, as they do not serve as accommodative stimuli. ### Unilateral Or Alternating? A tropia may be either unilateral or alternating. In unilateral cover test, one eye is always the deviating eye. In alternating, either eye may deviate. Unless the unilateral cover test is repeated several times, an alternating tropia may be missed. The practitioner may conclude that the tropia is unilateral. Exotropia of relatively recent onset is particularly likely to be alternating. ### Constant Or Intermittent? A tropia may be present at some times and not at others, this is an intermittent tropia. For example, a patient who has intermittent exotropia may be found on one occasion to have right exotropia but on the next time, only a high exophoria. ### Periodic Strabismus If a tropia is found at one testing distance but not at another, the condition is called a periodic tropia. For example, in some cases of accommodative esotropia, the patient may have no strabismus at distance but may have esotropia at near testing. ## The Alternating Cover Test The conditions for the alternating cover test are the same as for the unilateral cover test. The patient wears his or her own spectacle correction, if any, and fixates a small letter on the Snellen chart. The examiner sits facing the patient. The patient is instructed to keep the small letter in sharp focus. The examiner places the occluder in front of the right eye, holds it there for about 1 second, and then quickly places it in front of the left eye. The test is repeated several times, the occluder being held in front of each eye for about 1 second before being quickly moved to the other eye. The examiner observes the eye that has just been uncovered. If the just-uncovered eye turns inward, it indicates that while under cover it deviated outward (exophoria). If the just-uncovered eye turns outward, it obviously deviated inward (esophoria) while under cover. For the 40-cm testing distance, the test is done in exactly the same manner. The patient fixates a small letter on the reduced Snellen chart. In both distance and near testing, there should be sufficient illumination on the patient's face so that the examiner can easily observe eye movements. With practice, the examiner will be able to detect a movement of 3 or 4 Δ. The practitioner may wish to sharpen his or her ability to detect small amounts of movement by using a low-powered square prism. For example, if no movement is observed in the alternating cover test, the examiner can repeat the alternating cover test while placing a 4 Δ prism - first base-in and then base-out - in front of one eye and observing the other eye for movement. When the prism is placed in the base-in position, it will create an esophoria. The eye without the prism should be observed to turn outward on being uncovered. In the base-out position, the prism will create an exophoria. The eye should turn inward on being uncovered. Thus, if equal amounts of esophoric and exophoric movement are found (with the prism base in the two positions), the original diagnosis of orthophoria was correct. However, if the examiner sees little or no esophoric movement in the base-in position, but sees a large amount of exophoric movement in the base-out position, it indicates that the patient is exophoric rather than orthophoric ## Vertical Phoria If the patient has a vertical phoria, each eye will be seen to turn upward or downward just as the cover is removed. Because a phoria is "shared" between the two eyes, if the right eye is observed to turn downward as it is uncovered, the left eye should be observed to turn upward as it is uncovered. This indicates that the right eye, while covered, deviated upward and the left eye deviated downward. This condition could be called either right hyperphoria or left hypophoria. However, by convention, vertical phorias are always labeled in terms of the hyperphoric eye. *** ## Perceived Target Movement A practitioner can enhance his or her ability to detect a small phoria by asking the patient whether the letter on the chart appears to move as the occluder is moved from one eye to the other. If the patient sees any movement, the practitioner. sks whether the movement of the letter is in the same direction or in the direction opposite to the movement of the occluder. Movement in the same direction indicates exophoria. Movement in the opposite direction indicates esophoria. During the alternating cover test, no diplopia as such is experienced. For an exophoric patient, when the occluder is moved from the right eye to the left eye, the image of the object that had been seen previously by the fovea of the left eye is seen by a retinal point to the right of the fovea of the right eye. The object appears to be in the left visual field. This requires a fixation movement to the left, which is the same direction as the movement of the occluder. It should be understood that the patient does not see the fixation target while eye movement takes place. It is only perceived to move because it changes its position from "straight ahead" to where it was seen by the left eye, to "to the left", where it was seen by the right eye. When movement is perceived rather than real. Psychologists refer to it as phi movement. Thus, when a patient is asked to report the direction of movement of the fixation target during the cover test, the procedure is sometimes called the phi movement test. For an esophoric patient, the image of the object that had previously been seen by the fovea of the left eye is seen by a retinal point to the left of the fovea of the right eye. Therefore, the object appears to be in the right visual field. This requires a fixation movement to the right (due to the fact that the target is perceived to move to the right). This is the opposite of the direction of movement of the occluder. When the patient is a child, a useful procedure is to ask the child to point in the direction that the letter is moving. Even preschool children, who would have difficulty with the concepts of "same" and "opposite", often have little difficulty pointing in the direction the letter is moving. If the examiner suspects a vertical phoria, the patient should be asked whether the letter appears to be higher for one eye than for the other, or whether it appears to move diagonally rather than horizontally. If a strabismic patient has harmonious anomalous retinal correspondence, the letter or other fixation object will appear to be in the same position for each eye. For this reason the phi movement test should not be used with strabismic patients. ## Measurement of the Phoria or Angle of Squint The alternating cover test may be used to measure the phoria or the angle of squint by the use of square prisms or a prism bar. Square prisms are easier to handle than the round prisms found in trail lens sets, and they are available in sets ranging from 1 to 20 Δ or more. Prism bars are available in horizontal form for measuring lateral deviations and vertical form for measuring vertical deviations. Whichever form of prism is used, the examiner places the prism in front of one eye and observes the movement of the other eye while performing the alternating cover test. The examiner increases prism power until a reversal is noted. For example, if exo movement is observed prior to the use of prisms, base-in prism power is increased until no movement is noted. It is then further increased until eso movement is noted. Often there will be a range of 2 to 4 Δ of power for which no movement is noted. The prism that neutralizes the phoria or tropia will be the midpoint of the range. ## The Corneal Reflex Test The corneal reflex test is convenient for determining the presence of strabismus at near. It is useful for a child whose results with the unilateral cover test were questionable. In this test, the patient is instructed to watch a penlight or ophthalmoscope bulb that the examiner is holding at a distance of about 40 cm. The examiner observes the corneal reflexes in the patient's eyes while viewing just above the light source with the dominant eye. If no tropia exists, each corneal reflex will be located approximately 0.5 mm nasal to the center of the pupil. This is because the line of sight makes a small angle (about 5 degrees) with the pupillary axis. This angle, measured from the entrance pupil of the eye, is called the angle lambda. Whereas the corneal reflex is normally about 0.5 mm nasal to the center of the pupil, it may be slightly more displaced nasally in some hyperopic eyes, and it may be near the center of the pupil or even displaced temporally in some highly myopic eyes. Several methods are used to evaluate the corneal reflex: ### Hirschberg's Method With Hirschberg's method, in esotropia, the corneal reflex for the deviating eye will be displaced temporally compared with the fixing eye. In exotropia, it will be displaced nasally. The angle of strabismus can be estimated on the basis that each millimeter. ### Krimsky's Method In Krimsky's method, prisms are placed in front of the deviating eye while using the alternating cover test. The prism power is found that will place the corneal reflex in the same position for the deviating eye as for the fixing eye. The procedure presents a problem because a light source is not an adequate stimulus for accommodation. ### The Angle Kappa If the patient responds to the alternating cover test with square prisms or a prism bar with a test object that acts as an accommodative stimulus, Krimsky's test need not be done. ## Near Point of Convergence It is convenient to test for the near point of convergence just after completing the corneal reflex test. As the penlight is slowly brought inward toward the patient's nose, the patient is asked to report when the light "breaks into two". The examiner watches the patient's eyes to determine any loss of convergence not reported by the patient. If one eye turns outward (as shown by an inward movement of the corneal reflex) without the patient reporting diplopia, it is obvious that the patient is suppressing that eye. The expected value of the near point of convergence is approximately 8 cm or less. It is measured from the spectacle plane. If the near point of convergence is found to be in the neighborhood of 12 to 15 cm on repeated testing, the examiner should suspect the convergence insufficiency syndrome. It is important to record the fact that this occurs and in which eye. It is also important to record the distance at which the eye is seen to turn outward. ## Amplitude of Convergence To determine the amplitude of convergence, the near point of convergence must first be specified in terms of the line joining the centers of rotation of the two eyes. Although the center of rotation of the eye is thought to be about 27 mm behind the spectacle plane. As a matter of convenience this distance can be assumed to be 3 cm. The amplitude of convergence is equal to the reciprocal (in meters) of the near point of convergence multiplied by the patient's interpupillary distance in centimeters. For a near point of convergence of 7 cm, measured from the spectacle plane, and an interpupillary distance of 60 mm, the amplitude of convergence would be: $\frac{1}{0.10}(6) = 60 Δ$ ## Near Point of Accommodation The near point of accommodation can be determined monocularly for each eye as well as binocularly, while the patient wears his or her glasses or contact lenses, if any. For monocular determination of the near point of accommodation. The left eye is, occluded, and the patient is asked to keep the 20/20 row of letters on the reduced Snellen chart. The request is to keep the letters in sharp focus as the card is moved closer. The examiner asks the patient to report when this row of letters begins to blur, and remains blurred. When the patient reports a blur, the examiner records the near point of accommodation as the distance (in centimeters) from the test card to the spectacle plane of the eye. The test is repeated with the right eye occluded and is then repeated binocularly. Care should be taken to make sure the near-point card receives sufficient illumination as it approaches the patient's eyes. However, the illumination should not be so bright as to cause unnecessary constriction of the patient's pupils - this will increase the depth of focus and cause the near point of accommodation to be erroneously low. ## Amplitude of Accommodation If the patient's refractive error is corrected. The amplitude of accommodation can be calculated simply by taking the reciprocal of the near point of accommodation, expressed in meters. For a near point of accommodation of 8 cm (as measured from the spectacle plane), the amplitude of accommodation is 12.50 D. When this test is performed while a patient is wearing old glasses or contact lenses, the practitioner does not know whether these lenses adequately correct the patient's refractive error. Therefore, data on the near point of accommodation, taken through the old lenses, should remain in the recording form as near point of accommodation rather than being converted to amplitude of accommodation. ## Ocular Motility Tests Several tests have been devised to investigate the integrity of the extrinsic ocular muscles and their nerves, including the broad H test and the diplopia field test. ### The Broad H Test One of the most useful motility tests is the broad H test. It is designed to test the action of the horizontal rectus muscles (the patient's eyes fixate a penlight as it is moved into the right-hand and left-hand fields) and to test the action of the vertically acting muscles, the vertical recti, and the obliques (the patient follows the penlight as it is moved to the right, then upward and downward. It is while still turned to the right, and to the left, then upward and downward while still turned to the left). The broad H test is interpreted in terms of the fields of action of the six extrinsic muscles. The field of action for a given muscle refers to the field (as the patient faces it) in which that particular muscle has the greatest action. For the right lateral rectus, the field of action is the right-hand field. For the right medial rectus, the field of action is the left-hand field. The opposite applies for the left lateral rectus and left medial rectus. The fields of action of the four vertically acting muscles are based on the muscle planes of each of these muscles. As shown, both the superior and inferior rectus muscles lie in a plane that makes an angle of approximately 23 degrees with the straight-ahead position of the eye. This means that when the right eye is already turned outward approximately 23 degrees, the superior rectus acts as a pure elevator and the inferior rectus acts as a pure depressor. If we ask a patient to direct his or her gaze approximately 23 degrees to the right and then to look upward, any limitation in movement of the right eye is the fault of the superior rectus. Similarly, if there is a limitation in downward movement of the right eye (with gaze directed. The muscle at fault is the inferior rectus. The superior oblique and inferior oblique muscles lie in a plane that makes an angle of approximately 55 degrees from the straight-ahead direction. Therefore, when the eye is already turned inward approximately 55 degrees, the superior oblique acts as a pure depressor, and the inferior oblique acts as a pure elevator. Any limitation of movement when looking first inward approximately 55 degrees and then downward or upward would be due to the superior oblique (downward) or the inferior oblique (upward). When doing the broad H test, it is not necessary to have the patient direct his or her gaze exactly 23 degrees or 55 degrees to the right or to the left. If the gaze is directed about 30 to 40 degrees in each direction, any limitation of movement can be detected. ## Elevators and Depressors A muscle that turns the eye upward when it is already turned to the right is called a right-hand elevator. A muscle that turns the eye downward is called a right-hand depressor. Left-hand elevators and left-hand depressors are similarly defined. As shown, the muscles that act as right-hand elevators are the right superior rectus and the left inferior oblique. Right-hand depressors are the right inferior rectus and the left superior oblique, and so on. In performing the broad H test, the examiner faces the patient. The examiner moves the penlight in the patient's frontoparallel plane. The examiner must watch both eyes as the patient makes the movement: first to the right, then up, then down, and then to the left, then up, then down. Because it is difficult to watch both eyes at once, it is beneficial to perform the test twice, watching the right eye the first time and the left eye the second time. ## The Diplopia Field Test If one eye appears to lag behind in any field of action in the broad H test, the examiner can ask the patient to wear A pair of red/green goggles (the red lens on the right eye) while the broad H test is repeated. The patient is then asked to report whether two lights (one red and one green) are seen in each of the fields of gaze and, if so, to demonstrate how far apart the two lights appear to be. The mnemonic of Maddox may be used in interpreting the diplopia field test. If diplopia occurs in any field of gaze, the muscle at fault is the same-named straight muscle or the cross-named oblique muscle, and the most peripheral image belongs to the lagging eye. ## Tests of Pupillary Function Testing a patient's pupillary function involves the use of the following tests: measurement of pupil size, measurement of direct, consensual, and near reflexes, and the swinging flashlight test. ### Pupil Size The size of each pupil is measured using a millimeter ruler. Smith (tape no. 6) recommended that measurements be made in both a lighted and a semidarkened room, as the pupils may be of equal size in one circumstance and of unequal size in another. If the practitioner routinely uses an ultraviolet lamp, this lamp can be used to measure pupil size in dim illumination. The fluorescence of the crystalline lens, in ultraviolet light, makes the measurement much easier. ### Direct, Consensual, and Near Reflexes To observe and evaluate direct and consensual pupillary reflexes, the patient fixates on a distant object in a semi-darkened room. A penlight is used to illuminate each pupil, taking care to direct the penlight toward the macular area. The direct reflex - the constriction of the pupil of the illuminated eye - is easily seen, but it is often difficult to observe the constriction of the opposite eye, particularly if the patient has dark irises. The level of. room illumination should be sufficient for the examiner to observe the constriction of the pupil of the. To observe the near reflex, the patient (still in semidarkened illumination) is asked to fixate a distant object. Then the patient is asked to fixate a near object such as a row of letters on a near-point card. The test should be repeated two or three times. Again, the room illumination should be sufficient for the examiner to observe the constriction of the pupil. Smith (tape no. 6) recommends that. _Another method, recorded, used if all reflexes are normal, is PERLA - meaning pupils equal, responding to light and accommodation._ ### The Swinging Flashlight Test To conduct the swinging flashlight test, the patient fixates on a distant object in a semidarkened room. The examiner first illuminates the right eye, then the left. The examiner swings the flashlight from one eye to the other. The procedure is repeated several times. The pupil of each eye will be seen to constrict. However, in the presence of a Marcus Gunn pupil. The pupil of the affected eye will dilate slightly when that eye is illuminated. As shown, the pupils of both eyes will dilate when the eye with the Marcus Gunn pupil is illuminated. Because the pupil fails to constrict when illuminated, the condition. Interpretation of the swinging flashlight test is discussed. ## Pupillary Anomalies Many people will be found to have a difference in pupil size between the two eyes sufficient to be detected. This condition is known as essential anisocoria and is of no consequence. Smith (tape no. 6) suggests that when the pupils are found to be of unequal size, the patient should be asked to supply old photographs to help the practitioner determine whether the difference. In his monograph The Pupil, Smith (tape no. 6) describes eight pupillary abnormalities that he believes are the most important. ### Adie's Tonic Pupil Adie's tonic pupil is a unilaterally dilated pupil with little or no