Cyclovertical Heterophoria
Uncorrected cyclovertical heterophorias frequently cause symptoms that prompt patients to seek visual care; yet, many practitioners are uncomfortable managing such deviations. Some reasons for the reluctance to prescribe treatment for cyclovertical heterophorias include a perception that these conditions are more difficult to understand, the occasional difficulty of making an accurate assessment of the direction and magnitude using conventional measurement techniques, and a mistaken belief that treatment is not very successful. This chapter represents a review of the major clinical aspects of cyclovertical heterophoria. It includes definitions, a brief historical review, a description of the expected frequency and diagnosis of cyclodeviations, and a discussion of applicable clinical management techniques.
Background
DEFINITIONS AND TERMINOLOGY
Vertical deviations, which are upward or downward misalignments of the visual axis of one eye from the object of regard,1 are typically measured in prism diopters (Δ) of vertical misalignment. Cyclodeviations are rotations or rotary displacements of the eye about an anteroposterior axis that are measured in degrees of rotation.2 Both lateral and cyclovertical deviations are classified as follows:
Phorias are latent deviations from the relative positions necessary to maintain single binocular vision.3 Latent deviations are held in check by fusional vergence.4
Tropias are manifest deviations from the position of single binocular vision.5
The terminology for recording vertical deviations is hyper for upward deviations and hypo for downward deviations.6 Generally, vertical heterophorias are designated according to the eye that misaligns higher vertically. As a result of this convention, it is customary to speak of hyperphoria, rather than hypophoria. In general, this convention can be followed unless there is a diagnosed pathology causing the vertical deviation. For example, in thyroid eye disease, a hypophoria often results from inferior rectus muscle involvement, and it is more clinically correct to call this deviation a hypophoria of the eye with the involved muscle (because that is the actual deviation) than a hyperphoria of the other eye. In addition, when there is a strabismus, the strabismic eye is recorded. Thus, vertical strabismus is correctly delineated as either a hypertropia or hypotropia.
Current preferred terminology for torsional deviations is excyclophoria and encyclophoria. Excyclophoria is temporalward rotation (outturning) of the top of the vertical meridian of the cornea during dissociation, whereas encyclophoria is latent nasalward rotation (inturning) of the top of the vertical meridian of the cornea.7
HISTORICAL PERSPECTIVE
The clinical importance of considering cyclovertical deviations when managing patients with binocular vision dysfunction has been recognized for many years. For example, the existence of latent hyperphoria has been debated since the early 1930s, and the role of prism adaptation in determining vertical prism corrections has been important in the clinical literature since the 1950s.8 Evaluation of cyclophorias has a similar history. In 1891, Savage reported “insufficiency of the oblique muscles”9 and described detailed treatment for over 300 cases of cyclophoria. Jackson10 agreed with Maddox11 that “in nearly all cases, nonparalytic cyclophoria causes no symptoms and requires no treatment.” Howe12 implied that the small near excyclophoria that he found in about 25% of normal patients was probably not clinically significant. The contrasting opinions of Stevens13 and Savage9 (that cyclophoria plays a large role in binocular visual problems) and Maddox11 (that cyclophoria is of no consequence) suggest that an intermediate view is probably correct.
INCIDENCE
Hyperphoria
Estimates of the incidence of vertical deviations range from 7%14 to 52%.15 Because of the wide range reported in the literature, it is difficult to be certain of the exact incidence; however, based on an average of the results reported in studies over the last 100 years,16 a reasonable estimate of the incidence of vertical deviations in a clinical population is approximately 20%. Probably only about 10% of these (1 to 2 patients per 100) have a type of latent vertical heterophoria that requires prolonged occlusion for diagnosis.
Cyclophoria
Measurement and analysis of cyclophoria include differentiation between real and apparent torsion (rotation) of the eye(s) about the line of sight. In evaluation of cyclophoria, the important torsion is associated with fusional movements (cyclovergence). Average excyclophoria tested with horizontal Maddox rods at 6 m (20 ft) is about 0.752 ± 1.15 degrees.17 The excyclophoria that is usually present at distance increases as convergence increases, but it does not usually change for lateral version movements. Excyclophorias increase on upgaze and decrease on downgaze.18
The significance of an increase in excyclophoria with convergence is a potential change in the astigmatic axis when fixation shifts from distance to near.18 Scobee19 studied 247 patients and found that 77% had a shift in astigmatic axis during near fixation (Table 14.1) and that this shift in axis could be up to 10 degrees. Although a significant percentage of patients have a measurable change in near astigmatic axis, only a small portion will have the combination of sufficient astigmatism along with a large enough change in axis to cause symptoms that justify treatment.
Characteristics
CAUSE
Significant cyclovertical deviations can be caused by optical (anisometropia), orbital, neuromuscular, or innervational factors. Generally, little is known about the exact cause of either vertical phorias or cyclophorias, although a vertical deviation in downgaze often accompanies significant anisometropia and a small amount of excyclophoria is physiologically normal in near downgaze. Increases in excyclophoria on convergence and upgaze20 are probably due to increased inferior oblique innervation through the third nerve nucleus associated with convergence (in the same way that accommodation, convergence, and pupil size are related). Cyclophoria also results from uncorrected oblique astigmatism. Astigmatic cyclophoria is due to perceived inclination of the images of vertical and horizontal lines that are inclined toward the corneal meridians of greatest curvature. Symptoms generally disappear after properly prescribed optical correction.
MOTOR AND SENSORY FUSION
Integration of similar ocular images into a single percept involves separate components of motor and sensory fusion.21 Because vertical heterophorias typically remain the same at distance and near (in the absence of a paretic muscle etiology or anisometropia, either of which can cause a significant change in the vertical deviation in downgaze), the average vertical motor fusion ranges of about 3 degrees are also the same for distance and near.22
Cyclovergence ranges are greater for encyclovergence. For example, Sen, Singh, and Mathur23 found average encyclovergence in the primary position of 5.25 ± 2.73 degrees and average excyclovergence of 4.15 ± 1.86 degrees measured with vertical lines. However, cyclovertical vergence ranges are variable between subjects and for the same subject at different times, depending on the speed of disparity introduction,24 the targets used,25 and the attention of the subject.26
Cyclovergence ranges are greater for encyclovergence. For example, Sen, Singh, and Mathur23 found average encyclovergence in the primary position of 5.25 ± 2.73 degrees and average excyclovergence of 4.15 ± 1.86 degrees measured with vertical lines. However, cyclovertical vergence ranges are variable between subjects and for the same subject at different times, depending on the speed of disparity introduction,24 the targets used,25 and the attention of the subject.26
Table 14.1 NEAR ASTIGMATIC AXIS SHIFT | ||||||||||||||||||
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Subjective measurements of fusion have sensory as well as motor components. The primary difference between cyclofusion and horizontal/vertical fusion is that the sensory component of cyclofusion is large, whereas it is small for horizontal/vertical fusion.27 For example, the motor component to cyclofusion is probably 50% to 60% of the total fusional response required (2.8 to 3.4 degrees for a 5.75-degree torsional disparity),28 depending on the size of the retinal area covered by the test used. Indeed, it is possible to maintain solely sensory cyclofusion without motor cyclovergence.29
SYMPTOMS
As with other ocular conditions, eye-related symptoms of cyclovertical heterophorias can be categorized as ocular, visual, and referred.30 Symptoms are variable, affected by the patient’s mental and general physical state, and are often similar to symptoms of other types of binocular dysfunction. Therefore, in addition to evaluating cyclovertical deviations, we suggest that a thorough examination of the lateral vergence and accommodative systems be carried out.
SYMPTOMS OF CYCLOVERTICAL HETEROPHORIAS
Lose place when reading (pathognomonic symptom)
Eyes tire easily
Skip lines/read same line (pathognomonic symptom)
Slow reading
Burning sensations
Eyestrain
Headaches
Blurring of reading material
Car sickness
Ocular (asthenopic) symptoms are those directly associated with the use of the eyes. Pulling sensations, itching, gritty feelings, and burning are some of the ocular symptoms related to cyclovertical heterophoria. An asthenopic symptom particular to hyperphoria is motion sickness,31 which most frequently manifests as car sickness, although it may even manifest as a dizziness when walking (e.g., through a department store aisle). Visual symptoms—subjective observations such as blurred or double vision—may or may not be associated with ocular symptoms. Visual symptoms particular to cyclovertical heterophoria include loss of place while reading (hyperphoria), tilting or slanting of objects (cyclophoria), and problems when changing fixation from distance to near. Indeed, the visual symptom of loss of place while reading is so pathognomonic of hyperphoria that a patient who reports loss of place or skipping lines while reading should be considered to have a hyperphoria until proven otherwise; in fact, if initial evaluation suggests no significant hyperphoria in a patient with symptoms common to cyclovertical heterophoria, we suggest that it is clinically prudent to investigate more thoroughly before eliminating this very likely cause. Referred symptoms include headaches, nausea, dizziness, and nervousness.
In clinical practice, perhaps 15% to 20% of all patients have symptoms related to cyclovertical deviation. Patients with cyclovertical deviations may not be diagnosed early and may be anxious and apprehensive. This is not unusual, because a psychoneurotic factor has been found in 75% of ophthalmic patients, compared with 50% in general medical practice.32
SIGNS
An observable head tilt is a frequent sign exhibited by patients with cyclovertical deviations. Another sign that may be observed is a change in astigmatic axis from distance to near refraction, which can indicate uncompensated cyclophoria associated with convergence. Corrective measures will be needed if excessive blur or near discomfort is noticed.
A frequent manifestation of cyclovertical deviations is seen when patients appear to have normal muscle balance but have multiple pairs of eyewear, stating that none are right. Careful diagnostic testing may reveal cyclovertical deviations or aniseikonia. When no binocular anomaly is found on conventional testing and
symptoms are still present even after correction of refractive error, diagnostic monocular occlusion can be useful for determining a management strategy for the symptomatic patient who might otherwise be told that nothing is wrong with your eyes.
symptoms are still present even after correction of refractive error, diagnostic monocular occlusion can be useful for determining a management strategy for the symptomatic patient who might otherwise be told that nothing is wrong with your eyes.
Diagnostic Testing
DISSOCIATED TESTING
The principle of dissociated testing is to measure the direction and magnitude of the cyclovertical phoria under conditions where fusion is prevented. Cyclovertical deviations are frequently noncomitant where the hyperdeviation is larger or smaller depending on the direction of gaze. Thus, when examining a patient with a cyclovertical deviation, it is important to assess the vertical component in the primary position, in all fields of gaze (especially downgaze at near—the reading position), and with the patient’s head tilted to the right and left. This will often allow a determination of the muscle involved in causing the vertical phoria and assist in determining management options.
Assessing Vertical Deviation
The three commonly used techniques to assess the vertical deviation are the cover test, Maddox rods, and prism dissociation. It is important that these tests always be done at least in the primary position and downgaze (reading position).
Cover Test
The cover test, which is used routinely in the diagnosis of lateral heterophorias and cyclovertical strabismus, is often of less value for diagnosis of small cyclovertical heterotropias. Because of the often very small nature of cyclovertical eye movements present in patients with heterophorias, even the most experienced observers may not always obtain a valid measure of cyclovertical heterophorias. As a result, Maddox rods are probably the most clinically used test for cyclovertical heterophorias.
Maddox Rod Evaluation for Vertical Phoria and Cyclophoria
Vertical heterophoria: Single maddox rod. When testing for vertical phoria, a vertically aligned Maddox rod is placed before one eye, and the amount of vertical misalignment between the horizontal line (seen by the eye behind the rod) and a light (seen by the fixing eye) is neutralized using a Risley prism. Figure 14.1 shows the technique needed to evaluate a hyperphoria. Because noncomitancy is frequent in cyclovertical deviations, assessment should be made in all fields of gaze (see the three-step test results in Table 14.2).
 ▪ Figure 14.1 Vertical eye alignment can be assessed with a single vertically oriented red Maddox rod and a penlight. With the patient observing the penlight with one eye and the horizontal red streak with the other, vertical prism power is slowly increased using base-down prism over one eye until the streak is reported to be aligned with the light. Changes in prism power should be at a slow, steady rate. |
Table 14.2 THREE-STEP TEST | ||||||||||||||||||||||||||||||||||||||||
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Cyclophoria: Double maddox rod. When testing for cyclophoria, a Maddox rod is placed in front of each eye, a prism is used to dissociate the rods, and the streaks are compared for parallelism. When cyclophoria is present, one image appears rotated. The corresponding Maddox rod can be rotated until the lines are parallel, and the amount and kind of cyclophoria can be read directly from the indicators. For patients with unilateral superior oblique weakness, excyclophoria is generally between 3 and 7 degrees, whereas in bilateral superior oblique weakness, excyclophoria is typically greater than 10 degrees. Care must be taken that the patient’s gaze is in the primary position with no head tilt. Borish26 suggests that the Maddox rod test for cyclophoria be incorporated into the examination between the delayed subjective and ductions at far.
Maddox Double Prism for Cyclophoria
Another useful clinical test for cyclophoria is the Maddox double prism, which is formed by placing two low-power (3 or 4 Δ) prisms base to base. Monocular diplopia results when an eye fixates with the horizontally oriented bases bisecting the pupillary axis. Thus, if a dot target is used, the eye with the double prism sees two dots, the other eye sees one, and three dots appear with both eyes open. The eye not behind the double prism is the eye being tested, so the subject’s attention is directed to the center dot. Figure 14.2 shows the use of a trial frame for a patient with left excyclophoria. Provided the dots are not fused, the amount of cyclophoria can be quantified by rotating the prism until the dots are vertically aligned. Patient responses (especially those of children) are not extremely accurate on this test.
Prism Dissociation
Prism dissociation, an alternative to Maddox rods that is often used for clinical detection and quantification of vertical deviations, is used less often for cyclophorias. When using this technique for assessment of vertical heterophoria, nonfusable targets are dissociated (usually using horizontal prism) and the patient is required to respond when they are aligned vertically. Figure 14.3 shows the technique for prism dissociation evaluation of a patient with a left hyperphoria.
FIXATION DISPARITY TESTING
The principle of fixation disparity testing is to measure the direction and magnitude of the cyclovertical heterophoria under conditions where fusion is present. Because the deviation is measured while the patient is fusing, fixation disparity tests probably correlate best with symptoms of cyclovertical heterophorias, just as they do for horizontal heterophoria.33,34 Both the horizontal and vertical associated phorias should be assessed. Additionally, the effects of small amounts of horizontal prism on the vertical associated phoria should be determined. Typically, the amount of prism required to reduce the perceived vertical misalignment to zero (vertical associated phoria) can be prescribed with confidence that it will resolve the patient’s symptoms; these patients seldom require vision therapy programs after prism prescription. Just as with dissociated measures (e.g., cover test or Maddox rod), fixation disparity testing should be done at distance, near, and in downgaze at near (reading position).
 ▪ Figure 14.2 A: Assessment of cyclophoria with the double 4 Δ prism test can be done using a single dot as a target. B: When using the double 4 Δ prism, the patient will see three dots—two seen by the eye observing through the double prism and one by the other eye. C: The double 4 Δ prism can be used to measure the amount of cyclophoria. With the prism mounted in a trial frame, the patient rotates the prism until the dots are seen aligned; the amount of rotation indicates the amount of cyclophoria. |
 ▪ Figure 14.3 Vertical eye alignment can be assessed with a vertical prism bar (A) or a Risley prism (B). The patient observes a short horizontal line or a diamond, and vertical diplopia is achieved using about 8 Δ of vertical prism. One eye is occluded, and the target is briefly shown at intervals (flashed). The vertical prism power is slowly decreased until the two targets are reported to be in horizontal alignment. Changes in prism power should be at a slow, steady rate. Small amounts of lateral prism (typically 6 to 10 Δ base-in) may be needed to be sure that the targets are not fused as the vertical prism power is reduced. |
Horizontal Testing
It has been observed in some patients that small amounts of lateral prism can assist fusion to such an extent that a vertical associated phoria is reduced to zero35; in these patients, no vertical prism is needed. The reason these small lateral corrections affect the vertical deviation is not precisely known. However, it is prudent to evaluate this effect when there are small vertical associated phorias, generally less than 1.25 Δ. As a rule, patients with vertical deviations that respond to horizontal prism are candidates for horizontal fusional vergence therapy. They rarely require any prism after vision therapy programs are completed.
Vertical Testing
Vertical Associated Phoria
In general, the amount of prism to reduce the fixation disparity to zero can be prescribed with confidence that it will dramatically relieve the patient’s symptoms. Because this measure is so easy to make, this form of fixation disparity testing has become the test of choice for vertical heterophoria and, when used properly, is also useful for the diagnosis of patients with symptomatic cyclophoria. Associated phoria measures can be made at distance using the American Optical (AO) vectographic slide or Turville testing and at near with the Mallett near unit or the Woolf and Wesson Cards (Fig. 14.4).
 ▪ Figure 14.4 Instruments for clinical measurement of fixation disparity curve parameters include the Disparometer (left), the Woolf (center) and Wesson cards (bottom left), the American Optical vectographic adult slide (bottom right), Turville testing, and the Mallett near unit (right). During each of these tests, the majority of the visual field is visible to both eyes and, thus, can be fused. However, a portion of the central field is only visible to one eye or the other, either because of polarized filters or a septum (Turville test). |
A valuable addition to vertical associated phoria evaluation can be used to be certain that the endpoint has been reached. The principle is to align the eyes vertically so that no alteration in ocular alignment is required when the patient blinks. This can be achieved by interposing vertical prism until the nonius lines seem to be stable through the prism. Then have the patient close both eyes for 1 to 2 seconds. When the eyes are again opened, the patient’s task is to notice whether the nonius lines remain exactly aligned or whether one line or the other had to move up or down to become aligned. Repeat the open-close eyes procedure and modify the prism prescription in 0.25 to 0.5 Δ steps until the lines appear stable and aligned at all times. Frequently, small increases in vertical prism from that seen in standard eyes open associated phoria measurement are required to reach the stable endpoint of alignment of the lines immediately after opening the eyes. When the lines remain aligned immediately after the eyes have been opened again, the amount of prism that is in place can be prescribed.
Forced Vergence Fixation Disparity Curves
Forced vergence fixation disparity curves can be generated by measuring the fixation disparity through various amounts of vertical prism. When there is a vertical phoria, these measures are typically not curves, but rather are very frequently linear. As a result, the associated phoria measure described earlier is the clinically used assessment for the majority of patients. Forced vergence curves are useful primarily when contemplating and monitoring a vision therapy program. See Chapter 15 for a more complete description of fixation disparity testing and interpretation.
Cyclofixation Disparity
Turville tests show cyclofixation disparity when the letters make an oblique line as the test is done.36 Fixation disparity tests such as the AO vectographic adult slide and the Mallett distance and near tests show horizontal and vertical fixation disparity and indicate cyclofixation disparity by a tilt of the test targets.37 These tests do not measure the amount of cyclophoria; the amount has to be measured directly by one of the previously described tests. However, a manifest cyclofixation disparity indicates uncompensated cyclophoria; these patients should be questioned closely for symptoms of cyclophoria and treatment instituted as necessary.
OUT OF PHOROPTER TESTING
Probably, the most frequent challenge that clinicians incur when treating patients with cyclovertical deviations comes as a result of the fusion difficulties that many anisometropic patients have. Patients with anisometropic prescriptions of significant power experience induced prism between the two eyes that increases when looking away from the optical center of the lens. This induced prism impedes binocular alignment and becomes especially significant when the anisometropic patient is presbyopic and looks down to use a bifocal. Many times, significant binocular stress occurs in downgaze and failure to account for these anisometropia-induced complications frequently thwarts successful management. Even patients without anisometropia may have a cyclovertical component that manifests more in downgaze, as is common with patients having unilateral or bilateral superior oblique palsies as well as many with thyroid and myasthenic myopathies.
Patients with significant cyclovertical heterophoria in the primary position (through the phoropter) frequently tend to tilt or turn their heads to a position that allows more comfortable binocular vision. Trial frame evaluation in the primary position and in downgaze (reading position) using the best correction will provide essential information about the patient’s habitual binocular status and head position(s). Correction of a coexisting or induced vertical phoria in downgaze often provides considerable symptom relief.
DIAGNOSTIC OCCLUSION
When occlusion relieves the complaint of the patient, the cause of the complaint is usually some handicap to binocular vision.38 Thus, in cases where a definitive diagnosis cannot be determined using the conventional techniques described earlier, a trial period of 24 hours of occlusion of the hyperphoric eye should be used diagnostically to determine the effect on the patient’s symptoms.38 Table 14.3 lists the considerations for determining when to utilize diagnostic occlusion. The occasionally difficult decision concerning which is the hyperphoric eye is based on cover testing (including patient reports of phi phenomena movement), vertical fixation disparity curves, and reports of vertical instability of the horizontal nonius lines on fixation disparity testing. Following occlusion, vertical prism that neutralizes the vertical fixation disparity (associated phoria) can be prescribed, and vertical vergence therapy may also be considered.
Table 14.3 WHEN AND HOW TO USE DIAGNOSTIC OCCLUSION | ||||||||||||||||||||||||||||||||||||
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Differential Diagnosis
The primary issue in determining the indicated treatment is the etiology of the cyclovertical condition. Newly acquired cyclovertical deviations should be considered to have a serious etiology until proven otherwise. Generally, the newly acquired cyclovertical deviation will be noncomitant and it is important to determine which muscle is involved in causing the vertical deviation.
DETERMINING THE MUSCLE INVOLVED IN NONCOMITANCE—THE THREE-STEP TEST
The primary approach to determining what muscle might be involved in a noncomitant cyclovertical deviation is to make measures in all fields of gaze using one or more of the tests described previously. Diagnostic analysis of the findings in all fields of gaze is called the three-step test—named for the three measures that are made. First, determine which eye is misaligned vertically (the hyper eye), then determine whether the hyper increases in right or left gaze, and finally assess whether the hyper increases on right or left head tilt. Table 14.2 indicates expected findings in various fields of gaze for patients with vertical muscle weakness. For example, if there is right inferior rectus involvement, there will be a right hyper that increases on right gaze and on left head tilt (see bold row in Table 14.2).
Superior oblique palsies are relatively common causes of hyperdeviations because it is moderately easy to injure the trochlear nerve (cranial nerve IV). The findings on the three-step test for superior oblique palsies are easy to remember, because they follow a marching cadence: RSO = right, left, right (right hyper increases on left gaze and on right head tilt); LSO = left, right, left (left hyper increases on right gaze and on left head tilt); see Table 14.2 rows 3 and 6 (shaded). However, instead of memorizing the different findings in Table 14.2, the results of the three-step test can also be graphed, which simplifies the diagnosis by eliminating the need to remember the actions of the extraocular muscles.
A GRAPHICAL METHOD OF REPRESENTING THE THREE-STEP TEST
The results of the three-step test can be represented graphically with a diagrammatic representation of the three-step method (Fig. 14.5A), which signifies the examiner’s view of the patient (thus, the image on the left is the patient’s right eye, whereas the image on the right represents the patient’s left eye). The eight cyclovertical muscles are listed in Figure 14.5A in the action field of each respective muscle. To use the graphical method, follow the steps detailed next:
Step 1. Perform the cover test with the patient fixating straight ahead (in primary gaze) and determine if there is a right or left hyperdeviation. If there is a right hyper, circle the depressors of the right eye (RIR, RSO) and the elevators of the left eye (LIO, LSR) (Fig. 14.5B).
Step 2. Perform the cover test again in right and left gaze, determining if the hyperdeviation increases in right or left gaze. If the hyper increases in left gaze, circle the muscles on the patient’s left in each eye (RIO, RSO, LSR, LIR) (Fig. 14.5C).
 ▪ Figure 14.5 A-D: Perform the cover test with the patient fixating in primary gaze (straight ahead) and if there is a right hyper, circle the depressors of the right eye (RIR, RSO) and the elevators of the left eye (LIO, LSR) (B). Perform the cover test determining if the hyperdeviation increases in right or left gaze. If the hyper increases in left gaze, circle the muscles on the patient’s left in each eye (RIO, RSO, LSR, LIR) (C). Determine whether the hyper increases with head tilt to the patient’s right or left shoulder. If the hyper increases with head tilt to the right shoulder, circle the muscles that correspond to head tilt to the patient’s right in each eye (RSR, RSO, LIO, LIR) (D). The muscle that is circled three times is the affected muscle. In this case, where there is a right hyper in primary gaze that increases on left gaze and right head tilt, the diagnosis is a hyperdeviation caused by a right superior oblique weakness. LIO, left inferior oblique; LIR, left inferior rectus; LSO, left superior oblique; LSR, left superior rectus; RIO, right inferior oblique; RIR, right inferior rectus; RSO, right superior oblique; RSR, right superior rectus. |
Step 3. Determine whether the hyper increases with head tilt to the patient’s right or left shoulder by performing the cover test with the patient’s head tilted to the right and then to the left. If the hyper increases with head tilt to the right shoulder, circle the muscles that correspond to head tilt to the patient’s right in each eye (RSR, RSO, LIO, LIR) (Fig. 14.5D).
Diagnosis. The muscle that is circled three times is the affected muscle (Fig. 14.5D). In this case, where there is a right hyper in primary gaze that increases on left gaze and right head tilt, the diagnosis is that the hyperdeviation is caused by a right superior oblique weakness because the RSO is circled three times. This is expected as findings on the three-step test for superior oblique palsies follow a marching cadence: RSO weakness = right, left, right (right hyper increases on left gaze and on right head tilt); refer again to Table 14.2, row 3 (shaded).
Differential diagnosis of acquired conditions is based on reports of recent-onset diplopia, noncomitancy in which the deviation changes in various fields of gaze, visual field defects, and recent onset of coexisting ocular
health conditions such as papilledema or retinal disease (Case 14.1). Patients with such symptoms or findings should be referred for appropriate systemic (e.g., vasculopathic conditions including diabetes or hypertension), endocrine (e.g., thyroid eye disease), or neurologic (e.g., myasthenia) evaluation. Management of the vertical deviation can continue concurrently.
health conditions such as papilledema or retinal disease (Case 14.1). Patients with such symptoms or findings should be referred for appropriate systemic (e.g., vasculopathic conditions including diabetes or hypertension), endocrine (e.g., thyroid eye disease), or neurologic (e.g., myasthenia) evaluation. Management of the vertical deviation can continue concurrently.
Case 14.1 Recent-Onset Vertical Diplopia
An 18-year-old man complained of recent diplopia while reading. The diplopia had developed over the previous 2 months and seemed to be increasing in frequency. At the time of the examination, he also reported occasional diplopia on upgaze. There was an increase in the magnitude and frequency of the diplopia with strenuous exercise. He had been involved in an automobile accident 4 months previously, but denied any dizziness, ataxia, or systemic illness. He also denied taking any medication. He wore no lens correction at the time of the examination.
Examination revealed emmetropia, with 20/15 acuity in each eye. There was no nystagmus. The cover test revealed a 2 Δ left hyperphoria in primary gaze that increased to a 25 Δ left hypertropia in downgaze. Pupillary reactions were normal; there was no afferent pupillary defect. He had 100 seconds of arc of stereopsis at 40 cm (Randot stereograms). Monocular muscle fields were normal, and binocular fields indicated increasing diplopia in downgaze to the right.
Because of the recent development of vertical strabismus, the patient was referred for neurologic evaluation. Examination findings were consistent with those described earlier, and the patient was scheduled for an evaluation of the posterior fossa by magnetic resonance imagining. The study revealed the presence of an Arnold-Chiari type I malformation. Surgery was deferred until the summer, between school years. No lens correction was prescribed.
Patients with long-standing congenital deviations generally do not complain of recent-onset diplopia; reports of diplopia in patients with congenital cyclovertical deviations have typically been present with varying frequency for a number of years. Further, in contrast to the noncomitancies frequently seen in patients with acquired cyclovertical deviations, many patients with congenital cyclovertical heterophorias have comitant deviations. Patients with congenital deviations are treated using the techniques described next.
Treatment
Management of cyclovertical heterophorias follows the same logical sequence as the treatment for lateral heterophorias outlined in Chapter 3 of this book (Table 14.4). The initial management step is to provide clear retinal images by prescribing the optimum lens correction. This is followed by additional optical management, which, for cyclovertical deviations, primarily consists of vertical or horizontal prism or both. At times, added plus lenses also play a role if better fusion is gained at near through a change in alignment or clearer images in the presence of a coexisting accommodative deficiency. Therapeutic occlusion to eliminate diplopia, by blocking one retinal image, is seldom needed for cyclovertical heterophoria. Usually, fusion is well established and only needs to be enhanced. Vision therapy, which can substantially improve alignment and fusion, can be considered when a cooperative patient will comply with the prescribed procedures and prism correction does not totally eliminate the symptoms.
Table 14.4 SEQUENCE OF CONSIDERATIONS FOR MANAGEMENT OF CYCLOVERTICAL HETEROPHORIAS | |||||||
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Surgery, an important part of management of cyclovertical heterotropias, is needed less often by patients with cyclovertical heterophorias. Large amounts of prism can cause significant spatial distortion and are often
uncomfortable to wear because of their weight. As a result, it is reasonable to consider surgical referral for patients with cyclovertical heterophoria when the treatment requires prism correction larger than 15 Δ, or there is a significant noncomitancy.
uncomfortable to wear because of their weight. As a result, it is reasonable to consider surgical referral for patients with cyclovertical heterophoria when the treatment requires prism correction larger than 15 Δ, or there is a significant noncomitancy.
REFRACTIVE CORRECTION
Clear retinal images assist fusion in cyclovertical deviations. As a result, in the presence of hyperphoria, the best lens correction should be determined by retinoscopy and maximum-plus binocular refraction. Refractive treatment for cyclophoria depends on the type of cyclophoria. When there is uncorrected oblique astigmatism, lens correction found by binocular refractive techniques will frequently eliminate symptoms. Compensatory cyclofusion movements to the natural uncorrected image tilt are made to enhance fusion without spectacle lenses; when the proper correction is in place, the image tilt disappears, there is no need for cyclofusional movements, and the symptoms resolve.
However, there are some patients who are more comfortable without correction of oblique astigmatism. These patients may have aniseikonia caused by the correcting cylinder,32 they may be unable to adjust to vertical prism differences on lateral gaze from the new correction,39 or they may have cyclophoria opposite to the cyclophoria created by fusion of the uncorrected images. For these patients, correction of astigmatism forces them to compensate for the cyclophoria, often unsuccessfully40; vision therapy to reduce suppression and increase cyclofusion abilities is often successful.
Cyclophoria associated with convergence may cause a change in the near astigmatism axis (Case 14.2). This can cause clinically significant symptoms if the power of the correcting cylinder is large or there is a substantial axis shift. Binocular refraction at distance will give the best refractive correction. If the near cylinder axis shift, as determined by binocular refraction at near, is enough to cause symptoms, rigid gas permeable (RGP) contact lenses or separate spectacle lens corrections for distance and near may be needed. Careful attention should also be given to correction of associated vertical deviations.
Case 14.2 Symptomatic Cyclophoria
A 35-year-old man had long-standing complaints of headaches over the left eye, eyestrain, and intermittent blurred vision while reading with his glasses. He wore a moderate astigmatic correction. External and internal ocular health was within normal limits. Visual acuity and refraction with cycloplegia were the same as his current correction:
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There was comitant 3 Δ exophoria at 6 m and 40 cm. There was occasional intermittent suppression of the left eye on Worth dot testing, and stereopsis was 40 seconds at 40 cm with Randot circles. Accommodative findings were normal (amplitude = 8 D, lag = +0.25 D, facility = 10 cpm with ±2.00). There was no fixation disparity at 6 m, but the patient reported a torsional disparity of the left eye’s target at 40 cm. Near refraction revealed the following cylinder axes:
OD: 96
OS: 112
Although distance vision was blurred, reading with near axes findings allowed comfortable vision with no blurring. Maddox rod testing revealed a 1-degree excyclophoria at 6 m and an 8-degree excyclophoria at 40 cm.
A reasonable treatment for this patient would be RGP contact lenses, which would provide clear vision at distance and near as torsion would be compensated by the contact lens correction. The patient was not interested in contact lenses; two pairs of glasses were prescribed—one with the distance axes and the other with the near axes. The patient returned for reevaluation after 2 weeks with the new spectacles with no further symptoms.
PRISM
After prescription of the best lens correction, the next logical consideration in the management of patients with a cyclovertical deviation is prism. Decisions concerning prescription of prism for a patient with a cyclovertical heterophoria are often complicated by the different combinations of symptoms and heterophorias that exist. As illustrated in Table 14.5, when a hyperphoric patient is truly asymptomatic, management is frequently deferred (Table 14.5, row 2). However, treatment may be indicated if the patient is asymptomatic because of avoidance of symptom-causing tasks.
Table 14.5 CLINICAL MANAGEMENT OF VERTICAL HETEROPHORIA | ||||||||||||||||||||||||||||||
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Patients who have symptoms and a manifest cyclovertical heterophoria or a vertical fixation disparity (Table 14.5, rows 3 and 4) are generally more easily managed by prescribing prism than by vision therapy. In general, the prism correction that is considered is a vertical prism correction of sufficient amount to relieve the symptoms. However, for certain patients, a horizontal prism prescription will eliminate the vertical associated phoria.35 This type of horizontal correction of vertical deviation is described more completely in the section on fixation disparity.
Patients Needing Different Vertical Prism at Distance and Near
There are two circumstances where different vertical prism at distance and near may be required. The chief occurrence is when a presbyopic patient has anisometropia causing difficulty because of induced vertical deviation; a non-presbyopic patient typically learns to tilt the chin downward (or raise the reading material), keeping vision close to the optical center of the lens and minimizing the amount of prismatic effect, whereas presbyopic patients are required to view much further down the lens to use the reading segment. Because of these factors, the process of bicentric grinding (slab-off), which can be done on single-vision lenses, is much more commonly prescribed for patients needing multifocals, including trifocals and even progressive lenses. An additional obstacle to fusion occurs when there is significant noncomitancy because of ocular muscle weakness, fibrosis, or entrapment. These afflictions often result in significant difference in the deviation in various fields of gaze. Treatment of these, often difficult to manage, patients often requires prism powers that are different at distance and near (and also possibly in right and left gaze). This can be accomplished with slab-off prism, sector Fresnel prism, and/or two pairs of glasses each having a different prism correction; even then, sector occlusion of one portion of the spectacle lens to block off the diplopic image is occasionally called for.
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