Diplopia (Double Vision) Workup

Updated: May 21, 2019
  • Author: Jitander Dudee, MD, MA(Cantab), FACS, FRCOphth; Chief Editor: Andrew G Lee, MD  more...
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Workup

Laboratory Studies

Perform laboratory studies as indicated by aspects disclosed after a comprehensive history and physical examination with emphasis on ocular findings and neurologic screening. Laboratory studies may include anti-acetylcholine (ACh) antibody, anti–striated muscle antibody, anti–muscle-specific receptor tyrosine kinase (MuSK) antibody, low-density lipoprotein receptor-related protein 4 (LRP4) antibody, thyroid-stimulating hormone (TSH), free T4, thyroperoxidase antibody, and thyroid-stimulating hormone receptor antibody.

The absence of antibodies does not rule out disease, and further testing may be elicited to rule out disease. About 9% of patients with myasthenia gravis are seronegative. [8]

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Imaging Studies

Order CT scan or MRI (with contrast) of the skull and orbits to rule out intracranial masses or other pathologic processes, such as the following [9] :

  • A blow-out fracture requires imaging of the orbital floor.
  • Enlarged muscles due to thyroid ophthalmopathy.
  • Tumor of orbit
  • Tumor along cranial nerve pathway
  • Increased intracranial pressure can account for bilateral abducens palsy.
  • Aneurysm of intracranial carotid artery
  • Carotid cavernous fistula: Angiography may be required to confirm the presence of a low-flow fistula.
  • Disease of sinuses (eg, infection, tumor) or bony disorders (eg, dysostoses, encephalocele) can account for displacement of the eye.

Traditional guidelines for imaging patients with new-onset diplopia include imaging all patients younger than 50 years with other neurologic findings, with a progressive course of diplopia, or with a history of cancer. [10] For patients older than 50 years with vasculopathic risk factors, imaging is not always necessary during the initial evaluation. Physicians should conduct a careful review of the patients' history to determine if imaging is medically indicated.

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Other Tests

Cover-uncover test

The cover-uncover test can be used to detect heterotropias. The subject fixates on an object while one eye is covered. If the uncovered eye adducts, the eye has exotropia; if the uncovered eye abducts, the eye has esotropia; if there is upward movement, it has hypotropia; if there is downward movement, it has hypertropia.

If the patient has tropia, the ocular deviation can be measured with prisms. Prisms of differing strengths can be placed in front of the uncovered eye. Prisms of increasing strengths are tested until there is no longer a deviation noted in the uncovered eye.

Tensilon test

The edrophonium (Tensilon) test can be performed to exclude myasthenia gravis, although it has largely been supplanted in the clinic by safer and less-invasive clinical tests (eg, sleep or rest test, ice test).

Intravenous injection of a short-acting anticholinesterase (ie, 10 mg/mL edrophonium chloride [Tensilon]) should be part of the initial workup of a patient with diplopia. Draw up 1 mL, and establish venous access. Then, inject a test dose of 1 mg intravenously to exclude possible hypersensitivity; if no adverse effect is evident, inject the remaining 9 mg.

The expected (normal) cholinergic response includes salivation; lacrimation; flushing; and a brief, but often quite dramatic, reversal of muscle weakness with temporary correction of diplopia and/or ptosis. Occasionally, an excessive cholinergic response may result in increased vagal tone with serious bradyarrhythmias; atropine (0.5 mg) should be available as an antidote.

Other myopathies (eg, progressive external ophthalmoplegia, myotonia) do not respond to anticholinesterases.

Forced duction test

If a lack of movement of one eye occurs in a given direction, excluding a tethered (or fibrotic) muscle may be helpful. Evaluate whether the globe can be passively moved toward the affected area. Traditionally, a forceps is used (after topical anesthesia) to grasp the limbus, and then the eye can be gently tugged in the desired direction. It may be possible to achieve the same result less traumatically by using a cotton wool bud (soaked in topical anesthetic) to "push" on the limbus in the desired direction.

Lee or Hess screen

This highly specialized test separates the field of vision of the 2 eyes. With one eye, the subject fixates on the corners of a rectangle. The other eye is used to visualize the placement of a marker on the same location. Any overaction or underaction will become evident; when one eye has a weak muscle, it will not move as much as the other eye. However, if that eye is used to fixate, the excessive stimulation required will result in an overshoot of the normal yoke muscle in the opposite eye.

Park three-step test

The Park three-step test can help elucidate which of the 4 extraocular muscles responsible for vertical eye movements are responsible for a vertical diplopia. Although first appearing impossibly complex, this test follows a logical progression to progressively eliminate groups of muscles from the 4 pairs.

First, determine which eye appears higher with the head in a normal position. Then, determine which eye is higher with gaze to the left or to the right (ie, with the head turned to the right and then turned to the left). Lastly, determine which eye is higher with the head tilted left and tilted right. (The patient can also help by commenting about when the diplopia is worse.) Then, answer the questions in the following steps:

  • Step 1: Is the left eye or the right eye higher in primary gaze? This reduces the possibilities of muscles from 4 pairs to 2 pairs. For example, if the right eye is higher, the weakness resides either in the muscles depressing the right eye (right superior oblique muscle and right inferior rectus muscle) or in the elevators of the left eye (left superior rectus muscle and left inferior oblique muscle).

  • Step 2: Is the deviation greater with left head turn or with right head turn? This step reduces the alternatives to only one pair of muscles. If the right eye deviates most when the head is turned to the right (both eyes are turning to the left), then only the right superior oblique muscle or the left superior rectus muscle remains.

  • Step 3: Is the deviation greatest with tilting the head to the left or to the right? Called the Bielschowsky head tilt, it relies on the torsional balancing reflexes provoked by head tilt. The higher eye extorts (because of the inferior oblique muscle), while the lower eye intorts (because of the superior oblique muscle).

By combining steps 1-3, only one muscle remains as the culprit. This test requires a logical analysis and the exclusion of alternative possibilities. However, the astute clinician can greatly simplify this process by recognizing that the superior oblique muscle is by far most likely to be responsible for a vertical diplopia. A head tilt to the same side as the involved muscle exacerbates the problem. A very simple rule of thumb is that "the eye that is highest in adduction looks at the affected muscle."

Single-Fiber Electromyography

Single-fiber electromyography (EMG) can be used to detect myasthenia gravis in seronegative cases with isolated ocular findings. Single-fiber EMG is a highly sensitive test for detecting defects in the neuromuscular junction. An electrode measures the potentials of different muscle fibers that are innervated by the same nerve. In a healthy individual, the action potential will excite the muscle fibers at the same time. If there is pathology, there will be variability in the time of excitation of the muscle fibers. Jitter represents the difference in time between the depolarization of the two muscle fibers and is increased in those with myasthenia gravis. The threshold for an abnormal test result is a jitter value greater than the upper limit of the normal value for the specific muscle or greater than 10% of muscle pairs tested with increased jitter. [11]

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