Diplopia

History of present illness should determine whether diplopia involves one or both eyes, whether diplopia is intermittent or constant, and whether the images are separated vertically, horizontally, or both. Any associated pain is noted, as well as whether it occurs with or without eye movement.

Review of systems should seek symptoms of other cranial nerve dysfunction, such as vision abnormalities (second cranial nerve); numbness of forehead and cheek (fifth cranial nerve); facial weakness (seventh cranial nerve); dizziness, hearing loss, or gait difficulties (eighth cranial nerve); and swallowing or speech difficulties (ninth and twelfth cranial nerves). Other neurologic symptoms, such as weakness and sensory abnormalities, should be sought, noting whether these are intermittent or constant. Nonneurologic symptoms of potential causes are ascertained. They include nausea, vomiting, and diarrhea (botulism); palpitations, heat sensitivity, and weight loss (Graves disease); and difficulty with bladder control (multiple sclerosis).

Past medical history should seek presence of known hypertension, diabetes, or both; atherosclerosis, particularly including cerebrovascular disease; and alcohol use disorder.

Examination begins with a review of vital signs for fever and general appearance for signs of toxicity (eg, prostration, confusion).

Eye examination begins with noting the initial position of the eyes, followed by measuring visual acuity (with correction) in each eye and both together, which also helps determine whether diplopia is monocular or binocular. Eye examination should note presence of proptosis (bulging of one or both eyes), ptosis (eyelid droop), pupillary abnormalities, and disconjugate eye movement and nystagmus (involuntary, rhythmic movement of the eyes) during ocular motility testing. Ophthalmoscopy should be done, particularly noting any abnormalities of the lens (eg, cataract, displacement) and retina (eg, epiretinal membrane).

Ocular motility is tested by having the patient hold the head steady and track the examiner’s finger, which is moved to extreme gaze to the right, left, upward, downward, diagonally to either side, and finally inward toward the patient’s nose (convergence). However, mild paresis of ocular motility sufficient to cause diplopia may escape detection by such examination.

If diplopia occurs in one direction of gaze, the eye that produces each image can be determined by repeating the examination with a red glass placed over one of the patient’s eyes. The image that is more peripheral originates in the paretic eye; ie, if the more peripheral image is red, the red glass is covering the paretic eye. If a red glass is not available, the paretic eye can sometimes be identified by having the patient close each eye. The paretic eye is the eye that when closed eliminates the more peripheral image.

The cover test and cover-uncover test can also be used to determine whether a deviation or strabismus is present with both eyes open (manifest/tropia), or only when one eye is open (latent/phoria). Both tests are done on both eyes. For the cover test, the patient is asked to fixate on an object with both eyes open, and one eye is covered. The other eye is observed for a refixation movement, which would indicate it had previously been misaligned, indicating a manifest deviation or tropia. The cover-uncover test is conducted similarly, except the eye being tested is covered for a few seconds and then the cover is removed. The same eye is observed for a refixation movement, which would indicate a latent deviation or phoria. The patient may also see the object "jumping" with the refixation movement during either test.

The other cranial nerves are tested, and the remainder of the neurologic examination, including strength, sensation, reflexes, cerebellar function, and observation of gait, is completed.

Relevant non-neurophthalmologic components of the examination include palpation of the neck for goiter and inspection of the shins for pretibial myxedema (Graves disease).

The following findings are of particular concern:

• More than one cranial nerve deficit

• Pupillary involvement of any degree

• Any neurologic symptoms or signs besides diplopia

• Pain

• Proptosis

Findings sometimes suggest which cranial nerve is involved.

• Third: Eyelid droop, eye deviated laterally and down, sometimes pupillary dilation

• Fourth: Vertical diplopia worse on downward gaze (patient tilts head to improve vision)

• Sixth: Eye deviated medially, diplopia worse on lateral gaze (patient turns head to improve vision)

Other findings help suggest a cause (see table Some Causes of Binocular Diplopia).

Intermittent diplopia suggests a waxing and waning neurologic disorder, such as myasthenia gravis or multiple sclerosis, or unmasking of a latent phoria (eye deviation). Patients with latent phoria do not have any other neurologic manifestations.

Internuclear ophthalmoplegia (INO) results from a brain stem lesion in the medial longitudinal fasciculus (MLF). INO manifests on horizontal gaze testing with diplopia, weak adduction on the affected side (usually cannot adduct eye past midline), and nystagmus of the contralateral eye. However, the affected eye adducts normally on convergence testing (which does not require an intact MLF).

Pain suggests a compressive lesion or inflammatory disorder.

Patients with monocular diplopia are referred to an ophthalmologist for evaluation of ocular pathology; no other tests are required beforehand.

For binocular diplopia, patients with a unilateral, single cranial nerve palsy, a normal pupillary light response, and no other symptoms or signs can usually be observed without testing for a few weeks. Many cases resolve spontaneously. Ophthalmic evaluation is recommended to monitor the patient and help further delineate the deficit, particularly for a third nerve palsy, because it can also progress to involve the pupil.

Most other patients require neuroimaging with MRI to detect orbital, cranial, or central nervous system (CNS) abnormalities. CT may be substituted if there is concern about a metallic intraocular foreign body or if MRI is otherwise contraindicated or unavailable. Imaging should be done immediately if findings suggest infection, aneurysm, or acute stroke.

Patients with manifestations of Graves disease should have thyroid tests (serum thyroxine [T4] and thyroid-stimulating hormone [TSH] levels). Testing for myasthenia gravis and multiple sclerosis should be strongly considered for patients with intermittent diplopia.