Intermittent diplopia a diagnostic challenge

Key Points

Salt Lake City-Intermittent diplopia often is not evident during presentation, which makes its diagnosis problematic. In addition, the history-taking process is a challenge because it is unknown whether the diplopia is indeed intermittent or intermittently noticed, induced with activity, or worsened with fatigue.

Kathleen B. Digre, MD, professor of ophthalmology and neurology, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, described how to ferret out this diagnosis.

Symptoms reflective of a more ominous cause of diplopia, such as fever, weakness, headache, or neural symptoms, should be identified, she noted. A neurologic history is important because underlying multiple sclerosis, tumors, cerebral radiation, or an autoimmune disease might help pinpoint the cause of the intermittent diplopia. Examination is also difficult with this type of diplopia because the physician has to trick it into the light of day, she noted.

Dr. Digre discussed both benign and serious causes of intermittent diplopia. The former can occur commonly as a result of dry eye; orbital-related problems, such as superior oblique myokymia and early Graves' disease; nerve-related disorders, such as cyclic oculomotor palsy, an old fourth-nerve palsy, and ocular neuromyotonia with previous radiation; and brain and brain stem factors, such as vergence and divergence insufficiency following trauma, use of numerous medications, convergence spasm, and strabismus.

Serious causes that require a more extensive work-up are Graves' disease, ocular myasthenia gravis, demyelination, ocular neuromyotonia without previous radiation, and pituitary tumors.

She presented some pearls for identifying some of the conditions. Superior oblique myokymia can be identified at the slit lamp by subtle intermittent torsional movements of the superior oblique muscle; this can be very subtle and visible only upon slit lamp examination. Treatments include gabapentin, carbamazepine, and memantine. Surgery, such as tenectomy or superior oblique myectomy, might be warranted in some cases.

Monofixation syndrome, which appears in about 1% of the population, can be present in patients who have had a facultative scotoma. Diplopia is not present unless they "fall out" of the scotoma. The diplopia can be intermittent or continuous as a result of a small concomitant esotropia and is normally present in distance vision. The diplopia can be treated with prism.

Importantly, no additional work-up is needed unless that patient has other neurologic signs or symptoms, Dr. Digre said.