Vertical diplopia requires detailed history, complete exam

Nashville-Vertical diplopia has an extensive differential diagnosis. However, it is im-portant to realize that if the ophthalmologist does an appropriate history and looks for a few key clues, there is rarely a case for which it is necessary to order imaging studies, according to Sean P. Donahue, MD, PhD, associate professor of ophthalmology, Vanderbilt University Medical Center, Nashville.

"The first things to determine are if the vertical diplopia is monocular or binocular, the associated symptoms, and the conditions under which it improves or deteriorates," he said.

Dr. Donahue suggested a number of factors to consider. For example, if the diplopia resolves when one eye is covered, the patient also must be evaluated with the fellow eye covered. If the diplopia resolves with rest, myasthenia gravis is a possibility. If the severity of the diplopia is dependent on posture changes, there may be superior oblique palsy. If the diplopia is worse in the morning, the patient may have thyroid eye disease. When the diplopia improves with blinking, there may be an anterior segment abnormality, usually on the ocular surface, and a condition like dry eye, he suggested.

Superior oblique palsy"The most common cause of vertical diplopia is a superior oblique palsy, which can be congenital, acquired, unilateral, or bilateral," Dr. Donahue said. "A rule that I learned is that all vertical double vision is the result of a superior oblique palsy until proven otherwise; about 80% of patients who present with vertical double vision will have superior oblique palsy. In addition, all superior oblique palsy is bilateral until proven otherwise."

Cases of congenital oblique palsy, he explained, have two presentations: either as torticollis in a pediatric patient or as intermittent vertical double vision as the fusional amplitudes break down as the child becomes an older adult. In this case, the family album is helpful to demonstrate the abnormal head tilt away from the side of the palsy.

"The ophthalmologist will see large vertical fusional amplitudes. In superior oblique palsy, there is typically mild plagiocephaly, a positive three-step test, and torsion with the double Maddox rod test. Torsion may not be apparent in congenital oblique torsion because of remapping in the afferent system with an anomalous correspondence. Torsion, however, may be apparent on the fundus examination," he said.

He emphasized that in most cases of suspected congenital superior oblique palsy the history and the examination are adequate and no work-up is necessary.

To manage a small deviation in an adult, a vertical prism can be tried and then incorporated into the spectacle correction. If the diplopia is incomitant and bothersome, the patients typically need muscle surgery.

"This surgery can be complicated but usually consists of either inferior oblique recession or vertical rectus muscle surgery. These patients typically do extremely well," Dr. Donahue said.

In contrast, in acquired superior oblique palsy, the patients present with a history of sudden-onset vertical double vision that is almost always worse with head tilt; in most cases, there is a history of severe head trauma.

"It is very rare for an isolated superior oblique palsy without other neurologic signs to be present in the absence of trauma," he said. These patients will have a positive three-step test; the hypertropic eye has excyclotorsion not incyclotorsion.

In these patients with a positive history and an examination that is typical, no work-up is needed. If there is progressive double vision with larger fusional amplitudes and nothing to suggest congenital superior oblique palsy, Schwannomas or other tumors must be ruled out, especially those associated with neurofibromatosis, he cautioned.

Forced duction tests should rule out primary or secondary inferior rectus entrapment. When examining for torsion, if the hypertropic eye has incyclotorsion, skew deviation and other brainstem problems are considerations.

In the acute phase of acquired superior oblique palsy, because the deviation is incomitant and changeable, prisms are not helpful. Either patching one eye or putting tape over a spectacle lens is useful, according to Dr. Donahue. When chronic superior oblique palsy stabilizes for at least 6 months, prisms can be used in the spectacle correction if the deviation is small, otherwise, eye muscle surgery is needed.