Microvascular cranial nerve palsy (MCNP) is one of the most common causes of double vision in older people. It occurs more often in patients with diabetes and high blood pressure and is often referred to as a “diabetic” palsy.

MCNP occurs when the blood flow is blocked to one or more of the three nerves that control the eye muscles. If the abducens nerve is blocked by improper blood flow, your eye will not be able to move toward the outside, and you will have double vision (see side-by-side images). If the trochlear nerve is affected, you will have vertical double vision (see one image on top of another). And if the oculomotor nerve is affected, you will have limited up and down eye movement. The eyelid may droop, too.

Although it is not clear what blocks the blood flow, diabetes, high blood pressure, or migraines may be to blame. Occasionally, there may be a blocked vessel in the covering of the brain, which can be associated with pain around the eye.

Symptoms of MCNP include weakness in one or more eye muscles, blurred or double vision, drooping eyelid, or enlarged pupil.

Although there is no known treatment for MCNP, double vision may be treated by patching either eye. If the double vision persists, prism eyeglasses or eye muscle surgery may be prescribed. Sometimes, anti-inflammatory drugs such as ibuprofen may help with any pain associated with MCNP.

Over a period of six to 12 weeks, normal function and vision should return. Your nerves will not be permanently injured. However, if the double vision does not go away, it is important to tell your ophthalmologist (Eye M.D.).

(c) 2007 The American Academy of Ophthalmology