This diabetic type of cranial mononeuropathy III is a complication of diabetes. It causes double vision and eyelid drooping.

Diabetic third nerve palsy; Pupil-sparing third cranial nerve palsy; Ocular diabetic neuropathy

Mononeuropathy means that only one nerve is damaged. This disorder affects the third cranial nerve in the skull. This is one of the cranial nerves that control eye movement and the pupil of the eye.

This type of damage may occur along with diabetic peripheral neuropathy. Cranial mononeuropathy III is the most common cranial nerve disorder in people with diabetes. It is due to damage to the small blood vessels that feed the nerve.

Cranial mononeuropathy III can also occur in people who don't have diabetes.

Symptoms may include:

• Double vision
• Drooping of one eyelid (ptosis)
• Pain around the eye and forehead
• Change in size of the pupil

Neuropathy often develops within 7 days of onset of pain.

An examination of the eyes will determine whether only the third nerve is affected or if other nerves have also been damaged. Signs may include:

• Eyes that are not aligned
• Pupil reaction that is often normal

Your health care provider will do a complete examination to determine the possible effect on other parts of the nervous system. Depending on the suspected cause, you may need:

• Blood tests
• Tests to look at blood vessels in the brain (cerebral angiogram, CT angiogram, MR angiogram)
• MRI or CT scan of the brain
• Spinal tap (lumbar puncture)

You may need to be referred to a doctor who specializes in vision problems related to the nerves in the eye (neuro-ophthalmologist).

There is no specific treatment to correct the nerve injury.

Treatments to help symptoms may include:

• Close control of blood sugar level
• Eye patch or glasses with prisms to reduce double vision
• Pain medicines
• Antiplatelet therapy
• Surgery to correct eyelid drooping or eyes that are not aligned

Some people may recover without treatment.

Prognosis is good. Many people get better over 3 to 6 months. However, some people have permanent eye muscle weakness.

Complications may include:

• Permanent eyelid drooping
• Permanent vision changes

Call your provider if you have double vision and it does not go away in a few minutes, especially if you also have eyelid drooping.

Controlling your blood sugar level may reduce the risk of developing this disorder.

Brownlee M, Aiello LP, Sun JK, et al. Complications of diabetes mellitus. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 37.

Norse AB. Diplopia. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 17.

Wallenstein J. Brain and cranial nerve disorders. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 91.