Double Trouble: 4 Things to Do in Patients With Diplopia

Brianne N. Hobbs, OD; Erika L. Anderson, OD


November 13, 2019

Tim (not his real name) was on his way to work when he was startled by two blue cars that suddenly appeared near his car. He swerved to avoid a collision and then quickly pulled onto the shoulder of the road. While trying to collect himself, he looked around and realized that he was seeing two of many objects. Panicked, he called his wife, who immediately brought him to the emergency department, where he was rapidly evaluated.

Every case of diplopia must be taken seriously, though not all cases are due to a serious cause. The cause may be something as simple as an incorrect glasses prescription to a complex, life-threatening condition like hemorrhagic stroke. Here are four strategies for evaluating patients with new-onset diplopia, to help you rule out its most serious causes.

1. Is It Really Diplopia?

The first step in evaluating the patient with diplopia is to establish that the patient is truly seeing two separate images. Although this may seem unnecessary, patients will often complain of "double vision" when their vision is actually blurred or distorted.

Astigmatism is a common cause of ghosting, a visual phenomenon characterized by an image appearing smeared or stretched. This is distinct from diplopia. A sudden onset of astigmatism is rare, so if the presentation is acute, astigmatism is unlikely.

Cataracts may also cause ghosting or halos around lights, which some patients may describe as double vision. Although cataracts typically progress slowly, some types have a more rapid progression, causing the patient to become symptomatic relatively quickly.

To determine whether the patient really has diplopia, ask the following questions:

  • Do you see two separate images?

  • If so, how are the images oriented in respect to each other—vertically, diagonally, or horizontally? The answer to this question helps provide additional information about the cause of diplopia (Table).

Table. Some Common Etiologies Associated With Diplopia*

Type of diplopia

Associated cranial nerves

Common etiologies


Cranial nerve III or IV

Ischemia, trauma, thyroid eye disease


Cranial nerve III, IV, and/or VI

Ischemia, aneurysm, trauma, cavernous sinus pathology, neoplasm


Cranial nerve III or VI

Ischemia, internuclear ophthalmoplegia, neoplasm, trauma, convergence insufficiency

*This table is intended to be a summary and is not comprehensive.
  • Does the diplopia go away when one eye is covered? (Always check both eyes.)

    • If the diplopia resolves when either eye is covered, the diplopia is binocular. Evaluation of the lids, pupils, and extraocular muscles in patients with binocular diplopia is necessary to determine the level of urgency and whether a referral to an ophthalmologist or optometrist would be beneficial.

    • If the diplopia persists even when one eye is covered, it is monocular. Referral to an ophthalmologist or optometrist is most appropriate because the diplopia is probably due to an abnormality in the cornea, lens, or vitreous. Monocular diplopia is not an emergency and carries no systemic risk because it usually originates from refractive changes to structures within the eye.

  • Does the diplopia worsen when you look in certain directions?

    • Diplopia that varies in magnitude in specific gazes increases the likelihood of a muscle palsy or a muscle restriction. If the patient notices diplopia that increases substantially when looking up, muscle entrapment due to trauma must be ruled out. Internuclear ophthalmoplegia can cause diplopia in lateral gazes and may be due to demyelinating disease in younger patients or ischemia in older patients.

  • Is the diplopia of sudden onset and constant?

    • A sudden onset of constant diplopia increases the likelihood of an underlying systemic etiology. Isolated cranial nerve palsies often cause a sudden onset of diplopia that does not resolve. Although isolated nerve palsies are not always an emergency, neuroimaging may be appropriate, especially in patients with concurrent vascular disease. Another cause of acute-onset, constant diplopia is a pathology that affects the cavernous sinus and may involve multiple cranial nerves. Facial pain or numbness in addition to constant diplopia should increase suspicion of a cavernous sinus pathology. Proptosis and dilated episcleral and conjunctival blood vessels are additional indicators of cavernous sinus abnormalities.


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