What Causes Double Vision and When Is It Serious?

Double vision can come from eye alignment problems, cranial nerve palsies, thyroid eye disease, stroke, aneurysm, myasthenia gravis, trauma, orbital disease, or optical problems in one eye. The first question is whether double vision remains when either eye is covered.

For patients searching online, the most important point is that similar symptoms can have very different causes. Double vision, eye movement problems, drooping eyelid, pupil changes, headache, or neurologic symptoms can be mild or serious depending on timing, severity, one-eye versus both-eyes involvement, and whether vision is changing. A medically trained eye examination is often the difference between treating the right problem and chasing symptoms with the wrong drops.

Monocular double vision persists when one eye is covered and often comes from cornea, lens, tear film, or refractive problems. Binocular double vision disappears when either eye is covered and means the two eyes are not lining up correctly. Binocular diplopia can be benign in some cases, but it can also be neurologic or vascular. Timing, pain, pupil changes, headache, neurologic symptoms, trauma, and vascular risk factors determine urgency.

Go urgently or to the ER for sudden double vision with severe headache, neurologic symptoms, droopy eyelid, unequal pupils, eye pain, trauma, weakness, trouble speaking, dizziness, or new vision loss.

Evaluation includes vision testing, pupil exam, eye movement testing, cover testing, eyelid and orbital exam, optic nerve evaluation, and sometimes blood work, imaging, or neuro-ophthalmology referral.

Treatment depends on the cause and may include prisms, patching for short-term safety, treatment of inflammation or thyroid eye disease, vascular risk management, neurologic evaluation, or surgery in selected stable cases.

Do not drive with uncontrolled double vision. Do not assume sudden binocular double vision is eye strain.