Double Vision: Causes and When It Is an Emergency
Medically Reviewed by Dr. Pedro Yelamo Vera, MD
Licensed Physician No. 484814280 · Official Medical College of Bizkaia (Spain)Last reviewed: 5 November 2026
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Double vision that starts suddenly is an emergency. It can be caused by a stroke or a problem with the nerves that move the eyes. Call 112 if it comes with weakness, slurred speech, a bad headache or a drooping eyelid. If the double vision is in one eye only, the cause is usually in the eye itself, such as dry eye or a cataract. This guide is by Dr. Pedro Yelamo Vera, a GP licensed in Spain (Colegiado No. 484814280).
- Double vision means seeing two images of one thing.
- Cover one eye. If the double image goes, it comes from both eyes. If it stays, it comes from one eye.
- One-eye double vision often comes from dry eye, astigmatism, cataracts or keratoconus.
- Both-eye double vision is usually a muscle or nerve problem and can be serious in adults.
- If it starts suddenly or after a head injury, go to A&E or call 112.
- Do not drive while you see double.
What is double vision?
It means you see two images of one object, side by side or one above the other. Doctors call it diplopia. It is not the same as blurred vision, where you see one image that is not sharp. In Spain it is visión doble or diplopía.
Is it in one eye or both eyes?
Try this simple test: cover one eye, then the other.
- Both eyes (binocular): the double image goes when you cover either eye. The eyes are not lined up.
- One eye (monocular): you still see double with one eye open. The problem is inside that eye.
What causes double vision in one eye?
- Dry eye: the front of the eye is no longer smooth. It gets better when you blink.
- Astigmatism or glasses that need updating.
- Cataracts.
- Keratoconus, where the front of the eye thins and changes shape.
This is not usually urgent, but get it checked by an optician or an eye doctor (oftalmólogo).
What causes double vision in both eyes?
It happens when the eyes do not move together. In adults it can be a sign of something serious:
- Damage to an eye nerve from diabetes or high blood pressure.
- Thyroid eye disease, which affects the eye muscles.
- Myasthenia gravis, which gets worse at the end of the day and can cause a droopy eyelid.
- A stroke or mini-stroke (TIA).
- A head injury.
- More rarely, an aneurysm, a tumour or multiple sclerosis.
In children, an eye that turns in or out (a squint) needs an eye doctor's check to protect their sight.
Can double vision come and go?
Yes. Being very tired, alcohol or some medicines can cause brief double vision. Even so, if it keeps happening or there is no clear reason, see a doctor. Double vision is not a symptom to wait and watch.
What should I do in the meantime?
- Do not drive or use machines.
- A patch over one eye can ease it, but it does not replace a check.
- Note when it started, whether it changes during the day and any other symptoms.
- Bring your glasses and your list of medicines to the visit.
When is double vision an emergency?
Call 112 or go to A&E (urgencias) if double vision:
- Starts suddenly.
- Comes with a severe headache, or one pupil larger than the other.
- Comes with a drooping eyelid, a drooping face, weakness in an arm or leg, or trouble speaking.
- Starts after a head injury.
- Comes with eye pain, fever or severe dizziness.
If the double vision is in one eye, has been there a while and there are no other symptoms, book an eye doctor.
Frequently asked questions about double vision
Can stress cause double vision?
Tiredness and stress can make your eyes feel strained or blurry, but true double vision needs a cause. Get it checked.
Can glasses fix double vision?
Sometimes, if the cause is your prescription. Glasses with prisms help some cases of both-eye double vision, always after a proper check.
Can diabetes cause double vision?
Yes. It can damage an eye nerve. This often gets better in weeks or months, but other causes must always be ruled out.
Can I drive with double vision?
No. You cannot drive safely while seeing double. Wait until a doctor has checked you.
Can a doctor check double vision by video?
One-eye double vision that has lasted a while can be discussed by video. If it starts suddenly, do not wait: call 112.
Getting a medical assessment
If you are in Spain and you are worried about double vision that did not start suddenly, you can book a video consultation with Dr. Pedro Yelamo Vera, a physician registered in Spain. If it started suddenly, call 112. You can also read about our urgent care service, dry eye and headaches. A prescription is never guaranteed: it is issued only where clinically appropriate after a genuine evaluation, as a private electronic prescription under Spanish law. This service is for urgent, non-emergency care. In an emergency, call 112.
This guide is general information. It does not replace the package leaflet or the advice of your doctor or pharmacist.
Sources
This content is written and reviewed by a licensed physician with reference to the following sources.
