A parent suddenly sees double: which signs mean hospital today

Your father walks into the kitchen and says the clock on the wall has become two clocks. Your mother wakes up, looks at the bedside lamp and sees it twice. Neither of them is in pain, and both say they will wait and see how it looks tomorrow.

Double vision that starts suddenly in an adult is the kind that should not wait for tomorrow. This page sets out why, how to tell in one minute whether it is one eye or both, the signs that mean the emergency department or 999, and what the eye doctor checks. It is written for the grown-up children who get the phone call.

My father suddenly sees double: is it urgent?

Yes, treat it as urgent. The NHS says to contact an urgent service if "you have double vision that has started suddenly", and to call 999 or go to A&E for double vision with a severe headache, an enlarged pupil, or after a head injury. In Malaysia the equivalent is 999 and the emergency department of a hospital. Sudden double vision in an older adult is sometimes the first sign of a problem in the nerves, the brain or the blood vessels, and the cause cannot be told by looking.

The urgency comes from the few causes that cannot wait. The action: do not wait for it to pass. Check the signs in the sections below and move the same day.

Is it double vision in one eye or in both eyes?

Cover one eye and see. The NHS explains the test: if the doubling goes away when either eye is covered, it comes from both eyes working together, called binocular double vision. If it stays when the other eye is covered, only the eye that is open is affected, called monocular double vision.

A clinical review in Continuum puts it the same way: if the double vision resolves when either eye is closed it is binocular and neurological in origin, while monocular double vision suggests a problem with the focus or the front of the eye.

The NHS lists dry eyes, astigmatism, cataracts and keratoconus as typical causes of double vision in a single eye. A Malaysian Family Physician review adds that a pale or uneven red reflex in the affected eye may point to a retinal detachment, which needs urgent referral.

If your parent also sees floaters, flashes or a curtain, read sudden floaters and flashes in a parent: when it means an eye doctor today. The action: note which test result you get. Say it to the doctor on the phone. Even a single-eye problem that starts suddenly needs an eye examination soon.

Which signs with double vision mean the emergency department or 999?

Any of the following, with double vision that came on suddenly, is a reason to go to the emergency department now rather than an eye clinic next week.

• Face drooping on one side, weakness in an arm, or slurred or confused speech. The NHS stroke signs are Face, Arms, Speech, Time to call 999.
• Weakness or numbness down one side of the body, dizziness or a severe headache. The NHS lists these among stroke symptoms.
• A severe headache, or an enlarged pupil, with blurred or double vision. The NHS advises 999 or A&E.
• A drooping upper eyelid together with a pupil that looks bigger than the other. The Continuum review lists a dilated pupil with a third nerve palsy as a red flag needing urgent brain imaging, because a blood vessel bulge pressing on the nerve is one cause.
• Double vision after a knock to the head or face.
• Double vision with loss of sight in either eye, or with trouble speaking.

One line from the NHS is worth repeating: it advises calling 999 even if the signs of a stroke have gone away, if they occurred in the last 24 hours. Symptoms that settle do not mean the danger has settled. The NHS also advises against driving yourself to hospital with stroke signs; ask for an ambulance. The action: call 999 for any item above, and say "sudden double vision" and the other sign on the phone.

What if there is a headache, a sore scalp or jaw pain as well?

Then it is urgent for a different reason. The NHS describes giant cell arteritis, also called temporal arteritis, as inflammation of the arteries at the temples. Its symptoms include severe headaches, tenderness of the temple or scalp, pain in the jaw when eating or talking, and vision problems, including double vision or loss of sight. The NHS says it "is serious and needs urgent treatment" and can lead to "stroke and blindness if not treated quickly".

The Continuum review makes the same point for doctors: a headache with new double vision in an older adult raises concern for temporal arteritis and needs prompt attention. The action: if the headache, the tender scalp or the jaw pain comes with new double vision, go to the emergency department the same day and say you are worried about temporal arteritis.

Why does double vision start suddenly in an older adult?

Because the small muscles that move each eye are driven by three nerves, and those nerves depend on a healthy blood supply and brain. The Continuum review lists palsies of the third, fourth and sixth nerves from reduced blood flow in people with high blood pressure or diabetes, and compression by an aneurysm, a tumour or inflammation. It also lists myasthenia gravis, in which an eyelid droops and tires with use, thyroid and other orbital disease, injury that traps a muscle, and brainstem problems such as a stroke.

Some of these are covered elsewhere on our sister sites. Double vision in an adult is often mechanical rather than a squint, and the oculoplastic surgeon Dr Catherine Chow explains thyroid eye disease and orbital fractures as causes of double vision. If your parent has diabetes, diabetes in the family: eye checks for the child and Atuk covers the regular checks. The action: tell the doctor about high blood pressure, diabetes, thyroid disease and any recent injury.

What does the eye doctor check?

The eye doctor starts with the story: which eye, which direction, whether the doubling is worse in the distance or up close, and whether it comes and goes. The Continuum review stresses that careful history can point to the nerve involved before any test.

Then comes examination of how well each eye moves in every direction, cover testing to find which way the eyes are out of line, and the pupils and eyelids. The NHS describes the first step as a discussion of symptoms and painless eye tests, with referral to a hospital eye specialist if needed.

If there are red flags, the next step is brain imaging, which is why the emergency department often comes first. The NHS lists eye exercises, patches, prescription lenses and surgery as options depending on the cause. The action: expect to be asked many questions, and write the answers down on the way.

What should I do before we go, and what can wait?

Note when it began, whether it is one eye or both, whether it is worse looking in one direction, and whether there is a headache, a drooping lid, weakness or numbness. Bring the medicines, the glasses and any recent test results. A photo of the face and eyes taken now can help the doctor see a droopy lid or an eye that sits out of line.

Double vision that has built up slowly over years, such as an adult squint that was always there, is a different problem. Squint in adults: is it too late to straighten the eye covers that. If it is a child who sees double, when a child says they see double has the version for children. For your parent, new and sudden means today. The action: when in doubt, go. A visit that finds a simple cause costs an afternoon, and that is a fair price for being sure.

Common questions

References

1. NHS · Double vision · www.nhs.uk
2. NHS · Stroke: symptoms · www.nhs.uk
3. NHS · Giant cell arteritis (temporal arteritis) · www.nhs.uk
4. Continuum 2014 · Diagnostic approach to diplopia · pmc.ncbi.nlm.nih.gov
5. Malaysian Family Physician 2010 · The two-minute approach to monocular diplopia · pmc.ncbi.nlm.nih.gov

By Dr Chan Li Yen. General information only. It does not replace a consultation. If you are worried about your child's eyes or vision, please see an eye doctor.