Double vision

Double vision, also called diplopia, means seeing two images of one object. They may appear side by side, one above the other, at an angle, or overlapping.

It can result from a problem within one eye or from the eyes not pointing in the same direction. Causes range from dry eyes and outdated glasses to conditions affecting the eye muscles, nerves, or brain.

Sudden double vision needs same-day medical assessment because some causes require prompt treatment, although a serious cause is not always present.

You may see a clear image with a second sharp, blurred, faint, or shadow-like image. Double vision may be constant or intermittent and can be more noticeable when tired, reading, looking far away, or looking in a particular direction.

Check whether it remains when you cover one eye at a time:

• Monocular double vision remains when the affected eye is open and the other is covered
• Binocular double vision disappears when either eye is covered

Monocular double vision usually comes from a problem within one eye, such as dryness or an irregular focusing surface. Binocular double vision usually means the eyes are not aligned.

Tell a healthcare professional about eyelid drooping, eye pain, headache, weakness, numbness, dizziness, speech problems, or difficulty walking.

Common causes of monocular double vision include dry eyes, astigmatism, cataracts, and changes in the cornea, the clear front surface of the eye. These may cause ghosting rather than two separate images.

Binocular double vision can occur when a tendency for the eyes to drift becomes harder to control because of tiredness, illness, or age-related changes. A childhood squint, or strabismus, may return in adulthood.

Problems affecting the nerves that control eye movement can also cause binocular double vision. Some occur in people with diabetes or high blood pressure.

Other causes include thyroid eye disease, inflammation around the eye, and myasthenia gravis, which causes muscle weakness. Migraine may cause visual disturbances, but these are not always true double vision.

Urgent causes include stroke, bleeding or pressure around the brain, an aneurysm, and head or eye-socket injuries. These are less common, but sudden symptoms require prompt assessment.

Arrange same-day urgent medical assessment if double vision begins suddenly, even if you otherwise feel well. Do not drive yourself while your vision is doubled.

Call emergency services if sudden double vision occurs with:

• Facial drooping, arm or leg weakness, numbness, or speech difficulty
• Severe imbalance, confusion, fainting, or reduced alertness
• A sudden, unusually severe headache
• A newly enlarged pupil or marked eyelid drooping
• Significant head or eye injury
• Sudden loss of vision

Seek same-day care for double vision with a new headache, scalp tenderness, or jaw pain while chewing, particularly if you are over 50. These symptoms may indicate inflammation of blood vessels supplying the eye.

Book a routine appointment if double vision develops gradually, returns, or does not clear. Also seek assessment for a new eye turn, persistent ghosting in one eye, or difficulty with tasks such as reading.

Children with suspected double vision or a new eye turn should be assessed promptly, even if they cannot describe their symptoms.

A healthcare professional will ask when symptoms started, whether they are constant, and whether covering either eye makes them disappear. They may ask about injuries, headaches, neurological symptoms, medical conditions, and medicines.

An eye examination may check vision, pupils, eyelids, eye alignment, and eye movements. A general examination may include strength, balance, sensation, speech, blood pressure, and blood sugar checks.

Depending on the findings, you may need blood tests or scans of the brain, eye sockets, or blood vessels. Not everyone with double vision needs imaging.

Treatment depends on whether the cause is within one eye, eye misalignment, or another medical condition.

Dry-eye treatment or updated glasses may help monocular double vision. Cataracts and corneal problems may require assessment by an eye specialist.

Binocular double vision may be managed with prism lenses, which help the images line up. Some people need treatment for an underlying condition, exercises for selected alignment problems, or surgery. Nerve-related problems may improve over weeks or months but still require assessment.

Until you have been assessed:

• Do not drive, cycle in traffic, or operate machinery
• Move carefully on stairs and uneven ground
• Covering one eye may temporarily stop binocular double vision
• Do not patch a child’s eye unless an eye professional recommends it

Covering an eye relieves the symptom but does not treat the cause. It also reduces depth perception, so take extra care.

Duration depends on the cause. Dryness-related ghosting may change with blinking or improve with treatment. Alignment problems may be intermittent or ongoing. Some nerve-related causes recover over weeks or months; others need longer-term treatment.

Follow-up may involve an optometrist, ophthalmologist, neurologist, or another specialist.

Seek another assessment if double vision worsens, changes pattern, or occurs with new pain, weakness, speech difficulty, pupil changes, or loss of vision.

Can tiredness cause double vision?

Tiredness can make an eye-alignment problem harder to control. However, do not assume new double vision is caused by fatigue, especially if it starts suddenly.

Is double vision always a problem with both eyes?

No. Double vision that remains in one uncovered eye often comes from that eye’s surface or focusing structures. Double vision that stops when either eye is covered usually involves eye alignment.

Can I drive with double vision?

Do not drive while your vision is doubled. It affects distance judgment and your ability to track traffic safely. Follow local licensing requirements and ask the assessing professional when driving may be safe again.

Will an eye patch fix it?

Covering one eye may temporarily stop binocular double vision, but it does not correct the cause. Children should not use an eye patch without professional advice.