STEPHANIE WEST CONSULTANT OPHTHALMIC SURGEON
Specialist squint, double vision and children’s eye care in Southampton
Double vision: diagnosis, relief and specialist treatment
Double vision can be disorientating and may interfere with reading, walking, working and driving. The first step is to establish whether it comes from eye misalignment, an eye condition or another medical cause.
NHS Consultant • Fellowship trained • Adults and children
Understanding double vision (diplopia)
Double vision, medically known as diplopia, means seeing two images of a single object. It may occur only when both eyes are open, or may persist when one eye is covered. That distinction is important because the causes and treatments can be very different.
What is double vision (diplopia)?
Double vision means seeing two images of one object. The images may be side by side, one above the other, or diagonally separated. It can be constant or intermittent, and may affect near vision, distance vision, or both.
What causes double vision?
Double vision has many possible causes. These include problems with eye alignment, the nerves controlling the eye muscles, the eye muscles themselves, thyroid eye disease, previous eye surgery, trauma, or a longstanding squint that has become symptomatic.
What causes sudden double vision?
Sudden double vision can sometimes reflect a new problem affecting eye movements or the nerves that control them. New-onset diplopia should be assessed promptly, particularly if it is associated with headache, drooping of an eyelid, weakness, numbness, difficulty speaking, or other neurological symptoms.
What causes double vision when both eyes are open?
If double vision disappears when either eye is covered, it is called binocular diplopia. This usually means the eyes are not pointing in exactly the same direction, so each eye is sending a different image to the brain.
What causes double vision in one eye?
If double vision remains when one eye is covered, it is called monocular diplopia. This is usually related to the eye itself rather than eye alignment, and can be associated with optical problems such as the cornea, tear film, lens or refractive error.
What is the most common cause of double vision?
There is no single cause that applies to everyone. The most likely diagnosis depends on whether the double vision is monocular or binocular, whether it started suddenly or gradually, the patient’s age, and whether there are any associated eye or neurological symptoms.
Can cataract surgery cause double vision?
Double vision after cataract surgery is uncommon, but it can occur for several reasons, including a previously compensated eye-alignment problem becoming symptomatic or a change in the way the eyes work together.
How is double vision investigated?
Assessment usually includes a detailed history, vision testing, eye movement examination and measurements of eye alignment. An orthoptic assessment can be particularly helpful in documenting the pattern and size of the deviation.
How is double vision treated?
Treatment depends on the underlying cause and may include glasses, prisms, temporary occlusion, treatment of the underlying condition, botulinum toxin in selected cases, or squint surgery.
When should double vision be assessed urgently?
Seek urgent medical assessment for sudden new double vision, particularly if it is accompanied by severe headache, a new drooping eyelid, a change in pupil size, weakness or numbness, difficulty speaking, unsteadiness, or other new neurological symptoms.
Specialist assessment for double vision
If you have persistent or troublesome double vision, specialist assessment can help identify the pattern and likely cause, determine whether further investigation is needed, and discuss the treatment options most appropriate for you.
Sudden double vision needs prompt assessment
New or sudden-onset double vision should be assessed urgently, especially when accompanied by severe headache, weakness, facial droop, difficulty speaking, unequal pupils, eye pain or other neurological symptoms. Contact your local urgent eye service, NHS 111 or emergency services as appropriate.
What happens when you cover one eye?
Binocular double vision disappears when either eye is covered. It is usually caused by the eyes not pointing in precisely the same direction.
Monocular double vision remains when the unaffected eye is covered and is often related to optical problems within one eye, such as tear-film disturbance, corneal irregularity or cataract.
Why double vision can develop
Decompensated childhood squint
A previously controlled eye misalignment can become symptomatic later in life.
Cranial nerve palsy
A nerve controlling an eye muscle may be affected by vascular, neurological or other causes.
Thyroid eye disease
Restriction or inflammation of the eye muscles can alter alignment.
Myasthenia or muscle disease
Variable weakness can cause changing eyelid or eye movement symptoms.
After eye surgery
Changes after cataract, retinal, orbital or previous squint surgery can reveal or alter imbalance.
Age-related change
Connective tissue and eye muscle pulley changes may cause gradually progressive misalignment.
What happens at the appointment?
Detailed history
When it started, whether it varies, health conditions, medication and earlier eye treatment.
Orthoptic measurements
Eye movements, alignment, binocular function and the pattern of diplopia are mapped.
Eye examination
Vision, pupils, eye health and relevant neurological or orbital signs are assessed.
Immediate symptom relief
A temporary Fresnel prism or occlusion may sometimes help while the cause is investigated.
Further investigation
Blood tests, scans or liaison with another specialist may be recommended when needed.
Personalised plan
Options are explained clearly, including observation, prisms, Botox or surgery.
Helping you achieve comfortable single vision
Treatment depends on the cause, stability and direction of the double vision. Some conditions recover with time, while others benefit from prisms, botulinum toxin or squint surgery.
Where permanent single vision in all directions is not possible, treatment focuses on the positions that matter most for daily life, particularly looking straight ahead and reading.
Can I drive if I have double vision?
You should not drive with uncontrolled double vision. Double vision can make it difficult to judge the position, speed and distance of other vehicles, pedestrians and road markings.
The DVLA lists diplopia as a condition that must be reported. Driving may only resume when the DVLA is satisfied that the double vision is controlled and the relevant visual standards are met.
The DVLA makes the final licensing decision. Please check the latest official guidance and contact the DVLA directly if you are uncertain.
Important
Do not drive while you are seeing two images unless the condition has been formally assessed, appropriately controlled and the DVLA has confirmed that you may drive.
Tell the DVLA
Diplopia is one of the eye conditions that drivers may need to report. Use the official GOV.UK service for the latest requirements.
Control may be possible
Depending on the cause, double vision may be controlled with glasses, prisms, treatment or, in selected Group 1 cases, an agreed occlusion method.
Professional licences differ
Bus and lorry drivers are assessed to stricter Group 2 visual standards. Advice that applies to car drivers may not apply to professional drivers.
Common questions
A prism does not remove the underlying cause, but it can move the images together and provide comfortable single vision. Temporary Fresnel prisms are often useful while symptoms change.
No. The need for imaging depends on the onset, examination findings, age, medical history and suspected cause.
Botulinum toxin can temporarily weaken a selected eye muscle. It may relieve symptoms, predict a surgical result or allow time for recovery in selected cases.
Surgery may be appropriate when the deviation is sufficiently stable and symptoms cannot be managed satisfactorily with prisms or other measures.
Orthoptists specialise in eye movement and binocular vision assessment. Their precise measurements are central to diagnosis, prism prescribing and surgical planning.
Arrange specialist assessment for double vision
Self-referrals, professional referrals and insured patients are welcome.