Double vision (diplopia): causes, treatment and driving

Double vision, or diplopia, means seeing two of the object you are looking at. Newcastle Hospitals NHS Foundation Trust explains that it may be present all the time or only when you look in certain directions or at certain distances, and may develop suddenly or gradually.

It comes in two types. Monocular double vision is present when looking only out of the affected eye, generally seen as a shadow or ghosting. Binocular double vision is present only when looking out of two eyes together, generally seen as two separate or overlapping images, side by side, one above the other or diagonal, and goes away whichever eye is covered.

The NHS says double vision has many possible causes, depending on whether 1 eye or both are affected.

The NHS says to go to an optician or see a GP if you think you or your child might have double vision, even if it comes and goes. Children often cannot tell if they have double vision, so look for narrowing or squinting the eyes, closing or covering 1 eye, turning or tilting the head in unusual ways, or looking at you sideways instead of facing forward.

It says to ask for an urgent GP appointment or get help from NHS 111 if you have eye pain and double vision, or double vision that has started suddenly. Call 999 or go to A&E if you have a severe headache or an enlarged (dilated) pupil with blurred or double vision, or double vision after a head injury.

The NHS says an optician or GP can ask about your symptoms and do some simple, painless eye tests. They may refer you to an eye specialist in hospital for tests and treatment, and an optician can tell you if you need to see a GP instead.

Newcastle Hospitals says that if the double vision is of recent onset and is not improving, the ophthalmologist may suggest further tests to find the cause and you may be referred to another hospital specialist. It names the professionals who may manage double vision as ophthalmologists and orthoptists (specialists in squint, binocular vision and eye movement problems).

The NHS says your eyecare team or GP can advise on the best treatment once they work out the cause. In some cases, simple treatments such as eye exercises, wearing an eye patch or being prescribed glasses or contact lenses may be used. Some conditions that cause double vision require eye surgery.

Newcastle Hospitals describes more options for binocular double vision. It advises waiting several months to monitor any changes. In the short term, options include patching one eye, a Fresnel prism (a thin plastic sheet of tiny prisms stuck to a spectacle lens), and a compensatory head position. Exercises are only useful when double vision is caused by an underlying muscle weakness that affects the ability of the eyes to converge when reading. In the long term, options include botulinum toxin injected into an eye muscle (the effect wears off after about three months), surgery on the eye muscles, permanent prisms built into glasses and optical penalisation, where the lens strength in one eye is changed to blur the vision.

Dudley Group NHS Foundation Trust adds that prisms bend light to shift the position of the second image so that the brain can merge the images, and that before a prism is fixed permanently into glasses the prism strength should remain the same for a period of 6 months.

Newcastle Hospitals says it depends on the cause. Where there has been temporary nerve damage you may notice gradual improvement over weeks or months, with full or only partial recovery. Sometimes double vision is permanent and may be very troublesome.

The trust lists the problems double vision can cause as imbalance and unsteadiness, trouble with stairs, being unable to drive safely, difficulty concentrating or reading, neck and shoulder pain from an unusual head position, and low mood. If it is affecting your daily life, tell your eye care team.

The NHS says you must stop driving and tell the Driver and Vehicle Licensing Agency (DVLA) if you are diagnosed with double vision, and that you can drive again if a doctor tells the DVLA it is safe to do so.

The Dudley Group leaflet says you are not allowed to drive with double vision. You should not drive until the double vision resolves, or it is controlled with prisms, occlusion or surgery, you have adapted well to the treatment and you have notified the DVLA. It adds that group 2 drivers (bus, lorry, coach) are not allowed to drive with occlusion, that you can be fined up to one thousand pounds for not telling the DVLA about a medical condition that affects driving, and that insurance may be invalid if you are in an accident with a condition that could affect your driving.

The NHS says squints are more common in children, but they do not always cause double vision, and that an untreated squint in children under 7 causes a lazy eye instead. Children often cannot tell if they have double vision, so watch for squinting, closing one eye, covering an eye with a hand, tilting the head or looking sideways. If you notice these signs, take your child to an optician or GP.

On the NHS, new double vision is assessed by an optician, GP or urgent eye service, then by a hospital eye clinic with orthoptists. Some people choose a private ophthalmology or orthoptic assessment. In either setting, sudden-onset double vision or double vision with other neurological symptoms needs prompt assessment.