When a child has a squint, parents receive a lot of well-meaning advice. Some of…
Double vision: when to seek immediate treatment
Seeing two images of the same object is a frightening symptom – and rightly so. Diplopia may be caused by trivial and perfectly treatable conditions, but it can also be the first sign of a neurological problem requiring immediate attention. It is not always possible to distinguish between the two at home, but there are criteria that can help you decide how urgently you need to act.
First, a simple test
Cover one eye. If the double vision disappears when you cover either eye, it is binocular diplopia: the problem lies in the coordination between the two eyes. If it persists with one eye covered, it is monocular diplopia, the cause of which usually lies within the eye itself – for example, in the cornea or the lens – and which is generally less urgent.
This observation is useful as a guide, not for diagnosis. Make a note of it and mention it, as it is one of the first questions you will be asked.
When to go to A&E without delay
Go to the A&E department of your nearest hospital immediately if double vision occurs suddenly and is accompanied by any of the following symptoms:
Severe headache, different from your usual headaches or one that comes on suddenly.
A drooping eyelid, especially if accompanied by a pupil that is more dilated than the one in the other eye.
Weakness or loss of sensation in one side of the body, or a drooping corner of the mouth.
Difficulty speaking, articulating or swallowing.
Unsteadiness, severe dizziness or difficulty walking.
Severe eye pain, with a red or bulging eye.
A recent history of head injury.
If you experience any of these signs, do not book an appointment: go straight to A&E. Speed is of the essence.
When to attend a scheduled consultation
When double vision develops gradually, is intermittent or is linked to tiredness, without any of the above signs, a scheduled specialist assessment is required. This applies, amongst other cases, to diplopia that is only noticeable at the end of the day, to diplopia that occurs only when looking in a specific direction, or to diplopia accompanying a pre-existing eye deviation that has worsened.
Similarly, double vision that occurs following cataract surgery, when changing spectacles, or in the context of a pre-existing thyroid disorder, requires investigation, even if it is not urgent.
What is investigated
The assessment includes an examination of eye movement in all gaze positions, measurement of the deviation in each position, an evaluation of the function of each muscle, an examination of the pupils and eyelids, and an examination of the fundus. Depending on the findings, an imaging scan or blood test may be required, and the case may need to be referred to neurology, endocrinology or other specialities.
The aim is not only to relieve the double vision, but also to identify why it has occurred.
What treatment is available?
It depends entirely on the cause. When diplopia is due to a motility disorder, management may involve prisms fitted to spectacles, temporary occlusion to make the acute phase more bearable, botulinum toxin, or surgery on the eye muscles once the condition has stabilised. Many cases of oculomotor paralysis improve spontaneously within the first few months, so surgery is usually considered only after this observation period has elapsed.
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