Diagnosis[ edit ] Diplopia is diagnosed mainly by information from the patient. Doctors may use blood tests, physical examinations, computed tomography CT , or magnetic resonance imaging MRI to find the underlying cause. That involves blocking one eye to see which symptoms are evident in each eye alone. In such a case while the fovea of one eye is directed at the object of regard, the fovea of the other is directed elsewhere, and the image of the object of regard falls on an extrafoveal area of the retina. The brain calculates the visual direction of an object based upon the position of its image relative to the fovea. Images falling on the fovea are seen as being directly ahead, while those falling on retina outside the fovea may be seen as above, below, right, or left of straight ahead depending upon the area of retina stimulated.
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III Presentation Diplopia presents either with a complaint of double vision or the observation of squint. Paralysis of a muscle means that the eye will not move fully in the direction in which it pulls. At rest, when the other muscles are unopposed, the eye may therefore deviate in the opposite direction from the pull of the affected muscle.
Diplopia may occur alone or in conjunction with other symptoms such as pain on eye movement, pain around the eyes, ptosis, headache or nausea. Symptoms The patient will often complain of double vision. Images may overlap or be adjacent. It is helpful to ask about image alignment, whether they appear or worsen on particular direction of gaze, and whether they are intermittent or constant.
It is also helpful to find out if the double vision disappears on closing one eye, and whether both images are in focus.
There may be associated symptoms such as ptosis, eye pain with or without eye movement , headache and nausea. It suggests this is the affected side, as eyelid elevation is partly controlled by the oculomotor nerve III. Check the pupils and whether both are equal and react to light and accommodation. Pupil abnormalities might otherwise signal that the cause lies inside the bony skull. Visual acuity should be measured in each eye and may point to intraorbital problems, including retractive errors.
Fundoscopy should be performed to rule out papilloedema. Attempt to identify which eye is affected and which direction of gaze is limited. This will allow determination of which structures are likely to be involved. Examine the alignment of the eyes in various head positions and on looking in every direction. Note whether one eye seems to be deviated.
Isolated palsy of only one of the muscles supplied by the oculomotor nerve is unusual. Hold the head still with one hand and hold up the index finger of the other hand about cm from the eyes. Ask the patient to follow your finger to the left and the right and up and down, and to note when diplopia occurs. If it is not clear that one eye is failing to move as far as the other, repeat the test but, instead of getting the patient to follow a finger, shine the light from a pen torch directly at their eyes.
The light should be reflected in the centre of the pupil. When diplopia occurs the reflection will appear eccentric in the pupil on the affected side. Children In children, especially very small children, getting the child to follow a pen torch is much easier than asking the child to follow your finger and to report diplopia. The cover test may also be helpful.
Ask the child to look at your face and then quickly cover one of their eyes. If there is a squint, the eye with the pathology will move to look directly at you only when the other is covered. From the history and examination it should be possible to decide which muscle or muscles are affected, or whether the cause is within the globe.
In primary disorders of muscle where fatiguability is the prime feature, examination may fail to show any abnormality. Common causes The intracranial course of the abducent nerve VI is long and so it is vulnerable at many sites.
Hence, abducent nerve paralysis is important but it is a poor localising sign for a space-occupying lesion. Isolated abducent nerve palsy is relatively common, occurring particularly in patients with vasculopathies such as diabetes. Diplopia can be psychosomatic. This is suggested by inconsistency of history and unusual elements such as monocular double vision in both eyes, but it is nevertheless a diagnosis of exclusion.
Drug and alcohol intoxication may cause temporary diplopia. There will usually be other suggestive features. Tiredness may cause abnormalities of eye muscle movement. Convergence insufficiency is more marked when a person is tired. Transient diplopia may occur with tiredness, particularly if reading glasses are needed but absent or inadequate. Diagnosis is usually on the history but it is important to exclude other causes of muscle fatiguability.
This is, however, a condition of very low incidence. It may affect both eyes equally or unequally. Other rare conditions of muscle may also affect eye movements, including myotonic dystrophy. Fluctuating weakness of external ocular muscles can occur in encephalopathy and sepsis. There will normally be confusion and other signs of severe illness. Vertical gaze palsy is the inability to look up or down.
It affects both eyes. Pupils are often unequal but fixed and there is usually no diplopia. Inability to look down can lead to falling down stairs. Diplopia can occur. Rare causes Ophthalmoplegic migraine is a rare condition consisting of headaches accompanied by weakness of the external ocular muscles.
The condition may represent a variant of migraine, although clinical presentation and MRI findings have also suggested that it might be an inflammatory cranial neuropathy. Giant cell arteritis temporal arteritis , can present with diplopia. Visual symptoms are present in about a third of patients - amaurosis fugax and diplopia - and in about half of cases these effects are permanent.
Sarcoidosis can present with an isolated cranial nerve lesion. Diplopia may be a complication after refractive surgery. Chronic progressive external ophthalmoplegia CPEO is a rare disorder of slowly progressive paralysis of the extraocular muscles[ 5 ]. It is usually bilateral and symmetrical with progressive ptosis followed by external ocular paresis months to years later. Ciliary and iris muscles are spared. Kearns-Sayre syndrome is a very rare mitochondrial myopathy related to CPEO but starting before the age of 20 and with pigmentary retinopathy[ 6 ].
Five red flags Pupil involvement with third nerve palsy: large poorly reactive pupil with diplopia is the most common presentation of an aneurysm of the posterior communicating artery. Diplopia affecting two or more of lip, pupil and eye movement.
Multiple cranial nerve palsies: this suggests intracranial or meningeal tumour , polyneuropathy or cavernous sinus lesion. Diplopia with weakness or fatigue: suggests myasthenia gravis. Diplopia with new-onset headache and scalp tenderness: suggests giant cell arteritis.
Investigations Diagnosing which muscles are affected is usually straightforward. A final diagnosis of the underlying cause is unlikely to be reached in primary care, so referral is usually required. Before referral, check for diabetes if it is not already diagnosed and check blood pressure in case of hypertension. MRI scan may show a tumour, an area of infarction or even an arterial aneurysm pressing on a nerve. It can also show demyelination.
CXR may reveal malignancy or sarcoidosis. Other specialist investigations may be offered depending on the suspected cause. Isolated cranial nerve palsies in patients with diabetes and hypertension do not usually need investigation unless they progress or fail to resolve over time.
Multiple nerve palsies are usually imaged, as are isolated nerve palsies in patients aged under 50 years without a long history of vasculopathy. Management Clinical management depends upon the cause. In childhood strabismus, surgery may be required although this is not always the case.
Treatment with botulinum toxin which causes flaccid paralysis is sometimes used. However, there is little clear evidence of its efficacy compared to surgical treatment, and complication rates including ptosis and vertical deviation can be high[ 7 , 8 ].
Patients with unexplained binocular diplopia and those who progress or fail to recover within a few months should be investigated further to establish the aetiology. Driving People with diplopia must not drive. They may resume driving on confirmation to the licensing authority that the diplopia is controlled by glasses or by a patch which the licence holder undertakes to wear whilst driving. Prognosis Prognosis is dependent on underlying cause. Patients with clinically isolated single nerve palsies associated with diabetes or hypertension are likely to recover within a few months, although a minority do not.
A VI nerve palsy of vascular cause typically resolves within weeks. If resolution does not occur within months, the condition progresses or, if additional neurological signs or symptoms develop, imaging studies are required.
Diplopia and III, IV and VI Cranial Nerve Lesions
Evaluation and Management