What is diplopia? Diplopia is seeing an object as two objects. Diplopia is also known as double vision. Diplopia occurs when the extra ocular muscle fails to work together. This will cause the image to fall on the retina at the non responding areas. Impairment of the function of the cranial nerves such as third cranial nerve ( oculomotor nerve), fourth cranial nerve ( trochlear nerve ) and sixth cranial nerve ( abducens nerve) that supply the extra ocular muscle, the effect of surgery or orbital lesions may cause diplopia.
Diplopia initially affects the far or near vision intermittently. Diplopia may be binocular or monocular. Monocular diplopia may occur as a result of subluxated lens, astigmatism (uncorrected refractive error), poorly fitting contact lens, iridodialysis, retinal scaring, retinal edema and early cataract. Binocular diplopia may occur as a result of psychoneurosis, ocular displacement, ocular deviation and extraocular muscle palsies. Malingering and hysteria may also cause diplopia.
Neurological status should be inspected if the patient complain of diplopia. Assess the patient level of consciousness. Observe the motor and sensory response. Inspect the pupils and look for any equality of the pupil response to the light and sizes of the pupil. Vital signs is taken. It is important to discuss any associated neurological symptoms such as headache as it may lead to serious complications.
The patient is asked when he first noticed the double vision. Are the images vertical ( one above another) or horizontal ( one sides by sides) or combination of both ? Does the diplopia affect certain point of gaze? Does the diplopia affect the far or near vision? Has the diplopia subsides, remain the same or getting worst? Does the diplopia worsen at certain time of the day? Diplopia that occurs or worsens in the evening suggestive of myasthenia gravis. Certain cases of diplopia can be corrected by tilting the head, This is associated with fourth cranial nerve palsy and sixth cranial nerve palsy. In fourth cranial nerve palsy , tilting the head towards the opposite shoulder causing the unaffected eye to undergo compensatory tilting. In sixth cranial nerve palsy ,tilting the head towards the paralyzed muscle may cause relaxation of the lateral muscle.
Other associated symptoms should be explore such as eye pain or any medical disorders such as muscular or neurological disorders, thyroid problems, allergies, diabetes mellitus and hypertension. Any history of eye surgery, trauma or extraocular muscle disorder should be noted.
The patient is observed for any conjunctival injection, lid edema, proptosis, ptosis and ocular deviation. The patient is asked to occlude one of the eye. He has monocular diplopia if he still able to see double out of one eye. Check and test the patient’s extraocular muscle and visual acuity.
The main causes of diplopia are eye surgery, transient ischemic attack, thyrotoxicosis, stroke, orbital tumor, orbital cellulitis, orbital blow out fractures, ophthalmologic migraine, myasthenia gravis, multiple sclerosis, intracranial aneurysm, head injury, encephalitis, diabetes mellitus, cavernous sinus, thrombosis, brain tumor, botulism and alcohol intoxication.
Eye surgery may cause fibrosis which restrict the eye movement and cause diplopia.
Diplopia may occur as a result of transient ischemic attack. The transient ischemic attack may last for a few seconds or up to 24 hours. The present of transient ischemic attack is an indication of future episodes of stroke. Besides diplopia, other signs of transient ischemic attack are dizziness, numbness, hearing loss and tinnitus.
Thyrotoxicosis may cause diplopia especially when the thyroid disorder is accompanied by exophthalmos. It is initially begins with infiltrative myopathy of the inferior rectus muscle which affect the upper gaze. It is associated with other signs of the eyes such as inability to close the eyelid , lid edema, excessive tearing and impaired eye movement. Always note the other cardinal signs of thyrotoxicosis such as heat intolerance, diaphoresis, nervousness, dyspnea, enlarged thyroid gland, trauma, tachycardia , diarrhea , weight loss and palpitation.
Diplopia is also associated with stoke due to its effect on the vertebrobasilar artery. Other symptoms and signs of stroke are paralysis, unilateral motor weakness, decrease level of consciousness, amnesia, dysphagia, slurred speech, circumoral numbness, visual field defect , aphasia and dizziness.
Orbital tumor that is large in size may cause blurred vision, proptosis and diplopia. Orbital cellulitis may cause sudden onset of diplopia. Orbital cellulitis is an inflammation of the eyelids and the orbital tissue. Other findings are fever, nausea, proptosis, redness, chemosis, lid edema, purulent drainage, eye pain and eye deviation.
Trauma such as orbital blowout fracture may cause upward gaze monocular diplopia. However, diplopia may affect other direction due to marked peri orbital edema. The orbital fracture may not affect the visual acuity. However, it may cause periorbital ecchymosis. Subcutaneous crepitation of the eyelid and orbit are also common. The patient’s pupil is occasionally unresponsive and dilated as well as hyphema may occur.
Ophthalmologic migraine occur in young adults and may cause diplopia which last for days following headache. Other signs and symptoms are depression, irritability, slight confusion, extra ocular muscle palsies and severe unilateral pain.
Initially , myasthenia gravis present with ptosis and diplopia which worsen throughout the day. The condition then progress into blank facial expression, difficulty making fine hand movement, swallowing or chewing , nasal voices and life threatening weakness of the respiratory muscle.
Diplopia , blurred vision and paraesthesia are the common early signs of multiple sclerosis. Other signs and symptoms as multiple sclerosis progress are constipation, nystagmus, muscle weakness, spasticity, paralysis, intention tremor, hyperreflexia, dysphagia, ataxia, dysarthria, emotional lability , impotence, urinary frequency, incontinence and urgency.
Intracranial aneurysm is a life threatening condition which is presented with eye deviation, diplopia, ptosis and dilated pupil on the affected sides. The patient will complain of severe, recurrent, frontal headache which is unilateral. The headache may become violent after the rupture of the aneurysm. Other signs and symptoms are spinal and neck pain as well as rigidity , a decrease in the level of consciousness, nausea, dizziness, vomiting, tinnitus, paralysis and unilateral muscle weakness.
Head injury which is life threatening in nature may cause diplopia depending on the extent and the sites of injury. Other signs and symptoms are pupillary changes, eye deviation, decrease level of consciousness, headache, eye deviation, altered vital signs, paralysis ,motor weakness, vomiting and nausea.
Encephalitis is initially presented with sudden onset of a high fever, vomiting, severe headache and brief episodes of eye deviation and diplopia. later as the disease progress, the patient may shows signs of meningeal irritation, paralysis a, ataxia ,seizures and decrease level of consciousness.
Diplopia may occur as a long term effect of diabetes mellitus due to isolated third cranial nerve palsy. Diplopia will be accompanied by pain in the eye.
Cavernous sinus thrombosis may cause diplopia , proptosis, limited eye movement, lid and orbital edema, fever, papilledema, impaired visual acuity, diminished or absent pupillary response.
The early signs of brain tumor is diplopia. Other signs and symptoms are based on the location and sizes of the tumor. These include decrease level of consciousness, emotional lability, eye deviation vomiting, headache, ,generalized tonic clonic seizures, absence seizures, visual field deficits, hearing loss, nystagmus, paralysis, motor weakness and abnormal pupillary response.
The common signs of botulism are ptosis, dysphagia, dysarthria and diplopia. The initial findings are sore throat, dry mouth, diarrhea and vomiting. Then paralysis or descending weakness of the trunk and extremity which may cause dyspnea and hyporeflexia.
The symptoms and signs of alcohol intoxication are diplopia,conjunctival injection, vomiting, nausea, behavior changes, staggering gait, halitosis, slurred speech and confusion.
In children, strabismus may cause diplopia. However, the brain may compensate for double vision rapidly by suppressing one image. This will lead to the absent of diplopia in a young patient. Serious disorder such as brain tumor should be rule out if any school children reporting for episodes of diplopia.
It is important to continue assessing the vital signs of the patient as well as the neurological status in case of any acute neurological disorders. The patient is prepared for neurological test and CT scan. A save environment is essential and remove any obstacle as well as assisting the patient ambulation. The patient is advices not to operate heavy machinery or drive a car while having a double vision or diplopia.
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