Double Vision  

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Definition - The patient sees two images of the object being looked at. One is clear and the other is displaced and blurred.  A single clear image is seen when either eye is closed or occluded provided no other ocular pathology exists.  (When the eyes are misaligned, the object of regard is seen clearly by the fovea of the fixing eye and is seen blurred and displaced by the extrafoveal retina of the deviating eye. When two different objects are seen equally clearly and superimposed, visual confusion is present.  This condition is rare. )

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History Taking - Many of the questions that you ask may seem beyond the observation ability of the patient.  But if asked in an appropriate way or in several different ways the patient's recollection may surprise you.  The answers may not all be accurate, but put together with your exam the responses from the patient should provide the basis for a reasonable differential diagnosis.


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Unequal input can cause blurred vision which could be confused with diplopia

Question - Is the patient's use of the term double vision correct or do we look for another diagnosis?  It is important to be sure the patient's complaint of double vision meets the above criterion.  Many, if not most, people use the term "diplopia" or "double vision" when they really mean blurred vision which can be due to cataract, macular degeneration, corneal disease like kerataconus, optic nerve disease and many other causes.  They may even say the double vision goes away when they close one eye.   This usually means that they close the bad eye but never test it the other way around.  The patient is not purposely misinforming you or is not necessarily confused, but you perhaps did not ask the proper follow up question.  Very few patients will close one eye and then the other as a diagnostic test, because they are satisfied that the problem can be solved by simply closing one eye.



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VI N Palsy OS  

Question - Is the diplopia in one field of gaze?  If you observe that the ductions are full this is an important question.  If the patient has a complete left 6th nerve palsy, for example, then the question is unnecessary.  The question of what direction of gaze makes the double vision worse, frequently can't be answered accurately.  The patient may respond that he sees it some times but not at other times.  This can be interpreted as diplopia in one field of gaze or a transient presentation of the symptom.  If it is in one field of gaze perhaps the patient  notices it only when doing a particular task.  If he notices it upon reading or walking down stairs then a superior oblique palsy should be considered. If the patient notices it late in the day when  tired, myasthenia may be a consideration and appropriate follow up questions should be asked.  This is particularly significant in young women since 75% of all myasthenia occurrs in women under 35 years of age.  If the symptom is intermittent but not related to a time of the day or a special activity in someone over fifty, then a transient ischemic attack (TIA) needs to be considered.  Diplopia as a symptom of TIA results from posterior vascular disease such as Vertebral- Basilar disease and is not seen with disease of the carotid system.  When these symptoms are present, the examiner should ask about other signs and symptoms of Vertebral-Basilar disease, such as paresthesias, difficulty with speech, perioral paresthesias and weakness in an arm or leg.  The patient may not volunteer these symptoms since they do not occur at the same time as the diplopia. 

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Question - Is this complaint of double vision associated with any other systemic complaint that came on around the onset of his diplopia?  The patient may not relate to other symptoms but you can.  If he has headache, jaw claudication, increase in arthralgias and myalgias this would suggest cranial arteritis.  If the patient is younger and gives a history of paresthesias, optic neuritis and bladder problems then a diagnosis of demyelinating disease should be considered.

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Question - Is there a recent history of significant head trauma?  Perhaps the patient fell and struck his head severely enough to visit an emergency room but was not admitted. If the diplopia did not come on immediately with the trauma and the diplopia is horizontal then this may be a 6th nerve palsy secondary to a slowly accumulating subdural hematoma.  A fourth nerve palsy is not infrequent after a rear end collision with sudden flexion and hyperextension of the head with very little contusion of the head.  Third nerve palsy usually occurs only after severe head trauma.

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Question - Is there a past history of a tumor removed from some distant part of the body several years ago?  Patients often feel that this event is not important since the problem was cured years ago and is not now relevant.  This could represent a late metastasis.

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Horizontal and Vertical Diplopia 

Question - Is the diplopia horizontal or vertical?  If vertical, patients will frequently show it with their two hands as obliquely separated.  Spontaneous torsional diplopia after head trauma is bilateral superior oblique palsy until ruled out.  This information may be useful when doing the diplopia measurements.  If the history of onset is acute then one expects diplopia which is different in various fields of gaze (due to a noncomitant defect).  If the measurements for the horizontal portion are the same in different fields of gaze (comitant) with an acute history then those two findings do not fit.  What is frequently overlooked in this situation is a small vertical tropia in addition to a moderate horizontal deviation that has been present for a long time and is now obvious because the vertical portion disrupts fusion.  A small vertical deviation of 2 diopters may be missed in the alternate cover test when the horizontal deviation is 15 diopters.

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Primary down or

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Up gaze vertical diplopia 




Question - Is the diplopia always the same? If the images reverse position, particularly in vertical excursions, then we need to consider mechanical restriction like thyroid myopathy, blowout fracture with entrapment of a muscle, Brown syndrome, etc.  The forced duction test and the generated muscle force test are now a consideration as part of the examination. If the images vary in separation but do not reverse position, then consider a fatigue factor such as myasthenia gravis.

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Question - Is there a family history?  If there is, the patient usually volunteers it as something to be expected in his family.  However, if no information is volunteered it is always worth asking about a family history if no other causation is apparent.  A family history is frequently positive in conditions such as progressive external ophthalmoplegia or congenital fibrosis syndrome.  The condition being evaluated in the patient may be present widely scattered throughout the family and not seem important to the patient.  The family may have blamed other causes for the problem,  missing the genetic significance.

Thomas J. Walsh, M.D.