Eye disease

Ocular media disease is an uncommon cause of diplopia and results in monocular diplopia. Examples include high astigmatism, iridectomy, decentered intraocular lens, incorrect spectacles, corneal disease or cataract. The three clues that monocular diplopia is present are:

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  the two images are not equal; one is a clear image and the other is a ghost

  
  
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  the two images are almost always touching each other

  
  
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  double vision persists despite covering one eye

Orbit or extraocular muscle disease

Thyroid orbitopathy causing restriction of one or more muscles is a common cause of diplopia and is usually easily diagnosed from the attendant orbital signs. Other causes of muscle disease, such as mitochondrial myopathy, can occur in the absence of any visible indicators of orbital disease.

Neuromuscular junction disease

Myasthenia is one of the “great mimickers” causing diplopia and can simulate a fourth, sixth or pupil-sparing third nerve palsy.

Ocular motor nerve disease

Third, fourth and sixth nerve palsies are potentially the most dangerous causes of double vision because they are often caused by an intracranial aneurysm or brain tumor compressing the nerve. Up to one-third of third nerve palsies are caused by aneurysmal compression and identification of these cases is a matter of great urgency because the aneurysm can rupture and kill the patient within hours to days of the onset of double vision; many patients with undiagnosed brain aneurysms first present to ophthalmologists with diplopia. Partial third nerve palsies can be very difficult to diagnose as they can present with many different patterns of motility disturbance (p. 204). The “rule of the pupil” is not a safe guide to whether or not an aneurysm is present (p. 207). However, the majority of third, fourth and sixth nerve palsies are caused by ischemia from atherosclerosis, diabetes or GCA (or are congenital, in the case of fourth nerve palsy).

Brain disease

A stroke, tumor or degenerative disease within the brain can present with double vision by causing an ocular motor nerve palsy, an internuclear ophthalmoplegia (INO), a skew deviation or a supranuclear palsy. The clue that a supranuclear palsy is present is that different types of eye movement (pursuit, saccadic, vestibulo-ocular, convergence) are affected to different extents.

History

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  the double vision

  
  
  
  
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    does it disappear if either eye is covered? (if it does, it is binocular diplopia; if diplopia persists despite covering one eye, it is monocular diplopia)

    
    
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    are both images the same or is one image a “ghost” (if one is a ghost, it probably is monocular diplopia)

    
    
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    are the images side by side, one on top of another or obliquely displaced?

    
    
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    does it change with distance versus near viewing?

    
    
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    does it change with direction of gaze?

    
    
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    when did it start? How quickly did it start? (very sudden onset: possible ischemic palsy or pituitary apoplexy)

    
    
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    development over time?

    
    
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    is it getting better or worse or staying the same?

    
    
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    does the severity or direction of the double vision change at different times of the day or vary from day to day? (possible myasthenia)

  
  
  
  
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  any other ophthalmic symptoms?

  
  
  
  
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    pain in or behind the eye? (ischemia, tumor, aneurysm)

    
    
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    blurred vision or field loss?

  
  
  
  
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  any neurologic symptoms: headache? Numbness, weakness, problems walking or talking?

  
  
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  previous medical and surgical history: cancer? Atherosclerotic risk factors?

  
  
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  social history: smoker?

  
  
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  if patient over 50: symptoms of GCA?

  
  
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  system review questions: any clues to the cause anywhere in the body?

Examination

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  visual acuity

  
  
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  color vision testing

  
  
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  visual field testing to confrontation

  
  
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  eye movement testing:

  
  
  
  
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    are the eyes aligned in primary position? Cover test or red-glass test, with and without glasses, distance and near

    
    
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    smooth pursuit testing of range of eye movement: both eyes open, then one eye at a time

    
    
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    are the eyes aligned differently in right gaze, left gaze, upgaze and downgaze?

    
    
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    saccades: horizontal, then vertical

    
    
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    convergence

    
    
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    vestibulo-ocular reflex (VOR) (“doll’s-head”) if a bilateral motility disturbance is found

  
  
  
  
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  pupils

  
  
  
  
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    relative afferent pupillary defect (RAPD)? (possible orbital apex syndrome from tumor)

    
    
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    anisocoria? (possible partial third nerve palsy or Horner syndrome from tumor, aneurysm or dissection)

    
    
  • –
    

    aberrant regeneration? (miosis on eye adduction or depression: possible tumor or aneurysm)

  
  
  
  
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  eyelids

  
  
  
  
  • –
    

    ptosis? (possible myasthenia; possible partial third nerve palsy or Horner syndrome from tumor or aneurysm)

    
    
  • –
    

    aberrant regeneration? (lid retraction on eye depression or adduction: possible tumor or aneurysm)

  
  
  
  
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  orbits: proptosis or enophthalmos, injection, chemosis?

  
  
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  decreased corneal or facial sensation to light touch? (possible tumor)

  
  
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  orbicularis or facial weakness? (possible myasthenia or myopathy)

  
  
• □
  

  if patient over 50: palpate temporal arteries

  
  
• □
  

  measure blood pressure in all cases

  
  
• □
  

  full neurologic examination: in all cases of unexplained diplopia

Causes

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  ocular (common)

  
  
  
  
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    cataract (most common)

    
    
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    corneal disease ( Fig. 5.1 )

    
    

    
    

    
    

    

    
    

    
    

    

    
    

    
    

    This 32-year-old man was referred for complaints of double vision; however, his eyes were straight. A , The double vision persisted when he covered his right eye; the double images were actually a main image and a ghost image that was touching the main image, and slit-lamp examination revealed a unilateral corneal epithelial dystrophy (map-dot-fingerprint dystrophy). B , The double vision improved with treatment of the corneal dystrophy.

    
    
    
    
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    high astigmatism

    
    
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    iridotomy or iridodialysis

    
    
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    decentered intraocular lens

    
    
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    ill-fitting or decentered spectacles

    
    
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    macular edema

  
  
  
  
• •
  

  brain (“cortical” diplopia), very rare: visual association cortex lesions

  
  
• •
  

  non-organic (“functional”) – rare

Symptoms

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  ocular causes

  
  
  
  
  • –
    

    usually only one eye is affected; the diplopia disappears when this eye is covered but persists when the other eye is covered

    
    
  • –
    

    the second image is often seen as a faint and blurred “ghost” of the real image

    
    
  • –
    

    images are touching each other

    
    
  • –
    

    symptoms of the cause, e.g. glare from cataract

  
  
  
  
• •
  

  brain lesion: each eye sees an identical double image; diplopia persists on covering either eye

Signs

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  ocular causes

  
  
  
  
  • –
    

    if a refractive or ocular media cause is present, the diplopia usually disappears when the patient views through a pinhole

    
    
  • –
    

    signs of the cause on slit-lamp examination

  
  
  
  
• •
  

  brain lesion: the diplopia does not disappear with pinhole

Investigations and treatment

• •
  

  ocular causes: no investigation needed, treat the cause if possible (e.g. cataract extraction, contact lens, new glasses)

  
  
• •
  

  in the very rare instance of suspected “cortical” diplopia, MRI brain with contrast

Causes

• •
  

  muscle disease

  
  
  
  
  • –
    

    thyroid orbitopathy (most commonly affecting the medial or inferior recti, causing a restrictive esotropia and/or hypotropia)

    
    
  • –
    

    orbital myositis can cause any pattern of strabismus (it can also cause a paretic myopathy due to weakness of the involved muscle/s or a combined pattern)

    
    
  • –
    

    myotoxicity after retrobulbar or peribulbar anesthetic injection

  
  
  
  
• •
  

  other orbital inflammation, e.g. orbital cellulitis, autoimmune inflammation

  
  
• •
  

  orbital trauma: muscle entrapment in orbital fractures, orbital hemorrhage

  
  
• •
  

  orbital tumors

Symptoms

• •
  

  diplopia worse in a particular direction of gaze (e.g. to the right with right medial rectus restriction)

  
  
• •
  

  myositis is often painful (with pain increased on eye movement)

Signs

• •
  

  almost always “orbital” signs are present: one or more of:

  
  
  
  
  • –
    

    eyelid retraction (very suggestive of thyroid orbitopathy)

    
    
  • –
    

    proptosis (due to inflammation or tumor) or enophthalmos (due to tight muscle/s, orbital fracture or sclerosing tumor)

    
    
  • –
    

    conjunctival injection or chemosis (may be over muscle insertion in thyroid orbitopathy or orbital myositis)

  
  
  
  
• •
  

  smooth pursuit

  
  
  
  
  • –
    

    limitation of movement of the eye in the direction opposite to the field of action of the involved muscle/s (e.g. limited abduction due to medial rectus restriction)

    
    
  • –
    

    globe retraction may occur at the limit of movement, due to the tight restricting muscle pulling the eyeball backwards in the orbit

  
  
  
  
• •
  

  saccades: normal (fast) up to the point of restriction, then an abrupt stop ( Fig. 5.2 ,Video 5.1 )

  
  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  A – C Restrictive left esotropia due to thyroid orbitopathy. The left eye cannot abduct fully due to a “tight” left medial rectus. However, the lateral rectus is still working normally, so abducting saccades are fast (not slow as in sixth nerve palsy). Note swelling of upper eyelids and lower lid retraction, left more than right.

  
  
  
  
• •
  

  forced duction test ( p. 350 )

  
  
  
  
  • –
    

    restriction to manual movement of the eye in the direction of limitation

    
    
  • –
    

    strong tug felt on active force generation testing

  
  

Investigations

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  CT scan of the orbits with contrast is usually satisfactory and has the advantage in post-traumatic cases of clearly showing orbital fractures (MRI is not good at imaging bone)

  
  
• •
  

  ultrasound may be helpful in distinguishing thyroid from other myopathies

Treatment

• •
  

  treat the underlying disease if possible

  
  
• •
  

  for thyroid eye disease, perform orbital decompression (if necessary) before strabismus surgery, then wait for stability

  
  
• •
  

  strabismus surgery: recess one or more muscles (never resect)

Causes

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  brain, nerve, neuromuscular junction disease: see the relevant sections in this chapter

  
  
• •
  

  trauma

  
  
• •
  

  orbital myositis (specific cause or idiopathic)

  
  
• •
  

  genetic myopathies, e.g. mitochondrial myopathy causing chronic progressive external ophthalmoplegia (CPEO) ( Fig. 5.3 ,Video 5.2 )

  
  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  A – F Chronic progressive external ophthalmoplegia due to a mitochondrial myopathy. This patient has bilateral ptosis and reduction of the movements of both eyes in all directions ( arrows indicate attempted directions of gaze). Saccades were slow in all directions. There was orbicularis weakness on attempted eye closure against resistance. The range of extraocular movements did not improve with “doll’s-head” vestibulo-ocular reflex stimulation (compared to progressive supranuclear palsy, in which doll’s-head testing does elicit greater movements than pursuit or saccades).

  
  

Symptoms

• •
  

  myositis is painful (with pain increased on attempting to look in the direction of action of the inflamed muscle)

  
  
• •
  

  others are usually painless

Signs

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  smooth pursuit: limitation of movement of the eye in the direction of action of the involved muscles (e.g. limited adduction due to a paretic medial rectus)

  
  
• •
  

  saccades are slow and hypometric in the direction of action of the involved muscle, with the eye coming to a gradual stop (Video 5.13 )

  
  
• •
  

  forced duction test ( p. 350 )

  
  
  
  
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    no restriction to manual movement of the eye in the direction of limitation

    
    
  • –
    

    weak “tug” felt on active force generation testing

  
  

Investigations

• •
  

  specific investigations as indicated for the diseases you suspect, for example:

  
  
  
  
  • –
    

    MRI brain for suspected brain disease or unexplained ocular motor nerve palsies

    
    
  • –
    

    acetylcholine receptor antibody blood test and ice or Prostigmin (neostigmine) test for myasthenia

    
    
  • –
    

    genetic tests for possible inherited myopathies

  
  

Treatment

• •
  

  treat the underlying disease if possible

  
  
• •
  

  strabismus surgery for paretic myopathy:

  
  
  
  
  • –
    

    wait for recovery (at least 6 months) and for the deviation to be stable on serial prism measurements of the strabismus

    
    
  • –
    

    partial paralysis: consider resecting the paretic muscle and recessing the antagonist muscle

    
    
  • –
    

    complete permanent paralysis, other muscles healthy: consider transposition strabismus surgery

  
  

Causes

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  infectious: herpes zoster ophthalmicus, fungal orbital or cavernous sinus infection (e.g. mucormycosis invading from an infected paranasal sinus)

  
  
• •
  

  neoplastic: lymphoma in particular can present acutely with red proptosed eye/s; metastases

  
  
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  vascular

  
  
  
  
  • –
    

    CCF (low or high flow) ( Fig. 5.4 )

    
    

    
    

    
    

    

    
    

    
    

    

    
    

    
    

    

    
    

    
    

    

    
    

    
    

    

    
    

    
    

    

    
    

    
    

    Acute right orbitopathy due to high-flow carotid-cavernous fistula. A Severe right proptosis, ptosis and lid swelling. B , C CT shows dilated right superior ophthalmic vein (arrows) . D Angiogram shows high-velocity arterial blood flowing from the carotid fistula into the cavernous sinus (long arrow) and then forwards through the superior ophthalmic vein into the orbit (short arrows) . E The fistula was closed by injection of platinum coils (arrow) through a catheter inserted into the femoral artery; the fistula is seen to have closed and the anterior flow through the superior ophthalmic vein has ceased. F The coils on a plain skull x-ray (arrow) .

    
    
    
    
  • –
    

    CST (septic or sterile)

    
    
  • –
    

    GCA

    
    
  • –
    

    orbital ischemic syndrome from internal carotid artery (ICA) stenosis or occlusion

  
  
  
  
• •
  

  autoimmune inflammatory

  
  
  
  
  • –
    

    specific orbital inflammation (e.g. Wegener granulomatosis, sarcoid)

    
    
  • –
    

    non-specific (idiopathic) orbital inflammation (“orbital pseudotumor”)

  
  

Symptoms

• •
  

  change in appearance (often marked): red eye/s, proptosis

  
  
• •
  

  often pain, “pressure” sensation or headache (may be severe)

  
  
• •
  

  ± symptoms of ophthalmic complications including:

  
  
  
  
  • –
    

    diplopia

    
    
  • –
    

    blurred vision due to optic neuropathy

  
  
  
  
• •
  

  ± symptoms specific to particular causes, for example:

  
  
  
  
  • –
    

    pulsatile tinnitus (“whooshing” noise heard by the patient in time with their pulse) in CCF

    
    
  • –
    

    fevers in infection

    
    
  • –
    

    fatigue and weight loss in chronic infection, vasculitis or cancer

    
    
  • –
    

    symptoms of GCA

  
  

Signs

• •
  

  unilateral or bilateral red eye ± proptosis (mild to severe)

  
  
• •
  

  ± conjunctival chemosis

  
  
• •
  

  ± acquired strabismus with limitation of motility in one or more (sometimes all) directions

  
  
• •
  

  ± signs specific to particular causes, such as:

  
  
  
  
  • –
    

    increased temperature and pulse rate in orbital cellulitis or septic CST

    
    
  • –
    

    bruit audible with stethoscope, palpable pulsatile proptosis, increased ocular pulse pressure on tonometry and/or dilated tortuous conjunctival vessels in high-flow CCF

    
    
  • –
    

    necrotic black periorbital skin or nasal tissue in fungal orbital apex or cavernous sinus infection

    
    
  • –
    

    retinal venous dilation or retinal hemorrhage (or frank central retinal vein occlusion) may occur in all but is more likely in CCF and CST

    
    
  • –
    

    confusion, headache, loss of consciousness in high-flow CCF, CST or brain infection secondary to orbital cellulitis

    
    
  • –
    

    decreased vision ± sluggish pupils or RAPD due to:

    
    
    
    
    • –
      

      central retinal vein or artery occlusion (caused by increased intraocular pressure or venous drainage obstruction)

      
      
    • –
      

      ischemic, compressive, inflammatory or infiltrative optic neuropathy

      
      
    • –
      

      keratopathy, corneal ulcer or perforation (due to exposure from proptosis, neurotrophic ulcer secondary to loss of corneal sensation or from anterior segment ischemia)

      
      
    • –
      

      intraocular inflammation (anterior, posterior or panuveitis): infectious, inflammatory, neoplastic or ischemic

    
    

  
  

Investigations

• •
  

  urgent (same-day) orbit and brain imaging

  
  
  
  
  • –
    

    CT is often more readily available than MRI and is a reasonable first option as long as dedicated high-resolution orbital and cavernous sinus views are obtained, with contrast (“CT brain” alone is of little value). Ask for: magnified axial and coronal fine-cut CT orbits, plus CT brain with cavernous sinus views, with contrast

    
    
  • –
    

    this will identify most orbital tumors and collections that can present with acute orbitopathy and shows bone erosion (from cancer) better than MRI

    
    
  • –
    

    MRI provides better resolution of the orbital apex and cavernous sinus

    
    
  • –
    

    ultrasound may be helpful in distinguishing some types of orbital lesions

    
    
  • –
    

    however, many diffuse orbital processes (infection of any cause, lymphoma, autoimmune inflammation) all look the same on imaging (diffuse increase in signal in the orbital soft tissue) so other investigations are needed to determine the underlying cause

    
    
  • –
    

    whichever scan you get, look specifically to see whether there is a:

    
    
    
    
    • –
      

      solid tumor mass

      
      
    • –
      

      drainable orbital pus collection

      
      
    • –
      

      opacification of one or more of the ethmoid, maxillary or sphenoid sinuses (possible primary infection or cancer which has then spread into the orbit)

      
      
    • –
      

      dilated superior ophthalmic vein: this is the most reliable CT or MRI sign of a CCF–MRA and MR venography (MRV) may be of value in the diagnosis of this condition

      
      
    • –
      

      enlargement of one or more of the extraocular muscles

      
      
    • –
      

      enlargement or enhancement of the optic nerve

    
    

  
  
  
  
• •
  

  other investigations required may include:

  
  
  
  
  • –
    

    blood tests for thyroid function, infectious and autoimmune causes

    
    
  • –
    

    chest x-ray looking for primary or secondary cancer, tuberculosis or sarcoidosis

    
    
  • –
    

    transnasal endoscopic aspiration and biopsy of a potentially infected or cancerous ethmoid or sphenoid sinus (specimen to microbiology, histology, cytology)

    
    
  • –
    

    direct orbital biopsy

    
    
  • –
    

    lumbar puncture

    
    
  • –
    

    chest and abdomen CT or MRI and/or bone scan, looking for primary or secondary neoplastic lesions

    
    
  • –
    

    catheter angiography for diagnosis (± treatment) of CCF

  
  

Treatment

• •
  

  treat the underlying cause, for example:

  
  
  
  
  • –
    

    intravenous antibiotic treatment ± surgical drainage or debridement of infection

    
    
  • –
    

    endovascular occlusion of a CCF

    
    
  • –
    

    anticoagulation for CST

    
    
  • –
    

    chemotherapy and radiotherapy for lymphoma

    
    
  • –
    

    immunosuppression for specific or non-specific autoimmune inflammation

  
  
  
  
• •
  

  protect the eye

  
  
  
  
  • –
    

    lower intraocular pressure if necessary (medically or with orbital decompression)

    
    
  • –
    

    protect the cornea if exposed (especially if the cornea is also anesthetic)

  
  

Mechanism

• •
  

  autoantibodies directed against the acetylcholine receptors are produced, circulate in the blood and destroy or block many of the receptors

  
  
• •
  

  the decreased number of functioning acetylcholine receptors results in the fatigability that is so often seen clinically: on repeated or sustained contraction, fewer receptors are available for activation and the strength of the muscle fades

Causes

• •
  

  idiopathic myasthenia (in most cases)

  
  
• •
  

  medications: “drug-induced” myasthenia (penicillamine, aminoglycosides, beta blockers, chlorpromazine, etc.)

Symptoms

• •
  

  these usually have a gradual onset and are usually initially mild or intermittent. However, in some cases there is the acute onset of severe ophthalmic and/or systemic symptoms

Signs

Abnormal ocular motility ( Figs. 5.5 and 5.6 ,Videos 5.3 and5.4 )

• •
  

  myasthenia can:

  
  
  
  
  • –
    

    mimic any other cause of strabismus, including unilateral or bilateral pupil-sparing partial or complete third nerve palsy, fourth nerve palsy or sixth nerve palsy or INO

    
    
  • –
    

    (usually) cause an incomitant strabismus, with any pattern of limitation of movement of one or both eyes (including underaction of a single muscle on one side)

    
    
  • –
    

    (rarely) present as a gradual or acute-onset comitant strabismus, with no obvious limitation of movement in any direction

    
    
  • –
    

    cause intermittent diplopia, with an entirely normal motility examination when you see the patient

    
    
  • –
    

    present as a horizontal or vertical gaze palsy without diplopia

  
  
  
  
• •
  

  the principal examination clue that myasthenia is present is demonstrating “clinical fatigability”

  
  
  
  
  • –
    

    make the patient hold their gaze in the direction of the worst limitation of motility

    
    
  • –
    

    as the affected muscle fatigues, the eye may slowly drift back towards primary position

    
    
  • –
    

    this is not completely specific for myasthenia (partial nerve palsies can also show fatigability) and neither does the absence of demonstrable fatigability rule out myasthenia

    
    
  • –
    

    an alternative is to make repetitive saccades in the direction of action of the affected muscle/s; it should be noted that, as opposed to the slow saccades of myopathy or neuropathy, saccades may be of normal velocity or slow in myasthenia but (especially with fatigue) become hypometric: smaller than they should be, with the eye “undershooting” the target

  
  
  
  
• •
  

  “gaze-paretic nystagmus”

  
  
  
  
  • –
    

    this can be seen in extraocular muscle weakness of any cause (nerve palsy, myasthenia or paretic myopathy)

    
    
  • –
    

    it occurs due to increased innervation to the agonist muscle of the other eye, if a patient with a paretic muscle is asked to look in the direction of action of the weak muscle

    
    
  • –
    

    the importance of this is that myasthenia can very closely mimic INO if it affects mainly the medial rectus muscle, with gaze-paretic nystagmus being seen in the other (abducting) eye on attempted adduction of the affected eye

    
    
  • –
    

    for example, if myasthenia is affecting only the left medial rectus, on attempted right gaze the patient may show decreased adduction of the left eye and jerk nystagmus of the abducting right eye

  
  

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