How are ocular motor functions evaluated in patients with suspected diplopia?

Updated: May 21, 2019
  • Author: Jitander Dudee, MD, MA(Cantab), FACS, FRCOphth; Chief Editor: Andrew G Lee, MD  more...
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Answer

The motor aspect of the physiologic evaluation includes the following:

  • Determine the existence of a normal range of ocular movements. First observe each eye separately (ocular ductions), and then observe both eyes together (ocular versions). Careful consideration of the extraocular muscle anatomy clarifies the effect of each muscle and why one direction of gaze isolates each muscle's effects.
  • Determine that each eye is able to fully adduct (turn inward) and abduct (turn outward) and to fully elevate and depress in abduction and adduction (as if the eye is tracing a capital letter "H").
  • This helps to determine which eye muscle is responsible for diplopia; normal contraction of the medial rectus muscle produces adduction, while abduction is caused by the lateral rectus muscle. Because the vertical eye muscles diverge from their origination at the apex of the orbit to the insertion on the globe, the superior and inferior recti muscles can be evaluated best with the eye abducted.
  • With the eye abducted, the eye will move down by the inferior rectus muscle, while the superior rectus muscle will move it upward in abduction. Likewise, the oblique muscles can be isolated with the eye adducted; with the eye turned in, the inferior oblique muscle elevates and the superior oblique muscle depresses the eye. A simple rule for superior oblique weakness is "the eye that is looks highest in adduction is pointing at the affected superior oblique muscle."
  • Determine if diplopia worsens when the muscles are fatigued (eg, after strenuous use, at the end of the day). Myasthenia gravis can affect any muscle or group of muscles, and a common presenting symptom is variable diplopia. If myasthenia gravis is suspected, its diagnosis can be confirmed with a rest or sleep test or an ice test or after intravenously injecting a short-acting anticholinesterase (ie, 10 mg/mL edrophonium chloride [Tensilon]). Nonpharmacologic tests for myasthenia gravis have become more popular and more widely used clinically because of their ease of use and lack of significant adverse-effect profile compared with pharmacologic testing. See Other Tests.

Determine that other ocular motor functions are normal, as follows:

  • Is the lid in a normal position? (eg, lid retraction in thyroid eye disease or aberrant regeneration of the third nerve, ptosis, Cogan lid twitch sign, enhancement and variability in myasthenia gravis)
  • Is the pupil response normal and symmetric with the other pupil? Pupil asymmetry is a sinister sign when associated with diplopia because it indicates involvement of the third cranial nerve (oculomotor nerve). An important diagnostic clue is provided by detecting pupil sparing but otherwise complete third nerve palsy (eg, ptosis; inability to elevate, depress, or abduct the eye). A pupil whose function is spared, particularly if associated with complaints of headache or pain around the orbit, suggests diabetic third nerve palsy. This can avoid expensive and unnecessary imaging studies. Complete and spontaneous recovery after approximately 6 weeks is virtually the rule. Similar temporary mononeuritis multiplex processes can affect the sixth cranial nerve (abducens) with temporary loss of abduction.

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