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Pupillary Abnormalities -  

Fixed Pupil
Lecture 9 of 13  NEXT»

Amaurotic Pupil

The diagnosis of an amaurotic pupil is often made incorrectly because all four of the criteria for the condition are not evaluated, The observer frequently relies only on the fact that the pupil does not react to light, The criteria are (a) the blind eye has no direct reaction to light, but (b) it does react consensually, (c) the normal eye has a good direct reaction to light, but (d) it does not react consensually from a light shone in the amaurotic eye. If one were to use the lack of direct reaction to light as the only criterion, Argyll Robertson and tonic pupils would be considered blind—and obviously they are not. If the affected eye lacks both direct reaction and consensual reaction, both limbs of the pupillary arc are involved. This involvement suggests an orbital apex syndrome, since the third cranial nerve, as well as the optic nerve, are affected.

A more difficult situation arises when the patient complains of blurred vision and has a large nonreactive pupil. The initial impression may suggest optic nerve involvement also. However, the distance vision may be blurred because of an uncorrected refractive error, and the near vision may be blurred because of the loss of accommodation that becomes manifest with cycloplegia. In addition, a good consensual reaction exists in the normal eye.

Drug-Induced Cycloplegia

The possibility that the patient has either accidentally or intentionally put a cycloplegic drug in the eye should be considered. Accidental dilatation and cycloplegia can come about through the use of unlabeled eye drops that were prescribed for other eye diseases. Rubbing the sap of certain plants and flowers can also result in cycloplegia. Most of the night-blooming flowers contain Scopolamine. The physician who is confronted either with no background or with a negative neurologic examination should put one drop of a 0.5% pilocarpine solution in the affected eye. If no reaction occurs in either eye, then the test is inconclusive concerning pharmacologic blockade. In these Cases and particularly in brown eyes, 1% pilocarpine may be needed. If the patient's lityclriasis is drug induced, the motor endplates will not react to such a dilute pilocarpine solution. If the condition represents a partial third cranial nerve paralysis, however, the motor endplates are intact and will respond with the appropriate miosis.

In addition to the weak pilocarpine test for proving blockade, there may be systemic symptoms and signs that suggest a diagnosis. These include hyperpyrexia, urinary retention, dry flush skin and dry mucous membranes, psychiatric agitation, confusion and disorientation, ataxia incoordination, and visual and auditory hallucinations.



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