Anisocoria with Dilated Pupil in the Affected Eye

 Complete Oculomotor Palsy

Causes:

❖ Processes in the base of the skull such as tumors, aneurysms, inflamma-tion, or bleeding.

Diagnostic considerations:

❖ Direct and consensual light reflexes without constriction in the affected eye (fixed pupil).

❖Near reflex miosis is absent.

❖ Impaired motility and double vision.

Sudden complete oculomotor palsy (loss of motor and parasympa-thetic function) is a sign of a potentially life-threatening disorder. In unconscious patients, unilateral mydriasis is often the only clinical sign of this.

Tonic Pupil

Causes: 

Postganglionic damage to the parasympathetic pathway, pre-sumably in the ciliary ganglion, that frequently occurs with diabetes mellitus, alcoholism, viral infection, and trauma.

Diagnostic considerations:

❖ Direct and consensual light reflexes show absent or delayed reaction, possibly with worm-like segmental muscular contractions.

❖ Dilation is also significantly delayed.

❖Near reflex is slow but clearly present; accommodation with delayed relaxation is present.

❖ Motility is unimpaired.

❖ Pharmacologic testing with 0.1% pilocarpine.

–  Significant miosis in the affected eye (denervation hypersensitivity).

–  No change in the pupil of the unaffected eye (too weak).

❖ Adie’s tonic pupil syndrome: The tonic pupil is accompanied by absence of the Achilles and patellar tendon reflexes.

Tonic pupil is a relatively frequent and completely harmless cause of unilateral mydriasis.

 

Iris Defects

Causes:

❖  Trauma (aniridia or sphincter tears).

❖Secondary to acute angle closure glaucoma.

❖ Synechiae (post-iritis or postoperative).

Diagnostic considerations: 

Patient history and slit-lamp examination.

Following Eyedrop Application (Unilateral Administration of a Mydriatic)

Simple anisocoria

Causes: 

Presumably due to asymmetrical supranuclear inhibition of theEdinger-Westphal nucleus.

Diagnostic considerations:

❖ Direct and consensual light reflexes and swinging flashlight test show con-stant difference in pupil size.

❖Near reflex is normal.

❖ Pharmacologic testing: Cocaine test (4% cocaine eyedrops are applied to both eyes and pupil size is measured after one hour): bilateral pupil dila-tion indicates an intact neuron chain.

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