Anisocoria refers to a common eye condition in which the two pupils differ in size. In mechanical anisocoria, this is the result of damage to the iris dilator muscle, which may be caused by trauma, angle-closure glaucoma, surgery such as cataract removal, or uveitis (inflammation of the eye). Slit lamp examination is often used as a diagnostic aid: damage to the dilator muscle is indicated by anisocoria when light intensity is lowered.
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Mechanical anisocoria Wikipedia(Text) CC BY-SA