Which pupil finding describes dilation due to compression of the superficial pupillary fibers by a mass?

Which pupil finding describes dilation due to compression of the superficial pupillary fibers by a mass?

• A. Hutchinson's Pupil
• B. Adie's Pupil
• C. Tonic Pupil
• D. Argyll Robertson Pupil

Answer: (A)

When a mass presses on the oculomotor nerve, the superficial parasympathetic fibers that control the iris sphincter are the first to be affected. Damaging these fibers removes the constriction signal to the pupil, so the pupil enlarges and becomes poorly reactive to light. This pattern—pupil dilation due to compression of the superficial pupillary fibers by a mass—is classically described as Hutchinson's pupil. Adie's (tonic) pupil is a dilated pupil with slow or irregular reaction to light due to postganglionic parasympathetic (ciliary ganglion) dysfunction, not mechanical compression. Argyll Robertson pupils are small, irregular, and accommodate but do not react to light, seen in neurosyphilis, not a dilated response from mass effect.

When a mass presses on the oculomotor nerve, the superficial parasympathetic fibers that control the iris sphincter are the first to be affected. Damaging these fibers removes the constriction signal to the pupil, so the pupil enlarges and becomes poorly reactive to light. This pattern—pupil dilation due to compression of the superficial pupillary fibers by a mass—is classically described as Hutchinson's pupil.

Adie's (tonic) pupil is a dilated pupil with slow or irregular reaction to light due to postganglionic parasympathetic (ciliary ganglion) dysfunction, not mechanical compression. Argyll Robertson pupils are small, irregular, and accommodate but do not react to light, seen in neurosyphilis, not a dilated response from mass effect.