Medical examination of the pupil of the eye, or the method of testing light reflection in the eye.
From Greek koron (pupil) + -scopy (skopein, 'to examine/see'). A specialized ophthalmological term from the 19th century.
Coroscopy is what happens when an eye doctor shines a light into your pupil to watch how it responds—that reflex test is literally a medical examination of your 'crown' (the pupil)!
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