Pupil
A pupil was the dark area of an eye surrounded by the iris. The function of the pupil was to control the amount of light allowed to pass into the eye.

The dilation of one's pupils could be an indicator of dishonesty. () Talaxians and Humans both experienced pupil dilation when attracted romantically to others. () Some species, such as the Myleans, had naturally dilated pupils, which made them intolerant of bright light. ()

Alternately, the contraction of one's pupils could be an indicator of illness. In 2370, Doctor Julian Bashir noted that Elim Garak's pupils were contracted and his skin was clammy when the Cardassian was experiencing headaches. ()

In 2377, The Doctor noted that Seven of Nine's pupils dilated by nearly a millimeter and her blood flow increased to her facial capillaries when she mentioned Axum. ()

Species 8472 had distinctive cross-shaped pupils. ()

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Anatomy