- Anatomy and Basic Properties
- Pupil is central opening of iris, appearing black due to light absorption
- Circular in humans, but varies between species: vertical in cats, horizontal in goats
- Size controlled by iris muscles: sphincter constricts, dilator dilates
- Function and Regulation
- Pupillary light reflex controls amount of light entering eye
- Dark-adapted pupil diameter ranges from 2-4mm, bright-adapted from 3-8mm
- Pupil constricts in bright light to prevent light aberrations
- Clinical Significance
- Drugs like pilocarpine constrict pupils, atropine dilates them
- Bene dilitatism causes chronically widened pupils due to optic nerve damage
- Pupil size can indicate emotional arousal and cognitive activity
- Evolutionary and Cultural Aspects
- Slit pupils evolved for better light exclusion in nocturnal animals
- Pupil shape correlates with animal activity patterns and foraging behavior
- Term "pupil" means "little person" in many unrelated languages