Pupillák

Pupillák are the dark circular openings in the center of the iris of the eye. Their primary function is to allow light to enter the eye and reach the retina, enabling vision. The size of the pupil is controlled by two muscles in the iris: the sphincter pupillae, which constricts the pupil, and the dilator pupillae, which dilates it. This pupillary reflex is largely involuntary and responds to changes in ambient light. In bright conditions, the sphincter pupillae contracts, making the pupil smaller to reduce the amount of light entering the eye and prevent overstimulation of the retina. In dim light, the dilator pupillae contracts, causing the pupil to widen and allow more light in to improve vision in low-light environments.

Pupil size can also be influenced by other factors. Emotional states, such as fear or excitement, can lead to pupil dilation through the sympathetic nervous system. Certain medications, drugs, and medical conditions can also affect pupil size and reactivity. For example, some eye drops used for dilation during eye exams work by relaxing the sphincter pupillae muscle. In neurological examinations, the size and responsiveness of the pupils are important indicators of brain function. Abnormalities in pupil size or symmetry can suggest potential neurological issues. The phenomenon of pupils appearing to "follow" each other is known as the consensual pupillary light reflex, where light shone into one eye causes both pupils to constrict.