värikalvolihas

Värikalvolihas, also known as the iris sphincter muscle, is a part of the eye's iris. It is a circular muscle that surrounds the pupil. When this muscle contracts, it constricts the pupil, making it smaller. This action is part of the pupillary light reflex, which helps regulate the amount of light entering the eye. In bright light conditions, the värikalvolihas contracts to reduce pupil size, thereby protecting the retina from overexposure. Conversely, in dim light, it relaxes, allowing the pupil to dilate and capture more light for better vision. The nervous system controls the contraction and relaxation of the värikalvolihas through the parasympathetic nervous system. This muscle plays a crucial role in visual acuity and adapting to varying light environments. Its function is involuntary, meaning it operates automatically without conscious thought. Diseases or damage affecting the värikalvolihas can lead to vision problems, including impaired light adaptation and difficulties with pupil size regulation.