Which layer of the eye is pigmented and helps regulate light entry?

The iris is the layer of the eye that is pigmented and plays a crucial role in regulating the amount of light that enters the eye. It is a circular structure located behind the cornea and in front of the lens. The amount of pigment in the iris gives eyes their color, which can range from blue to brown, affecting how much light is absorbed and reflected.

The iris contains muscles that can contract or dilate in response to the light conditions. In bright light, the muscles contract to make the pupil smaller, reducing the amount of light that enters and protecting the retina from excessive brightness. Conversely, in low light conditions, the muscles relax, causing the pupil to dilate and allowing more light to enter the eye for better visibility.

This regulation of light entry is essential for optimal vision and helps prevent damage to the delicate structures within the eye. The other layers of the eye, such as the cornea, retina, and sclera, have distinct functions, but they do not actively regulate light entry in the manner that the iris does.