What effect does the iris have on vision?

The iris plays a critical role in vision by regulating the amount of light that enters the eye. This is achieved through its ability to constrict or dilate the pupil, the opening at the center of the iris. When there is bright light, the iris constricts to reduce the size of the pupil, allowing less light to enter, which helps prevent damage to the retina and improves visual clarity. Conversely, in low-light conditions, the iris dilates, increasing the pupil size to let in more light, enhancing the ability to see in darker situations.

This function of the iris is essential for maintaining optimal vision under varying lighting conditions, as excessive light can overwhelm the receptors in the retina, and too little light can hinder the ability to see. Therefore, the iris's regulatory mechanism directly impacts overall visual acuity and comfort.