when to dilate eyes?
<answer> In the dark and also as a result of an illness, or another condition or emotion. <context> Eyes dilate for many reasons. They mainly dilate to control the amount of light that enters the eye. Pupils become smaller when the light is bright, and larger in the dark. Eye doctors dilate eyes to check for signs of disease. Eyes can also dilate as a result of an illness, or another condition or emotion. The circular and radial muscle of the iris control eye dilation. The radial muscle responds to dim light and will cause your pupil to become larger. The circular muscle reacts to bright light and causes the pupil to grow smaller.