The dark part of your eye is called the pupil. Pupils can grow or shrink according to different lighting conditions. Other factors, such as drugs, can also affect pupil size. Read on to find out which ...

Medically reviewed by Diana Apetauerova, MD Key Takeaways Anisocoria is when the pupils of your eyes are different sizes.

Miosis means excessive constriction (shrinking) of your pupil. In miosis, the diameter of the pupil is less than 2 millimeters (mm), or just over 1/16th of an inch. The pupil is the circular black ...

Dilated pupils mean that your pupils appear larger in size. The most common reason for dilated pupils is low light in a dark room since lower light causes your pupils to grow. Dilated pupils are also ...