The part of the eye that controls the amount of light that enters is known as the pupil.

Concept: The pupil is a hole in our eye that allows light to enter.
It regulates the quantity of light that enters the eye.
The iris is a muscle in our eyes that regulates the size of our pupils. It dilates and contracts, causing the pupil size to change.
As a result, we may conclude that Iris regulates the size of the pupil.
The retina is where an image is created.
Ciliary muscles are made up of smooth muscle fibres. When the ciliary muscles relax, the lens flattens, and when they contract, the lens thickens. The focal length of the eyes changes as the curvature of the eye lens changes.
The pupil is the central aperture of the iris (the structure that gives our eyes their colour).
The pupil's job is to allow light into the eye so that it may be focused on the retina to begin the process of seeing. The pupil is typically precisely round, equal in size, and black in colour.
As a result, the iris regulates the amount of light that enters the human eye.