The curvature of the eye lens is modified by the ciliary muscles, which are responsible for changing the shape of the lens. These muscles play a crucial role in adjusting the curvature of the eye lens.

The light-sensitive cells in the retina, upon illumination, generate electrical signals. These signals are transmitted to the brain via the optic nerves. The brain interprets and processes these signals, allowing us to perceive objects as they are.

The pupil, controlled by the iris, adjusts in size to regulate the amount of light entering the eye. In bright conditions, the pupil constricts to reduce the light, while it dilates in low-light conditions to allow more light in.

The crystalline lens provides a finer adjustment of focal length to focus objects at different distances on the retina, complementing the main refraction occurring at the outer surface of the cornea.

The iris, a dark muscular diaphragm behind the cornea, controls the size of the pupil. By adjusting the size of the pupil, the iris regulates and controls the amount of light entering the eye.