Image formation by an eye is based on the passage of light in the eye. It is an instant process.
1. Firstly, the light enters the eye and passes through the transparent cornea to the pupil in the centre of the iris.
2. Then, the adjustable lens and the fixed cornea focus the light rays on the retina to form a clear image.
3. The entire image formation process depends on the nerve signals. The optical nerves present in the eye convey the image as an electrical impulse towards the brain. The optic centres of the brain process the image formation and a clear image is formed on the retina.