Light enters the eye through the transparent cornea, passes through the aqueous humor, the lens, and the vitreous humor, where it finally forms an image on the retina (see Figure 1). When these photoreceptors are stimulated by light, they produce electrical signals that are transmitted to the brain via the optic nerve.

The cornea and lens of an eye act together to form a real image on the light-sensing retina, which has its densest concentration of receptors in the fovea and a blind spot over the optic nerve. The power of the lens of an eye is adjustable to provide an image on the retina for varying object distances.

In astronomy, the naked eye may be used to observe celestial events and objects visible without equipment, such as conjunctions, passing comets, meteor showers, and the brightest asteroids, including 4 Vesta.

Together with the pupil, the iris is responsible for regulating the amount of light that gets into the eye. Too much or too little light can hamper vision. The muscular iris moves to shrink the pupil if there is too much light and widen it if there is not enough.

The function of the iris in the eye is to control the amount of light that reaches the retina. It does this by changing the size of the pupil, the transparent window that allows light into the eye’s interior.

In humans and most mammals and birds, the iris (plural: irides or irises) is a thin, annular structure in the eye, responsible for controlling the diameter and size of the pupil, thus the amount of light reaching the retina. Eye color is defined by that of the iris.

Iris: behind the cornea is a coloured diaphragm called the iris. it is an extension of the choroid. the iris gives the eye its characteristics colours. for example, a blue- eyed person has blue iris and a black-eyed person has black iris.

What are the parts of the eye that make up vision?

• Cornea: This is the front layer of your eye.
• Pupil: The pupil is the black dot in the center of your eye that acts as a gateway for light.
• Iris: This part is typically referred to as your eye color.
• Lens: The lens is behind the iris and pupil.

The outer covering of the eyeball consists of a relatively tough, white layer called the sclera (or white of the eye). Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a thin, transparent membrane (conjunctiva), which runs to the edge of the cornea.

While babies’ eyes are developed at birth, it takes up to 2 years for eyesight to fully develop. Eyes grow rapidly after birth and again during puberty until age 20 or 21, when they stop growing in size.

Nose

While the rest of our body shrinks as we get older, our noses, earlobes and ear muscles keep getting bigger. That’s because they’re made mostly of cartilage cells, which divide more as we age.