Question

Name the important parts of the eye and explain their functions

Answer 1

The iris is the colored part of the eye. It is important because it controls the size of the pupil. The pupil is the dark circle inside the center of the eye. The dark hole is altered in shape by the iris, affecting the amount of light that is let into the eye. The pupil is large when light is low or it is dark outside and tiny when it is very sunny or bright.

The cornea is the clear covering over the pupil and iris. This is the reason that contacts are dome shaped because they sit on the cornea. The cornea provides 66% of the optic power that the overall eye has. This means that the cornea is very important in focusing what we see by bending light.

The sclera is the white part of the eye that we see in the mirror that becomes pink or red when we are tired or have sneezed so hard that our eyes become bloodshot. This eye part is the protective, outer layer of the eye. It is made up of elastic-like fibers called elastin and collagen, a common connective tissue found in mammals.

The eyeball is held in place by the eyelid, which is the first protective layer. The eyelid has an inner layer of skin called conjunctiva. The conjunctiva covers the sclera and provides mucus and tears for eye lubrication and bacterial infection prevention. It does not cover the cornea.



The Back of the Eye

In the back of the eye, are the important items that we cannot see when we look in the mirror. This area consists of the:

Lens

Vitreous

Retina

Macula

Fovea

Optic nerve

These parts have important independent functions. The lens of the eye works in conjunction with the cornea. This part is also important for light refraction and focusing of images onto the retina. The lens can change shape to fine tune focus, change focal distance, and create a sharp image.

The vitreous is the clear, thick gel-like substance between the lens and retina. The function of the vitreous gel is to help with optical power, maintain eye structure and retinal health. It is very clear, 98% water, and doesn't change from birth, unlike many fluids in the body that are replenished throughout life.

The retina is a tissue that lines the inner surface of the eye. It senses light brought through from the cornea, pupil, and lens, and is where the image of the world appears after focusing. The macula is where very fine focus occurs. The macula has inside it the fovea, which has tightly packed cones in it that sense color. All of these parts of the retina can be thought of like the film of a movie or a camera.

Answer 2

Light is focused primarily by the cornea — the clear front surface of the eye, which acts like a camera lens.The iris of the eye functions like the diaphragm of a camera, controlling the amount of light reaching the back of the eye by automatically adjusting the size of the pupil (aperture).The eye's crystalline lens is located directly behind the pupil and further focuses light. Through a process called accommodation, this lens helps the eye automatically focus on near and approaching objects, like an autofocus camera lens.Light focused by the cornea and crystalline lens (and limited by the iris and pupil) then reaches the retina — the light-sensitive inner lining of the back of the eye. The retina acts like an electronic image sensor of a digital camera, converting optical images into electronic signals. The optic nerve then transmits these signals to the visual cortex — the part of the brain that controls our sense of sight.