.png)
Have you ever thought about how we see colors? Why are some people able to see certain colors while others are unable to do so? Colors are all around us, imparting a complexion and pigment to everything we see, whether it's the red of an apple, the green of grass, or the light blue of the sea. Are the things we see, however, that color in reality?
Structure of The Eyes
Color perception is controlled by specific structures within the eye. All of these structures contribute to today's vibrant and colorful world. Before we get into how the various parts of the eye interact with one another, let's look at them individually.
Cornea
The cornea is the clear protective outer layer of tissue that covers the iris and pupil. When looking at the diagram of the eye the cornea looks curved but in actuality, it is flat with minimal variation in thickness. The reason the cornea bulges in the center is because of a small pocket of fluid called the anterior chamber.
As mentioned before the cornea is transparent without any blood vessels obstructing it, but nerve fibers are present so that the brain knows when the cornea is injured. Its clear state with the aqueous anterior chamber helps it refract the light at the proper angle.
Pupil
The pupil is the entrance to the eye's inner chamber. Iris muscles control the pupil, which constricts or expands to modulate the amount of light received by the eye. Pupils are dark black in color because they absorb light rather than reflecting it back.
Iris
The colored part of the eye is called the iris. It is the part that people look at to distinguish whether your eyes are blue, hazel, green, or brown, among other shades. The iris in actuality lacks these pigments. Instead, the color of an eye is determined by the amount of melanin present. Brown eyes, the most common eye color, contain more melanin and thus reflect less light. Blue and green eyes have low melanin levels and reflect a lot of light.
Lens
The lens of the eye is located right behind the pupil and is also transparent in color like the cornea. The lens along with the cornea serves the purpose of refracting light so that it is focused on the retina. It does this by changing the position which either converges or diverges light allowing objects of varying distances to be focused on.
The lens is flat on its anterior side compared to its posterior side so that a sharp image can be formed using this technique of focusing on objects at varying distances. The adjustments made by the lens are called accommodation and it is similar to the way a camera focuses to capture objects in the picture.
Retina
A thin layer of tissue that covers the back of your eye. This tissue is called the retina and it is located in proximity to the optic nerves. The retina uses the light that the lens has focused into the eye and converts it into neural signals that travel through the optic nerves on its way to the brain which is why the retina is in proximity to the optic nerves.
Optic Nerves
The optic nerve is located in the rear of the eye and is responsible for transmitting visual information from the retina to the brain's vision centers through electric impulses. Though the eyes are in front of the head the vision centers in the brain are all the way in the back. So the occipital nerves are quite long since it must travel to the back of the brain. It is made of ganglionic fibers and about 1 million nerve fibers.
In the process of traveling all the way to the occipital lobe in the back of the brain the optic nerves "cross-over" making it so that the left side of the occipital lobe controls the right side whereas the right side of the occipital lobe controls the left side.
Photoreceptors
There are two types of photoreceptors present in the eye: rods and cones.
Color in Vision
When light strikes an item, such as an apple, certain wavelengths of light reflect off of it, while other wavelengths are absorbed. The red wavelength, for example, is reflected in an apple, whereas all other wavelengths are absorbed. When a person looks at the apple, the light wave that reflects off of it meets the eye.
The cornea's appropriate light refraction allows the pupils to absorb light. The absorbed light is transmitted to the lens, which refracts it to the retina by modifying its form slightly. Photoreceptors in the eye detect the form and color of the fruit once light reaches the retina. Because rods can only perceive in black and white, the cones are the photoreceptors that take up the coloring of the apple. The light is subsequently collected by the photoreceptors, who transform it into electrical signals that are transmitted through the optic nerves. The signals are then sent all the way to the brain, which is able to analyze the item and recognize the textures and features of the apple.
Color Blindness
Color blindness is a condition that you inherit from your parents. It is caused by a mutation on the X chromosome, which is denoted by Xᶜ. The XX chromosomes are found in females, while the XY chromosomes are found in males. If the X chromosome in a female is mutated, the second X chromosome takes over and the mutation is not visible, but the female remains a carrier. Carriers are those who can pass on a mutation to their offspring but do not carry it themselves. Only if both X chromosomes are mutated, such as XᶜXᶜ, may a girl inherit the color blindness mutation. A male, on the other hand, simply needs a mutant X chromosome to acquire the XᶜY characteristic. Furthermore, because there is only one X involved in the sex chromosomes, there are no carriers in males because the X chromosome codes differently than the Y chromosome. As a result, males are more likely to inherit the colorblindness trait.
The photoreceptor structure inside the retina undergoes phenotypic modifications as a result of this mutation. Cones are the photoreceptors that allow an individual to see color, hence they are the photoreceptors that are affected. In general, there are three types of cones that sense distinct colors: red, green, and blue. These three types of cones work together to perceive colors across the spectrum, including purple, beige, gold, and many other hues. When this mutation is passed down through the generations, one or more of these types of cones become faulty, but in a person who is not color blind, all of the cones function normally. Scientists are currently investigating how the cones are defective.
Sources
Comments