Seeing things is one of the basic senses that humans and other organisms are blessed with. The eyes are the organs responsible for the purpose of seeing in the organism. The process of seeing is made possible by the presence of photoreceptors in the retina, which is the third and inner layer of the eye. hay approx. 125 million photoreceptors in a human eye, which use electromagnetic radiation in neural signals. These photoreceptors can be mainly divided into two types; Cones and rods. Both photoreceptors differ based on their structure, sensitivity, photochemical molecules, and function. Rods are the rod-shaped photoreceptors that provide vision in dim light (night), while cones are the cone-shaped photoreceptors that provide vision. vision in bright light.
|Shape||The rods are the rod-shaped photoreceptors.||The cons are the cone-shaped photoreceptors.|
|Function||The rods provide vision in dim light (night).||Cones provide vision in bright light (daylight).|
|Pigment||The rods contain the pigment rhodopsin, which is made up of vitamin A||Cones contains the pigment iodopsin.|
|Quantity||Of the total 125 million photoreceptors in the human eye, about 120 million photoreceptors are rods.||5 million are cones.|
|Location||The rods are located near the periphery of the retina.||Cones are present in the center of the retina.|
|Deficiency||The lack or deficiency of rhodopsin, which is the pigment of the rods, can cause night blindness.||Lack or deficiency of iodopsin, the pigment present in the cones can result in color blindness.|
What are rods?
The rods are the abundant photoreceptors, located on the periphery of the retina. They are rod-shaped and are responsible for providing vision at night or at twilight when lights are dim. Of the total 125 million photoreceptors in the human eye, about 120 million photoreceptors are rods. The rods contain a purplish pigment, which is known as visual purple or rhodopsin. These rhodopsins are made up of vitamin A and work effectively in low light at night or at dusk. Rods are the important component of the eye or retina that makes people see at night; its deficiency can lead the body to diseases such as night blindness. As the name of the disease says, it is difficult for the person suffering from it to see in the dark,
What are the cones?
The cones are the photoreceptors located in the center of the retina. They are the cone-shaped receptors responsible for daytime night vision. The cones function efficiently when bright light is off, although they are quite minor in number compared to the other rod photoreceptors, they provide a primary function of vision under bright light, be it daylight or artificial light. These cones not only give detailed images, but they also give color vision, or in other words, we can say that they help us to distinguish between different colors. Based on providing color vision, there are three types of cones; blue, red and green. Cones contains the violet-colored pigment, which is called visual violet or iodopsin.
rods vs. cones
- The cons are the cone-shaped photoreceptors, while the rods are rod-shaped.
- Cones provide vision in bright light (daylight), while rods provide vision in dim light (night).
- The rods contain the pigment rhodopsin, which is made up of vitamin A, while the cones contain the pigment iodopsin.
- Of the total 125 million photoreceptors in the human eye, about 120 million photoreceptors are rods and the remaining 5 million are cones.
- Rods are found near the periphery of the retina, while cones are present in the center of the retina.
- The lack or deficiency of rhodopsin, which is the pigment in the rods, can cause night blindness, while the lack or deficiency of iodopsin, the pigment in the cones, can result in color blindness.