The human eye retina has photoreceptor cells. These cells are responsible for absorbing light and converting light into a signal that triggers visual phototransduction due to membrane change.
According to science, these photoreceptor cells help in vision in the presence of light. The main types of photoreceptor cells are rod and cone cells.
So, what is the main difference between rods and cones? The former does not give color vision due to a lack of differentiation while the latter gives color vision.
The essential function of the eyes is to visualize the object in front of us. But the visualization is facilitated by both cones and rods cells.
This article provides a comprehensive comparison and similarities between these photoreceptor cells. Take the time to read through it and find the crucial factors that provide distinction.
Comparison Table (Rods vs Cones)
Are photoreceptor cells responsible for vision in dim light or at night
Are photoreceptor cells responsible for vision in the daytime or bright light
Found at the periphery of the retina in an ample amount.
Found at the center of the retina but in a low amount.
Number in Retina
125 million rods.
5 million cones.
Number of Color Vision
Black and white
Several color visions like red, green, and blue
Respond Light Speed
Relatively low since they share neurons with the brain.
Comparatively high since each cell has its neurons.
Has a cylindrical shape.
Has a conical shape.
Convergence of retinal pathways
Sensitivity to wavelength
Sensitive – 480nm
Insensitive – greater than 640nm
Sensitive – 420nm, 534nm, 563nm
Concentrated in the fovea.
A single photon of light
A large number of protons
What Are Rods?
Rods are photoreceptor cells that support vision during dim light or at night. They are usually located at the periphery of the eye and they occur in plenty amount.
Rhodopsin is the main pigment found in the rods and it is responsible for night vision. Rods are said to be light-sensitive.
Rod cells are also said to have scotopic vision which implies that they perform well during dim light or at night. People with a low amount of rods usually experience night blindness.
What Are Cones?
Cones are photoreceptor cells that support vision during the day or bright light vision. These cone cells are a small amount when compared to rods.
The good news about cones is that an individual is able to differentiate between colors. Therefore, cones occur in three forms such as green, blue, and red. They are also less sensitive to light.
Iodopsin is the violet pigment present in cones and is responsible for violet vision. Cones tend to experience photopic which means eyes are able to visualize under bright light.
People with a low amount of cones normally experience colorblindness. Hence they are unable to differentiate between colors.
Main Differences between Rods and Cones
- Rods are responsible for vision in dim or night light while cones are responsible for vision in bright or daylight.
- Rods are located around the periphery of the retina whereas cones are located at the center of the retina.
- Cones have conical shapes while rods have a cylindrical shape.
- Rods are quite sensitive to scattered and direct light while cones are quite sensitive to direct light only.
- Rod cells tend to be narrower while cone cells are wider on the other hand.
- Human eyes have plenty of rod cells as compared to cone cells.
- Rod cells with deficiency rhodopsin cause night blindness while cone cells with insufficient iodopsin cause color blindness.
- Cone cells provide color vision in the form of red, green, and blue while rod cells do not provide any color vision apart from black and white.
- Rod cells have higher regenerative power as compared to cone cells.
- Rods occur in an ample amount while cones in less amount since they perform different duties.
Similarities between Rods and Cones
- Both are photoreceptor cells
- Both absorb light at a different wavelength
- Both are modified nerve cells
- Both are synapse with bipolar cells
- Both experience phototransduction
- Both cells possess membrane invaginations
- The chemical process that supports phototransduction
Frequently Asked Questions
- Why Are Rods More Sensitive than Cones?
Rods require less light to function than cones. Therefore, they are about 100 times more sensitive to a single photon than cones.
- Do We Have More Rods or Cones?
Rods are more than cones on the retina. There are about 120 million rods on the retina which makes them more sensitive than cones.
- How Do Rods and Cones Work?
Rods work at a very low light hence suitable for night vision. Cones work at a very high light hence suitable for daytime vision. Cones can be used to see more colors.
- Do Cones See Color?
Absolutely. The cones tend to use a lot of light and help in distinguishing different colors. Cones are divided into blue, green, and red. The human eye has about 6 million cones for color and daytime vision.
- Can Rods and Cones Regenerate If Damaged?
Before the retina cells die, rods and cones can be regenerated. But in case of nerve damage, the eye photoreceptors, rods, and cones will not regenerate.
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Both rods and cones in the eye perform different tasks besides both of them being photoreceptors. The rods and cones diagram above helps to clarify their location in the human or animal eye.
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