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Difference between Rods and Cones

Rod Cells vs. Cone Cells

The Rod Cells and Cone Cells are both photoreceptor cells present in the eyes. These are sensitive receptors responsible for making vision possible altogether. They simply convert the light entering the retina into signals, and these signals are very potent as they change the complete membrane potential and enables the eyes to see. The resultant is called visual photo transduction. Therefore, the sole aim of these Rod and Cone Cells is to help the eyes fulfil their basic need, help it recognize the light waves, and convert them to signals which makes vision possible in humans and animals. The major difference between Rod Cells and Cone Cells is that the former enables one to watch in low light and the latter helps in the vision in bright light.

Difference Chart

Rod Cells Cone Cells
Sensitivity Rod Cells are very sensitive to low light. Cone Cells are very sensitive to bright light.
Structure Rod Cells are narrower than the Cone Cells. The Cone Cells are wider than the Rod Cells.
Location The Rod Cells are located at a very peripheral location in the retina. The Cone Cells are situated at the central location, which is also known as the fovea or the retina.
Quantity The normal human eyes have more number of Rod Cells. The number of Cone Cells is always less than that of the Rod Cells.
Contents The Rod Cells contain only a single type of visual pigment. The Cone Cells have three different kinds of visual pigments present in them.

Rod Cells

The Rod Cells are cylindrical shaped. These are photoreceptor cells present at the peripheral part of the retina which absorbs light in the form of photons and converts it to the signals which can be comprehended by the retina. There are about 120 million Rod Cells present in the eyes which make vision possible in the extremely low light as the Rod Cells are triggered by even the faintest of the light rays. These Rod Cells are very narrow in comparison to the Cone Cells, but at the same time, they are much more sensitive to light rays. This is the reason why they help us to see even in the very low light.

Cone Cells

The Cone Cells are a bit shorter photoreceptor cells which are located at the central part of the retina which is also called the fovea. The Cone Cells are present in a very less number in the retina, somewhat around 6 million cells and they are not very sensitive to light. They need the very high amount of light to trigger them and get into action. As they are sensitive to large quantities of light, the Cone Cells help in making the vision in bright light possible.

Key Differences

  1. The most basic difference between Rod Cells and Cone Cells is in the treatment they have towards low and bright light. Being triggered by different quantities of light, the Rod and the Cone Cells make it possible for the humans and animals to see in both low and bright light, respectively.
  2. The Rod Cells are located at a very peripheral position in the retina but the Cone Cells get the central location based on the conveniences to receive light.
  3. The structure of the Rod Cells and Cone Cells are very different. While the Rod Cells can be said to have a cylindrical shape, they are also longer and narrower. Cone Cells, on the other hand, are shorter in length and wider in their structure.
  4. The Rod Cells are also very heavily concentrated in the retina with their numbers reaching up to 120 million in the human eye. While the Cone Cells are very less, around 6 million in number which is quite a significant decrease from the number of Rod Cells.
  5. Only a single photon of light can trigger the Rod Cells and hence, it makes it possible for us to see even in low light conditions. The ability to see even in low light is called Scotopic Vision. But the Cone Cells require a very high number of photons to get triggered and this is why, it deals with the vision in bright light. And this capability is called the Photopic Vision.
  6. Rod Cells can detect all types of scattered and also the direct rays of light but the Cone Cells can detect and are sensitive to only direct light.
  7. The Rod Cells contain a single pigment known as rhodopsin but the Cone Cells have three different types of photopsin which can help in detecting the variations in the wavelength of light and thus in correct, precise vision.

Video Explanation

So, Rod Cells and Cone Cells are both photoreceptors but have certain huge differences. But at the same time, it cannot be denied that while the loss of Rod Cells can cause night blindness, the loss of Cone Cells will lead to permanent blindness.