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Why do cat eyes shine? Science responds

Why do cat eyes shine? Science responds

June 1, 2022

Surely on some occasion we have seen a cat at night or in the dark, highlighting the brightness of their eyes especially when focused on some kind of light.

Although it is something that does not seem strange to us, It is likely that on some occasion we have wondered why this brightness , that have their eyes that make them shine in that way and if it helps them for something. In this article we intend to answer this question.

In fact, this is a question that has aroused the curiosity of man since antiquity, coming to be considered the guardians of the night and the underworld in ancient Egypt due to other aspects of that particularity. It was considered that the iridescence of his gaze during the night was due to the fact that they saw the truth and even beyond death, and that he kept the light of the sun in the world. But the brightness of a cat's eyes has a scientific explanation, the tapetum lucidum.

Why do cat eyes shine? The tapetum lucidum

The answer to why the eyes of cats shine is none other than the existence of a band of cells located behind the photoreceptors of the eyes of these animals, specifically between the retina and the optic nerve (it could be considered part of the choroids). Called tapetum lucidum, it acts like a concave mirror inside the eye, causing light entering through the pupil to pass through the retina both when entering the eye and when bouncing on the mat. A) Yes, the amount of light that is reflected in the retina increases greatly, and can even be perceived from the outside . Technically it is not that their eyes shine, but reflect the outside light.

This causes them to be able to capture and make the most of the ambient light, so that it is easier during the night to be able to move more easily than other creatures and can see in the dark as long as it is not total. His visual capacity increases greatly and serves as a deterrent against possible attacks.

The tapetum lucidum increases the sensitivity of the canes between thirty and fifty times, although this would not be enough to allow them to see in the most absolute darkness. In most animals without this adaptation, much of the visual information is lost because the eye does not reflect the totality of light entering through the pupil. In the case of cats, although there is some information loss such loss is much less thanks to the presence of the tapetum lucidum , which causes a much larger proportion of light to be retained in the retina and the eye canes can process much more information.

Not only cats

The tapetum lucidum is what causes the eyes of cats to shine in the dark, but it is a biological adaptation shared with other species. And is that cats are not the only creatures whose eyes shine during the night. We can observe the same effect in most species of cats and even in a large part of dogs. Also bats, sharks, horses, crocodiles or even cows own tapetum lucidum.

In general, these are animals with nocturnal habits, both at the level of predators and prey. And it is that evolution has generated structures of this kind to emerge in order that those beings that live and act mainly during the night or whose prey or predators have such habits can survive. However, mainly diurnal animals do not usually own it, such as humans and pigs.

Can it cause difficulties?

The tapetum lucidum has many advantages, but it could be thought that it can be a disadvantage in situations where there is a lot of light, such as during the day. But nevertheless, the vision of cats has other characteristics that allow them to adapt other difficulties .

Between them they have a pupil capable of contracting to unsuspected limits, contracting until reaching a narrow strip and managing to reduce the amount of light that enters the eyes when it is intense.

Bibliographic references:

  • Coles, J.A. (1971). Some reflective properties of the tapetum lucidum of the cat's eye J.Physiol .; 212 (2): 393-409.


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