(An image by Nikolay Lamm showing us what the world would look like through the eyes of a cat)
Artist Nickolay Lamm's latest project offers photos comparing cat vision with human vision. Cats have a wider visual field than humans - 200° visual field compared to the human’s 180°. Cats also have a 30° range of peripheral vision, vision outside the centre of their gaze, compared with the human’s 20°. This is so that they can see their prey at the corner of their eyes. Compared to the human retina, the feline retina has six to eight times more rod cells. As light receptors that are sensitive to and function best in low light, rod cells play an important role in night hunters like cats. Cats need to be able to sense the movement of their prey in very low light. This explains why they have so many rod cells in cats compared to humans. Cats have a tapetum lucidum with a function associated with the rod cells. Tapetum lucidum is a reflective layer behind the retina which directs light passing through it back to the rod cells of the retina, which, being sensitive to low light, enable cats to see in the dark when there isn’t much light available. Tapetum lucidum is also what gives those glowing eyes of your cats in photos.
(Another image from Nikolay Lamm's collection)
Lancaster University has developed a camera based on this mechanism. The camera is able to see radiation emitted by nuclear reactors. It uses a detector with a liquid that lights up when exposed to fast, energetic neutrons or gamma rays. The detector is positioned behind a slit-shaped tungsten collimator- a device that aligns a beam of particles or waves to a specific direction. This is similar to cat eyes, and stops the detector from becoming saturated (like when an image is over-exposed) by high-intensity nuclear emissions. The camera is then moved around and rotated on its axis so that the rate of detection at different angles allows researchers to determine the exact source of radiation. Real-time data from cameras can provide crucial information about the condition of the nuclear reactor, increasing the safety of nuclear power plants.
Cones are light receptors that have an opposite role to the rod cells. They function best in bright light, and understandingly, cats have less cones than humans do. This means that humans have better motion detection in bright light than cats. Another aspect of having more cones is that human vision has greater resolution, and we can see objects from 20 feet away where cats can only see it from 100 feet away. More cones mean humans can see a greater range of vibrant colours, whereas cats can’t see red, orange or brown. They can however see blue and yellow. Cats are able to distinguish colours near the blue end of the spectrum better than colours near the red end.
Cats’ pupils open very wide in dim light, but contract to a tiny slit in very bright light. This is to protect the sensitive retina and to improve the eyes’ ability to produce clear images at different distances from the cat, called the depth of field.
Cats also don’t need to blink their eyes to keep their eyes lubricated with tears, which is useful for hunting because they can be on a constant lookout for their prey. Cats can however, ‘squint’ to express affection and ease around other creatures.