If you’ve ever seen a cat’s eyes in the dark, they appear to glow.
Unlike humans who need artificial or moon light to see in the dark, cats can see using only 1/6 of the light humans require.
In low light cat’s pupils open very wide. In bright sunlight they are able to contract and protect the sensitive retina. Two shutter-like muscles allow the cat’s eyes to become slits in bright light.
All cats have elliptical-shaped pupils larger than a humans allowing more light into the eye. The curved lens helps the cat to focus more sharply.
There are two different light receptor cells on the retina, cones and rods. Cones are sensitive to high light levels, used to see color. Rods are sensitive to low light. The concentration of receptors is on a broader horizontal band than that of humans. This allows the cat to detect ground movement at great distance, finding prey more easily.
But what makes the cat’s eyes glow in the dark? In the back of the eyes is the tapetum lucidum which aids in increasing the amount of light hitting the retina. The tapetum lucidum is a layer of tissue lying just behind or in the retina. The tapetum lucidum acts like a mirror, reflecting light back to the sensor cells in the retina. The causes the cat’s eyes to glow when a beam of light shines on them.
And that’s what causes the cat’s eyes to glow.