Why Do Cats' Eyes Change Shape Three Times a Day?

It's often said that a cat's eyes change three times a day: round in the morning, linear at noon, and round again in the evening. This is a normal phenomenon and it happens because a cat's eyes adjust to changes in light conditions.

Why Do Cats' Pupils Constantly Change Shape?

1. A cat's pupils aren't static; they change in response to the intensity of daylight or artificial light. When light is strong, the pupils become narrow slits, while in dim light, they expand to become large circles. This explains why you might see round pupils in the morning and evening when light is less intense, and slit-like pupils at noon under bright sunlight. This adaptation allows cats to optimize their vision in various lighting conditions. These changes are due to the muscles around the iris that contract and relax.

2. Cats have very large pupils, and the muscles controlling these pupils are exceptionally strong. Their 'sphincter' muscles have an incredible ability to contract, allowing the pupil to change from a full circle to a very narrow slit. This quick contraction and expansion allows their eyes to quickly adapt to changes in light, which enhances their hunting ability and overall adaptability in various environments. This dynamic adjustment process is essential for their sharp vision in different lighting.

3. Unlike humans, cats cannot perceive a wide spectrum of colors. Their vision relies on only two types of cone cells, blue and green, limiting their color perception to mostly blue, green, and yellow shades. However, cats possess excellent night vision and a remarkable ability to detect motion. Their rod cells, which are responsible for low-light vision, are more abundant than in human eyes, giving them an advantage in darkness and the ability to perceive even the smallest movement. This combination of limited color vision but enhanced low-light and motion sensitivity makes their visual experience quite different from our own, but it’s perfectly adapted to their role as hunters.Source:5D Pet World