Why does a cat have a film over its eyes when it sleeps? - briefly
When cats sleep, they often exhibit what appears to be a thin film or membrane covering their eyes. This phenomenon is due to the presence of the third eyelid, also known as the nictitating membrane. The third eyelid serves to protect and moisten the cat's eyes during sleep, ensuring that they remain healthy and well-lubricated.
Why does a cat have a film over its eyes when it sleeps? - in detail
Cats, like many other animals, exhibit a peculiar behavior during sleep: their eyes develop a thin, transparent membrane that appears as a film or third eyelid. This structure is known as the nictitating membrane or haw, and it serves several important purposes related to the cat's health and well-being.
Firstly, the nictitating membrane acts as a protective barrier for the cat's eyes. While sleeping, cats are vulnerable to environmental factors such as dust, debris, and potential irritants that could enter their eyes. The membrane provides an additional layer of defense, ensuring the eye remains moist and clean during sleep.
Secondly, the third eyelid helps maintain optimal eye health by distributing tears evenly across the surface of the eye. This continuous lubrication is essential for preventing dryness and promoting overall ocular health. The membrane also aids in the removal of any foreign particles that may have entered the eye, contributing to its natural cleaning process.
Moreover, the presence of the nictitating membrane can indicate the cat's emotional or physical state. In some cases, the appearance of this third eyelid might signal stress, illness, or discomfort in the cat. Veterinarians often check for signs of the membrane as part of a routine examination to assess the animal's well-being.
It is important to note that while the nictitating membrane is common during sleep, it can also be observed when cats are awake but experiencing stress or illness. In such cases, the presence of this third eyelid should prompt further observation and, if necessary, a visit to the veterinarian.
In conclusion, the film over a cat's eyes during sleep serves multiple critical functions, including protection from irritants, tear distribution, and indications of health status. Understanding this natural behavior provides valuable insights into feline biology and welfare.