Why does a cat have its third eyelid closed? - briefly
A cat's third eyelid, also known as the nictitating membrane, may be closed due to various reasons. This can include illness, injury, or even as a normal response to certain stimuli.
Why does a cat have its third eyelid closed? - in detail
The third eyelid, also known as the nictitating membrane or haw, is a transparent or translucent membrane that can be observed in the inner corner of a cat's eye. This structure is not unique to cats; it is present in many other animals, including birds, reptiles, and some mammals. The primary function of the third eyelid is to provide additional protection to the eye. It can close partially or fully to shield the eye from debris, dust, and potential injuries, ensuring that the cornea remains clean and undamaged.
There are several reasons why a cat's third eyelid might be closed or more visible than usual. One of the most common reasons is irritation or inflammation of the eye. This can be caused by a variety of factors, including infections, allergies, or foreign objects lodged in the eye. When the eye is irritated, the third eyelid may become more prominent as it attempts to protect the sensitive cornea from further damage. Additionally, the third eyelid can be a sign of dehydration or systemic illness. Dehydration can cause the tissues around the eye to shrink, making the third eyelid more visible. Systemic illnesses, such as kidney disease or hyperthyroidism, can also lead to changes in the appearance of the third eyelid.
In some cases, the third eyelid may be closed due to a condition known as "cherry eye." This occurs when the gland associated with the third eyelid prolapses, causing it to protrude from the eye. Cherry eye is more commonly seen in certain breeds of dogs but can occasionally affect cats as well. This condition typically requires veterinary intervention to correct.
Another potential cause is a condition known as Horner's syndrome. This neurological disorder affects the nerves that control the muscles around the eye, leading to the third eyelid appearing more prominent. Horner's syndrome can be caused by various underlying issues, including trauma, tumors, or other neurological problems.
It is essential to monitor a cat's third eyelid for any changes, as it can be an early indicator of underlying health issues. If a cat's third eyelid is consistently closed or more visible than usual, it is advisable to consult a veterinarian. The vet can perform a thorough examination to determine the underlying cause and recommend appropriate treatment. Early detection and intervention can prevent potential complications and ensure the cat's overall well-being.
In summary, the third eyelid in cats serves a protective function, shielding the eye from potential harm. When it is closed or more visible, it may indicate irritation, dehydration, systemic illness, cherry eye, or Horner's syndrome. Regular veterinary check-ups and prompt attention to any changes in the third eyelid can help maintain a cat's ocular health.