The third eyelid is a tiny triangle of pinkish or whitish tissue that is sometimes visible in the corner of the cat’s eyes. It’s called the haw, or nictating membrane. Humans have something like it – the small pink bump at the inner corner of the eyes. In the cat, the haw rises automatically and then moves sideways across the eye to protect or lubricate its sensitive surface. If the cat is ill, undernourished, or on the verge of catching a disease, the presence of the haw is a good indicator that the cat’s health isn’t up to par. The spontaneous movement occurs because pads of fat behind the eyeballs, which act as shock absorbers, start to shrink when the cat is in poor health. This is usually a signal to immediately take your cat to a veterinarian.