If your dog is sporting a red bump in the corner of their eye, it’s likely cherry eye, a concerning but not uncommon experience for many dog owners.
Unlike humans who only have two eyelids, dogs have three. The third eyelid, called the nictating membrane, arises from the inner corner of the eye and covers the eye diagonally lubricating it, so it is important to maintain the function of this gland.
Cherry eye in dogs occurs when this third eyelid gland prolapses. Luckily, the symptoms of cherry eye are easy to notice and if treated quickly, there are usually no long-lasting effects. If ignored, surgery may be required to treat cherry eye in dogs in order to prevent permanent long-term eye problems like decreased tear production.
via Whisker Therapy