All dogs have a third eyelid that contains the tear gland and is called the nictitans. In some dogs, the connective tissue holding this into place is too weak and will allow the gland to pop out of place. This will look like a small red mass in the corner of one or both eyes. This is not a painful condition but it the gland remains out of place too long, it can become infected or inflamed. Surgery may be required in some cases to repair the placement of the gland.