Scleral ring
The scleral ring (also sclerotic ring) is a hardened ring of plates, often derived from bone, found in the eye of animals in several groups of vertebrates. Mammals, amphibians, snakes, and crocodilians lack scleral rings. The ring is in the fibrous outer layer of the eye, called the sclera.
Scleral rings can be made of cartilaginous material (scleral cartilage) or bony material (scleral ossicles), or often a combination of both, that comes together to form a ring. The arrangement, size, shape, and number of ossicles vary by group. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical, or which live underwater.