The brille (also called the ocular scale, eye cap or spectacle) is the layer of transparent, immovable disc-shaped skin or scale covering the eyes of some animals for protection, especially in animals without eyelids. The brille has evolved from a fusion of the upper and lower eyelids. Brille is German and Norwegian for "glasses".
In snakes, there is no eyelid and the brille is clear and cannot be distinguished except when the animal is becoming ready for ecdysis. At that time, it becomes cloudy and is visible as a cover over the eye. When the snake moults, the brille is also shed as part of its skin. The Brilles protect their eyes from dust and dirt and gives them a "glassy-eyed" blank appearance.[1]
Snakes, flap-footed lizards, night lizards, and some skinks have brilles. All geckos except those in the subfamily Eublepharinae (eyelid geckos) possess brilles.
Fish also have transparent eyelids called adipose eyelids.