The eyeball houses the retina —an extremely metabolically active layer of nerve tissue made up of millions of light receptors (photoreceptors)—and all of the structures needed to focus light onto it.
The eye is cushioned within the orbit by pads of fat. In addition to the eyeball itself, the orbit contains the muscles that move the eye, blood vessels, and nerves. The orbit also contains the lacrimal gland that is located underneath the outer portion of the upper eyelid.:background_color(FFFFFF):format(jpeg)/images/article/en/structure-of-the-eyeball/M8LpszX3BPX9CnZdVrL54w_enuCIS1bgMlrHcPHyAQ61A_Sclera_01.png){kind=logo}
These remarkable features of our eye are enabled by the complex structure of the eyeball. The eyeball consists of three layers; fibrous, vascular and nervous (retina). Functionally, the most important layer is the retina, which receives the external visual stimuli.