ABSTRACT
Three layers enclose the contents of the eye, the sclera, the choroid and the retina (Figure 1). The sclera is a thick, stiff, outer layer of connective tissue. At the front of the eye it becomes the cornea. At the back it becomes the dura mater covering the optic nerve. The sclera maintains the shape of the eyeball and provides attachment for the extraocular muscles. The curvature of the transparent cornea refracts incoming light and provides most of the focusing power of the eye. The choroid is a thin, highly vascular layer, dark brown in color because of the presence of choroidal pigment cells. By absorbing light it limits total internal reflection within the eye.
