In the anterior optic chamber there are placed (1) the anterior part of the lens (l1) and (2) the folds of the iris (Ir). The whole chamber, except the part formed by the lens, is lined by the epidermis (Int1 and Int2). Bounding the inner side of the anterior optic chamber is a layer which is called the choroid (Int1) which is continued anteriorly into the fold of the iris (Ir). The most superficial layer of the choroid is the epithelium already mentioned, next comes a layer of obliquely placed plates known as the argentea externa, then a layer of muscles, and finally the argentea interna. The argentea interna abuts on a cartilaginous capsule, which completely invests the inner part of the eye.
The lens is a nearly spherical body composed of concentric lamellæ of a structureless material. It is formed of a small outer (l1) and large inner (l) segment, the two being separated by a thin membrane. It is supported by a peculiar projection of the wall of the optic cup, known as the ciliary body (Co.ep), inserted at the base of the iris, and mainly formed of a continuation of the retina. This body is however muscular, and presents a series of folds on its outer and inner surfaces, which are especially developed on the latter.
The membrane dividing the lens into two parts is continuous with the ciliary body. Within the lens is the inner optic chamber, bounded in front by the lens and the ciliary body, and behind by the retina.
The retina is formed of two main divisions, an anterior division adjoining the inner optic chamber, and a posterior division (N.S) adjoining the cartilage of the choroid. The two layers are separated by a membrane. Passing from within outwards the following layers in the retina may be distinguished:
Anterior division of retina.
(1) Homogeneous membrane.
(2) Layer of rods.
(3) Layer of granules imbedded in pigment.
Posterior layer of retina.
(4) Cellular layer.