The retina represents the innermost layer of the eye.
The retina, derived from the inner and outer layers of the optic cup, is the innermost of the three concentric layers of the eye (see Fig. 24.1c). It consists of two basic layers:  The neural retina or retina proper is the inner layer that contains the photoreceptor cells.
 The RPE is the outer layer that rests on and is firmly attached through the Bruch’s membrane to the choriocapillary layer of the choroid.
A potential space exists between the two layers of the retina. The two layers may be separated mechanically in the preparation of histologic specimens. Separation of the layers, “retinal detachment” (Folder 24.2), also occurs in the living state because of eye disease or trauma.
In the neural retina, two regions or portions that differ in function are recognized:  The nonphotosensitive region (nonvisual part), located anterior to the ora serrata, lines the inner aspect of the ciliary body and the posterior surface of the iris (this portion of the retina is described in the sections on the iris and  ciliary body).
 The photosensitive region (optic part) lines the inner surface of the eye posterior to the ora serrata except where it is pierced by the optic nerve (see Fig. 24.1).
The site where the optic nerve joins the retina is called the optic disc or optic papilla. Because the optic disc is devoid of photoreceptor cells, it is a blind spot in the visual field. The fovea centralis is a shallow depression located about 2.5 mm lateral to the optic disc. It is the area of greatest visual acuity. The visual axis of the eye passes through the fovea. A yellow-pigmented zone called the macula lutea surrounds the fovea. In relative terms, the fovea is the region of the retina that contains the highest concentration and most precisely ordered arrangement of the visual elements.
Layers of the Retina
Ten layers of cells and their processes constitute the retina.
Before discussing the ten layers of the retina, it is important to identify the types of cells found there. This identification will aid in understanding the functional relationships of the cells. Studies of the retina in primates have identified at least 15 types of neurons that form at least 38 different types of synapses. For convenience, neurons and supporting cells can be classified into four groups of cells (Fig. 24.9):  Photoreceptor cells—the retinal rods and cones  Conducting neurons—bipolar neurons and ganglion cells  Association neurons and others—horizontal, centrifugal, interplexiform, and amacrine neurons  Supporting (neuroglial) cells—Mler’s cells, microglial cells, and astrocytes
The specific arrangement and associations of the nuclei and processes of these cells result in the retina being organized in ten layers that are seen with the light microscope. The ten layers of the retina, from outside inward, are (Figs. 24.9 and 24.10).
1.
Retinal pigment epithelium (RPE)—the outer layer of the retina, actually not part of the neural retina but intimately associated with it 2.
Layer of rods and cones—contains the outer and inner segments of photoreceptor cells