Layers of the eyeball

The eyeball consists of three distinct layers. From superficial to profound, they include:

  • The fibrous layer or the outer layer consists of the sclera and cornea. The sclera is a white outer layer that surrounds the posterior 5/6 of the eyeball. The sclera also can be divided into three layers: the episclera, the scleral stroma, and the lamina fusca. The cornea is a transparent layer surrounding the anterior 1/6 of the eyeball. The cornea is continuous with the sclera.
  • The vascular pigmented layer is the middle layer, also called the uvea. This layer is rich in blood vessels and pigment. The vascular pigmented layer has three parts that are connected with each other. These parts are the choroid, ciliary body, and iris. The ciliary body produces the aqueous fluid. The iris contains the pigment that determines the eye colour. In the middle of the iris is a hole called the pupil.
  • The nervous layer or the retina is the deepest layer. The retina can be further divided into two layers: pigmented or outer layer and neurosensory or inner layer. The retina is the light-sensitive structure of the eye, where the neural visual pathway begins. The neural retina contains three layers of neural cells: light-sensitive photoreceptor cells, bipolar cells, and ganglion cells of the retina. The retina is continuous with the optic nerve.