Anatomy of the Eye 

Basic gross structure of the Eye

The pupil is the opening that allows light to enter the eye and reach the retina, it appears dark because of the light-absorbing pigments in the retina. The pupil is surrounded by the iris, whose pigmentation provides what we call the eye's colour. The iris contains two muscles that can vary the size of the pupil; one makes it smaller when it contracts, the other makes it larger. The pupil and iris are covered by the glassy transparent external surface of the eye, the cornea. The cornea is continuous with the sclera, the "white of the eye," which forms the tough wall of the eyeball. The eyeball sits in a bony eye socket in the skull, also called the eye's orbit. Inserted into the sclera are three pairs of extra-ocular muscles, which move the eyeball in the orbit. These muscles normally are not visible because they lie behind the conjunctiva, a membrane that folds back from the inside of the eyelids and attaches to the sclera. The optic nerve, carrying axons from the retina, exits the back of the eye, passes through the orbit, and reaches the base of the brain near the pituitary gland. 

Advanced  anatomy of the eye

•  The eye ball, is a shere of about 24mm in diameter with three principle components three layers (tunics) that form the wall of the eyeball; optical components that admit and focus light; and neural components, the retina and optical nerve. The retina is not only a neuronal component but also part of the inner tunica. The cornea is part of the outer tunic as well as one of the potical components. The three tunics of the eyeball are as follows:
• The outer fibrous layer (tunica fibrosa), is divided in two regions: the sclera  and cornea. The sclera (white if the eye) covers most of the eye surface and consists of dense collagenous connective tissue perforated by blood vessels and verves. The cornea is the treansparent region of modified sclera that admits light in to the

Image taken from wikipedia: https://iei.ico.edu/images/anatomy.jpg

• The middle vascular layer (tunica vasculosa), also called the uvea, because it resembles a peeled grape in fresh dissection. It consists of three regions: the choroid, ciliary body and iris. The choroid is a highly vascular, deeply pigmented layer of tissue behind the retina. It gets its name from a histological resemblance to the chrion of the pigment uterus. The ciliary body, a thickened extension of the chorid, forms a muscular ring around the lens. It supports the iris and lens and secretes a fluid called the aqueous humour. The iris is an adjustable diaphragm that controls the diameter of the pupil, its central opening. The iris has two pigmented layers. One is posterior pigment epithelium that blocks stray light from reaching the retina. The other is the anterior border layer, which contains pigmented cells called chromatophores. High concentrations of melanin in the chromatophores give the iris a black, brown or hazel colour. If the melanin is scanty, light reflectds from the posterior pigment epithelium and gives the iris a blue, green or gray colour.
• The inner layer (tunica interna) consistes of the retina and optic nerve.

 Fovea

The fovea is also known as the fovea centralis and is part of the eye, located in the center of the macula region of the retina.

• The fovea is responsible for sharp central vision (also called fovea vision), which is necessary in humans for reading, watching television or movies, driving, and any activity where visual detail is of primary importance.
• The fovea is surrounded by the parafovea belt, and the perifovea outer region: the parafovea is the intermediate belt where the ganglion cell layer is composed of more than five rows of cells; as well as the highest density of rods; the perifovea is the outermost region where the ganglion cell layer contains two to four rows of cells, and is where visual acuity is below the optimum.
  

Read more information at https://en.wikipedia.org/wiki/Fovea