Contents I. Introduction
The human eye is a sense organ that enables vision. The outermost layer of the eye is composed of cornea and sclera. The cornea is smaller in size and located in the front part of the eye. The sclera is the larger part and covers the rest of the eye. The cornea and the sclera are connected by a ring called limbus. The middle layer consists of the choroid, ciliary muscle, and iris. The innermost layer consists of the retina. It is not directly visible and can be viewed using an ophthalmoscope. The retina consists of an optic disc, macula, fovea, and blood vessels. The lens is located between the iris and the retina. The function of the lens is similar to that of a camera lens; the lens reflects the received light and is flexible and balances on the ciliary muscle. The ciliary muscle is triangular in shape and covers the vitreous body. The aqueous humour is filled in the anterior chamber and the posterior chamber. The posterior chamber is located between the iris, which forms the front portion of the eye [12], and the lens.
