The eye of the vertebrate eye contains a number of highly specialized tissues and cell types that also includes the transparent cornea and lens, the ocular vasculature and the retinal pigment epithelium. The eye is a spherical organ which is made up of tough, collagen-rich outer layer called corneoscleral coat. The opaque, white sclera of the eye merges with the clear cornea anteriorly that along with the crystalline lens of the eye helps to focus the light upon the retina. Cornea is transparent due to the regular order of its collagen fibrils, maintained by ion pumps present in its posterior layer. If this layer get injured then it may causes corneal oedema, clouding or visual loss.
The shape of the eye is maintained by regulation of its intraocular pressure (IOP), which is normally around 15 mm Hg. This pressure is achieved by a balance between aqueous humour formation and drainage through the trabecular network. Entry of light into the eye is determined by pupil size, which is controlled by the muscular actions of the iris. Constriction of the pupil is done by parasympathetic stimulation of the iris sphincter, while dilatation is done by sympathetic stimulation of the dilator muscle. The amount of light entering the eye determines the size of the pupil. Behind the iris, the lens is present which is used to adjust the refractive power of the eye. Contraction of the parasympathetically ciliary muscle make the lens curved and helps in the accommodation of near objects.
Last date updated on November, 2020