How do eyes work and parts of eye?

Above Article Ad

Eye is a photo receptor organ or we can also say as the organ of sight. Photo receptor are responsive to changes in intensity or wavelength of eye. The structure of human eye is a spherical eyeball lodged in an orbit formed by the skull bones.

Article inline ad #1

It is protected by eyebrows and Eyelids are movable and have eyelashes. The eyelashes function is to protect eye from injury,dust or germs by regular blinking. There are six sets of muscles attached to the outer surface of eyeball which help to rotate it in different directions. Meiobomian glands secrete oily secretion to lubricate eyelids and eyelashes. The eyeball is formed of three coats or tunics and they are outer (sclerotic),middle (choroid) and inner (retina) layer. Sclerotic is the outer fibrous coat of eye ball and is formed of three parts- sclera,cornea and conjunctiva. Choroid is the middle layer which is vascular and pigmented and is formed of three parts- choroid, ciliary part or ciliary body and iris. And iris contains two types of muscles and they are circular muscles and radial muscles. At last retina is the inner layer which is highly photo sensitive and consists of two types of photo receptor cells i.e. rods and cones and also photosensitive elements such as bipolar neurons and ganglionic layers.

Lens is a large, flexible, transparent, biconvex and fibrous crystalline situated behind the iris. The lens separate the eyeball in two chambers i.e. aqueous chamber and vitreous chamber. Aqueous chamber is smaller chamber between cornea and lens whereas vitreous chamber is larger chamber between lens and retina. Eyes have the power of accommodation which helps to see objects situated at various distances. Iodopsin works in day light and artificial light. This pigment is sensitive to bright light and colors. Defects of eyes are hypermetropia(far slightness),myopia (short slightness), astigmatism, cataract (motibindu), glaucoma (jalbindu), presbyopia, conjunctivitis and trachoma.