Lens is a very delicate piece of cuticle. It forms the outer surface of the eye bellow lens is a glassy body. Both of them form dioptric apparatus of the eye. Their function is to focus the rays of light on to the sensory layer called as retina. The cells of the glassy body builds lens by secretion so they are known as lentigen cells.

Structure of lens:

The lens is stretchy and its curvature is controlled by ciliary muscles through zonules. One can easily change the curvature of the lens and can focus the eye on object at different distances. When focal distance is high, ciliary muscles are relaxed turning lens thick and resulting into high refraction.

To change focus to an object at different distances lens are stretched by ciliary muscles which reduces refractive index and hence increases focal distance. Growth of lens continues all through a life, by replacing new cells over old cells resulting in stiffer lens. As the age of person increases his accommodation, ability decreases.

The lens contains transparent proteins that are known as crystallins double in concentration than that of intracellular proteins. Crystellins are the reason for refractive properties of lens allowing most of the light to pass through it. Proteins are set in 20,000 thin concentric layers, having refractive index varying from 1.406 down to 1.386.

The lens is included in the capsular bag. If you glance through exocuticle, you will get an notion of microfibrils having its own structure. These cuticles derive their strength from fibrillar molecules. There are lamellae, plates in which the fabrills are parallel to each other but somewhat different angle from those in adjacent lamella.

Lens is multilayer structure. In youngsters, it is normally perfectly clear and stretchy. However, by the age its elasticity decreases, it becomes gloomy this condition is known as cataract. When cataracts become very stern then best way the lens should be replaced with artificial lens but they are not capable of accommodation. Lens performs important function of focusing without which one will not be able to visualize anything that comes his way so it's necessary to understand its structure.