Human Eye Lens

The eye lens of humans is transparent and crystalline. It is biconvex and responsible for focussing light on the retina. It is present behind the cornea and attached to the ciliary body by ligaments.

The main characteristics of humane lens are:

The lens is nourished by the aqueous humour, and is bathed in both the vitreous body and aqueous humour, however, it lacks blood vessels.

The lens is transparent, ellipsoidal, crystalline, and biconvex, with the posterior part being more curved than the anterior part.

The ciliary body is held in place by ligaments.

The iris covers the anterior portion of the lens. It is an extension of the ciliary body that is pigmented and controls the amount of light that passes through the lens.

The pupil is the aperture of the lens surrounded by the iris.

The ciliary muscles alter the shape of the lens and regulate the focus of the lens. The capacity of the lens to adjust and focus on objects located at different distances is referred to as accommodation.

The lens capsule is the outermost transparent layer of the lens.

The major portion of the lens is composed of lens fibre cells, which are elongated and transparent.

The lens epithelium is present between the capsule and fibres at the anterior portion, composed of simple cuboidal epithelium. This epithelium is responsible for generating new lens fibres.

90% of proteins within the lens are composed of water-soluble proteins called crystallins.

Diseases of the Human Eye Lens

Presbyopia – It occurs with aging and is caused by a decrease in the flexibility and thickening of the eye lens. As a result, the lens’s ability to change its shape to focus on objects that are close decreases with age.

Cataract - It is a condition in which the eye lens becomes cloudy, resulting in blurred vision.

Ectopia Lentis - It is a condition that is caused by the displacement of the eye lens.

Aphakia - This condition refers to the absence of the lens in the eyes.

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