What are contact lenses?

They are small thin disc-like plastic lenses of the desired power, worn in contact with the clear cornea of the eye.

What are the types of contact lenses?

I Hard plastic lenses

(a) Corneal lenses (covering part of the clear cornea)

(b) Scleral lenses (also termed haptic lenses, covering in addition to the cornea, part of the white of the eye)

II Flexible contact lenses

(a) Soft or jelly hydrophilic lenses

(b) Silicone lenses

Today's lenses are all made from a special plastic, be it hard or soft. Glass is never utilised, because of the danger from breakage.

Where are contact lenses worn? Why do they not fall off?

Contact lenses are worn on the clear cornea of the eye. They are held in place by surface tension.

What are contact lenses used for?

The most common reason is to correct errors of refraction like myopia or short-sight, hypermetropia or long-sight and astigmatism, for which spectacles are needed. Special types of lenses are also used for the correction of curvature defects of the eye like keratoconus and for correction of subnormal vision.

What specific eye defects can be controlled by using contacts?

Anisometropia: Here one eye has a very high power while the other eye is normal or has a low power. With spectacles it is impossible for the eyes to work together as the object size seen by the two eyes differs. Contacts restore binocular vision with normal object size.

Aphakia: A condition resulting after cataract removal. Contracts are ideal if one eye is operated upon, if binocular vision is to be achieved.

Keratoconus: or cone formation of the cornea, which bulges and becomes irregular. Spectacles are of no help. Only contacts are successful in this case for which the only alternative would be a risky corneal transplant.

Burnt and injured cornea with scars and irregularity: The irregular eroded surface of the eye is replaced by the optically perfect contact lens and excellent vision is achieved.

Can I decide what type of lens, soft or hard, I should wear?

Though you may express your desire for a particular type of lens it is best to let your doctor decide. On certain eyes, specially with high numbers, soft contact lenses are best. On the other hand, soft lenses are not suitable for eyes with astigmatism.