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Soft contact lens: These are well flexible lenses made of a polymer called HEMA (Hydroxy
Ethyl Metha Acrylate). They are very comfortable to wear and permit oxygen to reach the
cornea.

Semi soft lenses or Rigid Gas Permeable Lenses: These lenses are made from special
materials like Cellulose or Silicon acrylate. They are less flexible than soft contact lenses
but allow some oxygen to pass through the cornea. Though less comfortable than soft

lenses, they can be used to correct steep corneas and high astigmatism.
Hard contact lenses: Made of a polymer called PMMA (Poly Methyl Metha Acrylate), hard
lenses are least flexible and permit almost no oxygen to pass through to the cornea. The

advantage of a hard contact lens is its durability.

Advantages of a contact lens:
• A contact lens provides a larger field of vision than spectacles and a better range of

mobility. Hence it is ideally suited for sportspersons and people engaged in outdoor
physical activities.
• In people with high refractive error in one eye alone, spectacles will produce double
vision due to the image size discrepancy. Contact lenses can be used for such people.
• Cosmetically, they offer an advantage over spectacles.
• Apart from correcting refractive errors, contact lenses are also used to deliver drugs to
the eyes and to treat corneal diseases.
• Nowadays contact lenses are also available in various colors and can be used by people
even with normal vision for the cosmetic appeal.

Precautions

With all these advantages, there are also some precautions to be taken before opting for
contact lenses.
• An ophthalmologist should examine the eyes to rule out infections and other disorders
of the eye.
• A qualified contact lens specialist alone should do the contact lens fitting. This includes
measuring the corneal curvature and diameter and issuing a suitable pair of contact
lens. After wearing them, the specialist examines the eyes for a good, comfortable fit
on the eyes.
• Hand washing with soap before inserting and removing the contact lens from the eye
is mandatory.
• Proper maintenance of the contact lens by cleansing it with the appropriate lens fluid

is necessary.
• If the eyes are red or there is a white discharge from the eyes, the contact lens should

not be used and the eye care professional should be contacted for further instructions.

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