The document classifies contact lenses based on their anatomical position as scleral lenses covering the cornea and sclera, semiscleral lenses covering the cornea and partially the conjunctiva, or corneal lenses conforming to just the cornea. It also categorizes lenses based on their material as rigid non-gas permeable PMMA lenses, RGP cellulose acetate butyrate or silicone lenses, or soft hydrogel HEMA lenses. Lenses are further divided by mode of wear as daily wear, extended wear, or disposable lenses and by water content as low, medium, or high.

1. Contents:
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Anatomical position
Nature of material
Mode of wear and water content

2. Depending upon the anatomical position
occupied:
Contact lenses have been variously classified as follows:
1. Scleral contact lenses:
These lenses cover cornea
and conjunctiva overlying
the sclera.
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3. Cont…
2. Semiscleral contact lenses:
These lenses cover cornea and bridge the limbus to lie
partially on the conjunctiva.
3. Corneal contact lenses:
These lenses confirm to the cornea.
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4. Depending upon the nature of material
used:
 1.Rigid non gas permeable contact lenses , for example those
made up of PMMA.
 2.RGP lenses, for example cellulose acetate butyrate (CAB) and
silicone lenses.
 3.Soft contact lenses, or the hydrogel contact lenses, for
example those made up of HEMA.
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5. Depending upon the mode of wear:
 Daily wear contact lenses.
 Extended wear contact lenses.
 Disposable contact lenses.
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6. Depending upon the water content:
 1. Low water content (0%-40%).
 2. Medium water content (40%-55%).
 3. High water content (>55%).
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