contact lens use Indications & Contraindications

Indications of contact lens use

1. Optical indications include anisometropia, unilateral aphakia, high myopia, keratoconus and irregular astigmatism. Optically they can be used by
every patient having refractive error for cosmetic purposes.

Advantages of contact lenses over spectacles:
(i) Irregular corneal astigmatism which is not possible to correct with glasses can be corrected with contact lenses.

(ii) Contact lenses provide normal field of vision.

(iii) Aberrations associated with spectacles (such as peripheral aberrations and prismatic distortions) are eliminated.

(iv) Binocular vision can be retained in high anisometropia (e.g., unilateral aphakia) owing to less magnification of the retinal image.
 

 (v) Rain and fog do not condense upon contact lenses as

Types of contact lenses

Depending upon the nature of the material used in
their manufacturing, the contact lenses can be divided
into following three types:
1. Hard lenses,
2. Rigid gas permeable lenses, and
3. Soft lenses.

1. Hard lenses are manufactured from PMMA
(polymethylmethacrylate). The PMMA has a high
optical quality, stability and is light in

CONTACT LENSES

what is contact lens

Contact lens is an artificial device whose front surface
substitutes the anterior surface of the cornea.
Therefore, in addition to correction of refractive error,
the irregularities of the front surface of cornea can
also be corrected by the contact lenses.
Parts, curves, and nomenclature for contact lens
To understand the contact lens specifications
following standard nomenclature has been recommended
(Fig. 1).

Fig. 1. A contact lens.

1. Diameters of the lens are as follows :
i. Overall diameter (OD) of the lens is the linear measurement of the greatest distance across the physical boundaries of