Contact lens

Contact lenses are used to correct errors of refraction such as

• myopia
• hyperopia (hypermetropia)
• astigmatism
• presbyopia

There are two types of lenses:

• hard lenses
  • most commonly used are rigid gas-permeable (RGP)
    • made of plastics, silicone or fluoropolymers
    • used for astigmatism
    • used to combat allergies
      • when tendencies to form protein deposits in lenses
  • soft lenses -commonest in use
    • many types
      • daily wear lenses
      • extended wear
        • lenses removed at least weekly for cleaning and disinfection
        • greater risk of corneal infection
      • disposable wear
        • recommended for allergies
        • toric soft contact lenses - astigmatism

Cautions to contact lens use include:

• frequent eye infections
• severe allergies
• dry eye that is resistant to treatment
• working in a dusty environment

Complications:

• complications associated with contact lenses
  • change in corneal physiology, leading to
    • epithelial,
    • stromal, and
    • endothelial compromise
  • lens deposition
  • allergic conjunctivitis
  • giant papillary conjunctivitis
  • peripheral infiltrates
  • microbial keratitis
  • neovascularization

Reference:

1. Sucheck JK et al. Contact lens complications. Ophthalmol Clin North Am. 2003 Sep;16(3):471-84.