Casey Eye Institute at OHSU, Portland, Oregon

Where Healing, Teaching and Discovery Come Together

Improving Vision with Contacts

Contact lenses are worn directly on the cornea of the eye. Like eyeglasses, contact lenses help to correct refractive errors. They do this by adding or subtracting focusing power to the eye's cornea and lens.

Facts About Contact Lenses

Almost 25 million Americans wear contact lenses. About half of these people use daily wear soft lenses. Currently, there are five types of contact lenses in use:

  • Original "hard" lens
  • Soft, water-absorbing lens
  • Rigid gas-permeable lens
  • Other rigid lenses
  • Flexible, non-water absorbing lenses

Reading a Contact Lens Prescription

The prescription for contact lenses includes more information than a prescription for glasses. Special measurements are taken of the curvature of the eye. In addition, your doctor will determine if your eyes are too dry for contact lenses, or if there are any corneal problems that may prevent you from wearing contact lenses. Trial, or diagnostic lenses are usually tested on the eyes for a period of time to ensure proper fit.

A contact lens prescription usually includes the following information:

  • Specific name (like the make and model) of the contact lens
  • Contact lens power (measured in diopters, like eyeglasses)
  • Contact lens base curve
  • Diameter of the lens

Learn about our Contact Lens service at the Casey Eye Institute.