How to Fit a Contact Lens

Contact lenses are designed to sit on the front of the eye, called the cornea. Each persons eyes have unique curves, and the lenses must be fit accurately to match the curve of each eye. Contact lenses are made from soft and rigid material and can be used to correct different types of vision problems or can be worn without a prescription to cosmetically change eye color. Precise measuring and rechecking of the fit of contact lenses is a must.

Instructions

1

Use the prescription from the refraction, or eye exam, to calculate the strength of the distance power of the contact lens for each eye. This number is written as plus for farsighted or minus for nearsighted and indicates the amount of correction needed in the lens. Spectacle and contact lens powers are not always the same because they depend on different factors, such as how far the glasses lens sits from the eye versus the contact lens that sits right on the eye, the shape of the eye and the type of lens.

2

Use a keratometer, the ophthalmic machine that measures the curvature of the eye, to obtain K-reading measurements. These numbers are used to determine the matching curves of the contact lens, called the base curve. Lenses must fit correctly to provide optimum vision and for the safety and health of the eye. If a lens does not sit properly on the eye, the contact wearer will not see well and the lens could cause damage to the cornea.

3

Evaluate the health of the eye. Use a slit lamp, a biomicroscope that allows you to see the cornea and eye up close. Check to make sure the eye has enough tear production and is not too dry. Contact lenses need to be kept moist for movement and for the health of the eye. Special lenses can be prescribed for eyes that have too much dryness.

4

Use the slit lamp to determine that the cornea is free from any damage. A lens should not be put on an eye that has any type of damage, even minor. If there are any signs of irritation, wait to try on lenses until the eye heals.

5

Test a pair of lenses on the eyes if you determine that the eyes are free from damage and are healthy. Use sample lenses, also called trial lenses, that have a base curve, thickness and material that you determine are similar to those of the anticipated final prescribed lenses. Let the lenses rest on the eyes for 20 minutes to allow the lenses to adhere and tighten or loosen. Check the fit of the lenses after 20 minutes with the slit lamp.

6

Recheck the fit and vision of the prescribed lenses after the lenses have been worn for one to two weeks to make sure the lenses are sitting properly and that vision correction is good. Make any adjustments as necessary.