Evaluation and Fitting of Contact Lenses
For years, more and more people have been switching to contact lenses. Contact lens technology has evolved rapidly and with today’s variety of contact lenses, there are lenses for just about everyone. Switching from eyeglasses to contact lenses begins with an eye exam for contact lenses. After the contact lens exam comes a separate contact lens fitting session.
Start with the Eye Exam for Contact Lenses
Before anything else, you should have a comprehensive eye exam for contact lenses. During this contact lens exam, your eye doctor will check your vision and write a prescription for corrective lenses. This is the same type of prescription you would get for eyeglasses. He or she will also check for any eye health problems or other issues that may cause problems with contact lens wear.
After the contact lens exam, the next step is a contact lens consultation and contact lens fitting.
The Contact Lens Fitting
With so many contact lens choices, the first part of the consultation is a discussion with your eye doctor about your lifestyle and preferences regarding contact lenses. One choice that today’s contact lenses allow you to make is whether you want to change your eye colour. Different eye colours are available with contact lenses.
Other options include whether you want contact lenses that are designed to be replaced daily or those which can be worn for more extended periods. Most people choose soft contact lenses for their ease and comfort. However, there are also advantages of hard or what are called rigid gas permeable (GP) lenses. All the specifics will be discussed prior to your contact lens fitting.
Believe it or not, if you need bifocals, you can even opt for multifocal contact lenses or monovision (a prescribing technique where one contact lens corrects your distance vision and the other lens corrects your near vision). Once you have determined the type of contacts you want, the next step is the actual contact lens fitting.
Taking Measurements
During the Contact Lens Fitting
While it may not be apparent, our eyes come in different sizes, and one contact lens size doesn’t fit all eyes. If the curvature of a contact lens is too flat or too steep for your eye’s shape, it could lead to discomfort or even damage to your eye. Your eye doctor will take measurements and determine the best contact lens size and design for your eyes.
Here are some of the ways he or she will measure your eyes:
Corneal curvature
The eye doctor uses an instrument called a keratometer to measure the curvature of your eye’s clear front surface (cornea). This measurement helps your doctor select the best curve and diameter for your contact lenses.Your eye’s surface may be somewhat irregular because of astigmatism. But do not worry if this is the case, you can still get special contact lenses known as a “toric” contact lens. There are many brands of both hard and soft toric lenses, which are available in disposable, multifocal, extended wear and colored versions.
Your eye doctor will also perform a detailed mapping of the surface of your cornea (called corneal topography.) Corneal topography provides precise details about the surface of your cornea and creates a surface “map” of your eye, with different contours represented by varying colours.
Pupil and iris size
The size of your pupil and iris (the colored part of your eye) is important in determining the best contact lens design for you, especially if you are interested in hard lenses. These measurements are taken with a lighted instrument called a biomicroscope (also called a slit lamp) or simply with a hand-held ruler or template card.
Tear film evaluation
In order to wear almost all types of contact lenses, you must have an adequate tear film to keep the lenses sufficiently hydrated. Your eye doctor will place a liquid dye on your eye so your tears can be seen with a slit lamp. He or she may also use a small paper strip placed under your lower lid to see how well your tears moisten the paper. If you have a condition known as dry eyes (eyes that do not tear enough), most contact lenses will not work for you. If you produce some tearing, there are certain contact lens choices that you may be able to wear without a problem.
A Contact Lens Fitting Usually Results in Trial Lenses
No matter how comprehensive the eye exam for contact lenses, most eye doctors will give you a set of trial lenses just to confirm that they are the right choice for your eyes. With lenses in place, your doctor will use the slit lamp to evaluate the position and movement of the lenses as you blink and look in different directions. You will also be asked how the lenses feel.
Most people wear trial lenses for at least 15 minutes so that any initial excess tearing of the eye stops, and your tear film stabilizes. Then, you will learn about how to care for your lenses and how long to wear them. You will also receive training on how to put in and take out your new lenses. While it may seem difficult at first, most people quickly learn how to use contacts lenses.
Follow-Up Contact Lens Eye Exams
Your doctor may schedule a follow-up visit so he can confirm the lenses you chose are fitting your eyes properly and that your eyes are able to tolerate contact lens wear. A dye may be used to see if the lenses are causing damage to your cornea or making your eyes become too dry.
It is rare these days that contact lenses cause problems. But, with a follow up contact lens eye exam, your doctor will be able to detect any issues before they become big problems. Most problems that occur can be rectified by things such as trying different lenses or lens material, using a different lens care method, or adjusting your contact lens wearing time.
Your Prescription for Contact Lenses
After finding the right contact lenses, your doctor will write a contact lens prescription for you. This prescription designates the contact lens power, the curvature of the lens (called the base curve), the lens diameter, and the lens name and manufacturer. In the case of GP contact lenses, additional specifications are included in the contact lens prescription.
