The prescription that you leave an eye exam with is typically spectacle specific – getting fitted for contacts involves different and additional processes. The contact lens of course sits on the eye and therefore it is common for a different power to be prescribed in comparison to your spectacles which sit a short distance in front of your eyes.
That being said, if you’re interested in wearing contacts, make sure you mention this to your optometrist, so that he or she can perform the extra measurements to determine what prescription you should be wearing with your contacts. Ensure you ask the question.
During a contact lens fitting, your optometrist will measure the curvature at the front of your eye using an instrument called a keratometer. This is important in determining the curve and size of your contact lenses. If your lenses are too flat or too steep it will not only be uncomfortable and affect the level of vision you get with them – it could also damage your cornea.
The keratometer only measures the central part of your cornea may also involve other measurements to enable your optometrist to see the curvature of your entire eye.
Contact lens fitting will also involve an evaluation of the tear film in front of your eye. If you have particularly dry eyes, for instance, contact lenses may not be the right solution for you. Alternatively, certain contacts are better choices for those with mildly dry eyes. Artificial tears can also be beneficial in moistening your eye. Your optometrist will be able to explain all of your options.
There are many different types of contact lenses available today from daily disposables that are hassle free to lenses that can be worn overnight on a continuous basis to conventional monthly disposable lenses. Not only can lenses today correct long and short sightedness but they can also correct astigmatism up to five dioptres of astigmatism.
Your optometrist will also use a biomicroscope, also known as a slit lamp, to evaluate the health of your cornea. This instrument magnifies your eye by up to forty times (40x) and provides your optometrist with a baseline with which to compare later on, and helps identify any problems which may affect your ability to wear contacts.
Finally, your optometrist will walk you through correct application and usage of contact lenses.
After you have been fitted for and selected an appropriate set of contacts, it is important to continue having your eyes checked regularly to ensure that they remain healthy.