Many times in life, One-size-fits-all can be really great! It takes the stress out of finding the right fit and is often quick, easy and convenient. But when it comes to contact lenses, one-size-fits-all is not only an uncomfortable, but also a potentially damaging, concept that can result in serious vision and eye issues. Contact lenses generally sit directly on the cornea, making it very important that the measurements of your contact lenses are 100% accurate to ensure a comfortable, healthy fit. This will prevent eye infections and other eye conditions such as corneal abrasion, a painful scratch on the surface of the eye that can make even blinking uncomfortable!
Switching from glasses to contacts or changing your contact lens prescription are processes best overseen by an eye care professional that will measure your eyes properly and find the best fit for you. Below, Dr. McGee walks us through some of the most important parts and points of proper contact lens measurements and fitting.
Each person's eyes are just a little bit different. Some corneas are steep, while others are shallow. Some people have mild astigmatism, while others' astigmatism is more severe, and yet others don't have at all. All these considerations and more make proper corneal measurements a very important starting point. Your eye’s curvature will first be measured using a measuring device known as a keratometer. This is a very simple procedure, in which you simply rest your chin on a support while the instrument takes photographs of your eye. These photographs are used to analyze reflections of light from your cornea to help the doctor determine the exact curvature of your eye and the size of contact lens that you will need.
In a case in which a patient has a hard-to-fit cornea, based on an unusual curvature of the eye, further computerized measurements are often taken using corneal topography, allowing a more precise picture of the shape of the corneal surface.
With astigmatism the surface of the eye is irregular and causes poor focusing. In this case toric contact lenses, which are made specifically to correct the distortions of the eye caused by astigmatism and requires more detailed measurements than a standard lens.
It is also important to get an accurate measurement of the pupil, the opening at the front of the eye where light enters, as well as the colored part of the eye, the iris. This is measured either with a ruler or with an automated device.
Your eye doctor may also perform a tear film evaluation in order to assess if you are prone to dry eyes. If you are, your eye doctor may be able to prescribe you specialty lenses that help keep the eye properly hydrated and prevent dry eye symptoms such as red, itchy, uncomfortable eyes.
After completion of all the required measurements, your eye doctor will know what type and shape of contact lens you require. Many doctors give their patients a trial pair of lenses to try on at this point. An instrument called a biomicroscope may be used for a magnified view of the cornea with the contacts in, to assess the fit. This same instrument can also be used to detect and assess any change in the health of your eyes after beginning contact lens wear. You are likely to also have a number of follow-up visits after the initial fitting. These visits are meant to ensure that your eyes are remaining healthy with contact lens use. Your doctor should be able to order your permanent prescription after the second or third visit, assuming that he or she has not seen any damage to your eyes from the trial pair and has confirmed that the fit is proper.
It is important that your lenses be properly fitted to your eyes for maximum comfort and health at all times. For more information, contact your eye doctor today.