Maple Eye and Laser Center
Contact Lens Measurements | Correct Contact Lens Measurement

The Importance of Proper Contact Lens Measurements and Fitting

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Contact lenses remain one of the most popular treatment choices for patients who have refractive eye errors that require them to use prescription lenses to correct their vision. However, contrary to what some people, not all contact lenses are the same. There are various types available, as well as a range of sizes. The reason for this is because every patient’s eyes are unique.

Our eyes are extremely sensitive and can be irritated by the slightest thing. They are also easily damaged. Contact lenses sit directly onto the cornea itself, actually touching it. For this reason, your contacts must be a perfect fit. Nevertheless, a one-size-fits-all approach cannot and should not be used when it comes to contact lenses and trying to do so could result not only in poor vision but also considerable discomfort and in some instances, damage to your eyes. Patients also need to ensure that the contact lens remains stable on the surface of their eyes otherwise it could move around and affect the quality of their vision.

Why contact lens measurements are needed

Every patient is unique and so too are their eyes. Refractive errors occur because of the way that light enters and is processed by the eye. The responsibility for this task lies with the cornea, which is the clear, domed lens that covers the front part of the eye. The cornea is a little different in each patient. For example, some may be steep whilst others are shallow. The curvature across the cornea may not be even.

How your contact lens measurements are carried out is very simple. The process is done using a handheld instrument called a keratometer and is completely painless. This device takes a range of measurements of various aspects of your eye to determine the exact curvature. This will help your eye doctor make a recommendation as to the best contact lens style for you.

Specialty contact lenses

Sometimes lens measurements reveal that a patient has corneal abnormalities that mean that standard contact lens designs are unsuitable. For example, a diagnosis of keratoconus – which is a condition characterized by the progressive thinning and subsequent bulging of the cornea – usually means that standard contact lenses won’t fit since they won’t accommodate the bulge. Fortunately, there is a range of specialty contact lenses that are designed specifically for patients with hard-to-fit corneas. Your eye doctor will be able to advise you if this is the case for you and what lenses you should consider.

Contact lens fitting

Once all of the necessary measurements have been taken and your eye doctor has been able to recommend the most appropriate lenses to suit your needs, you will be given a trial pair of the same ones so that their fit can be checked. Whilst these won’t have the correct prescription, and so your vision will be blurred, your eye doctor will be able to check that the actual lens design works well with the shape of your cornea and sits both flushes to the eye and stable upon it. An instrument called a biomicroscope may be used to see a magnified view of the cornea to assess the success of the fit. You may also be asked to take the lenses in and out to ensure your confidence in doing so.

Once your eye doctor is happy, your prescription contact lenses will be ordered. After these lenses have been created, which usually takes around a week, you will be invited in again for a further fitting which again assesses how well the lenses sit on the eye, but also the quality of the vision that they provide.

Contact lens measurements and fitting are an essential part of any eye exam where contact lenses are being prescribed. If you have any further queries about what to expect or to schedule an appointment, please contact our expert eye care team today.



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