What is an Astigmatism and What is Keratoconus?

By Dr. Cheryl G. Murphy, OD

It is not uncommon for patients to come in and ask their doctor what an astigmatism is or for them to become concerned when they are told they have one. However, there is little need for alarm. An astigmatism is quite common and easily correctable with glasses, contacts or refractive surgeries. Keratoconus on the other hand is something that is less common and can sometimes be tricky to manage.

An astigmatism is a common eye problem that can make one’s vision blurry or distorted. It happens when the cornea (the clear front layer of the eye) or lens (an inner part of the eye that helps the eye focus) has a different shape than normal.” Similarly, keratoconus has to do with the cornea taking on a different shape than normal, however, it is a corneal condition that is more severe, occurs a lot less frequently in the general population and patients with it tend to have a genetic predisposition, meaning usually someone in their family also has been previously diagnosed with it.

Keratoconus comes from the Latin and Greek roots kerato meaning “cornea” and conus meaning “cone.” According to the American Academy of Ophthalmology, “Keratoconus is when the cornea thins out and bulges like a cone. Changing the shape of the cornea brings light rays out of focus. As a result, vision is blurry and distorted.” The condition usually first manifests when patients are in their late teens or early twenties. In addition to blurry and distorted vision, patients can be sensitive to glare and light. During a thorough, comprehensive eye care exam, eye doctors can help to diagnose keratoconus by checking for early changes to the cornea like irregular astigmatism, Vogt’s vertical striae, Fleischer’s Ring, prominent corneal nerves, a red reflex (oil droplet sign), a scissoring reflex or by interpreting corneal topography and keratometry measurements which may reveal an abnormally steep or thinning cornea.

An astigmatism can be corrected with glasses, contacts or refractive surgeries. Similarly, keratoconus can be managed a number of different ways based on its severity. Visual blur and distortion induced by mild or early forms of keratoconus can be treated with prescription glasses or the fitting of soft contact lenses after a careful refraction and detailed measurements are taken by an optometrist. If optimal visual acuity is not achieved with glasses or soft contact lenses, optometrists can perform a more detailed contact lens fitting of hard or rigid gas permeable lenses in order to correct for corneal irregularities made by the increasing corneal curvature and thinning in more moderate forms of keratoconus. Optometrists may refer some keratoconic patients to ophthalmologists for corneal cross linkage with riboflavin and UVA which has been shown to stabilize and strengthen a changing keratoconic cornea. Intacs, penetrating keratoplasty and lamellar keratoplasty are other techniques ophthalmologists may employ to help certain patients with keratoconus.

Finding a knowledgeable and well trained eye care professional is the first step in managing keratoconus and even an astigmatism. Even though having an astigmatism is much more common, it is important to find a doctor who will take the time to do a thorough exam and refraction in order to not only write a prescription for glasses or contacts that is clear but also visually comfortable. When a patient first starts wearing a prescription that corrects for an astigmatism, it may “feel funny” or “a little strong.” However, this feeling usually subsides within a week of wearing the new glasses and they then benefit from ultra fine clarity without that “funny feeling” being there. If something still doesn’t feel quite right after a week of wearing the new glasses or contacts, patients shouldn’t just give up on them and throw them out or go back to wearing their old prescription. Instead, they should reach out to their eye doctor and see them again. Sometimes little tweaks, changes or adjustments are all it takes to make the patient not only see more clearly but also to be more comfortable and happy with their new prescription.


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