Irregular astigmatism represents one of the most problematic situations a practitioner must manage. Keratoconus, an extreme case of corneal irregularity, presents a very perplexing fitting situation because of its extreme corneal asymmetry, steep corneal curvatures, and irregular astigmatism. This condition reduces a patient’s vision with increasing amounts of irregular corneal optics, corneal thinning, and corneal scarring. This is one area where GP lenses have a significant advantage over soft contacts.
In keratoconus, the cornea becomes thin and cone-shaped. Keratoconus literally means a cone-shaped cornea. This shape prevents light from focusing in the eye properly. As the disease progresses the cone becomes more pronounced, causing vision to become blurred and distorted. Because of the cornea’s irregular shape, patients with keratoconus are usually very nearsighted and have a high degree of astigmatism that is not correctable with glasses.
Despite continuing research, the cause of keratoconus remains unknown. Although keratoconus is not generally considered an inherited disorder, the chance of a blood relative having keratoconus is thought to be as high as one in 10.
Vigorous eye rubbing, although not the cause of keratoconus, can contribute to the disease process. Therefore, patients with keratoconus are advised to avoid rubbing their eyes.
In addition to nearsightedness and astigmatism, signs and symptoms include blurred vision even while wearing glasses or contact lenses and light sensitivity.
Keratoconus is usually diagnosed in patients as young as their 20′s. For some, it may advance over several decades, for others, the progression may reach a certain point and stop. Tests can provide your eye doctor with details about the cornea’s shape and is used to detect and monitor the progression of the disease.
The first line of treatment for patients is to fit rigid gas permeable (RGP) contact lenses. Because this type of contact is not flexible, it creates a smooth, evenly shaped surface to see through. When vision deteriorates to the point that contact lenses no longer provide satisfactory vision, corneal transplant may be necessary to replace the diseased cornea with a healthy one. If corneal transplant is necessary for advanced keratoconus, vision usually improves, although specialty contact lenses are needed in conjunction with the transplant for this success. As in any eye surgery, complications such as transplant rejection, infection and loss of vision can occur, so results cannot be guaranteed.