The first symptom noticed in keratoconus is often blurred vision. The glasses prescription will usually shift, and astigmatism will often increase resulting in blurry or distorted vision. This occurs because the shape of the cornea is slowly changing and losing its normal curvature. This usually happens in both eyes but can be worse in one eye compared to the other. Keratoconus can cause symptoms that range from mild blurry vision to severe vision loss. Typically, symptoms become noticeable in adolescence or early adulthood, usually during the teens through early 20’s. Keratoconus will commonly progress during the second and third decade of life. Over time, the progression of keratoconus will slow. Usually by the time a patient with keratoconus is in their 40’s or 50’s the progression will stop. The cornea focuses about 70% of the light coming into the eye. The lens focuses the remaining 30% of the light so that when the light reaches the retina, it is well focused and clear. Light is transformed by the retina into nerve signals which are sent to the brain through the optic nerve. The brain then interprets the data coming from the retina and allow us to see. The cornea plays a very important role in this process. If the cornea loses its perfectly curved shaped from keratoconus, then the vision will be blurry even if the lens and retina are completely normal.