G L O S S A R Y ABERRATION - Distortions, related to astigmatism, that cause the inability of light rays entering the eye to converge (come together) to a single focus point on the retina. Aberrations are divided into two main categories: higher-order and lower-order ABLATION - Surgical removal of tissue, typically using a cool beam laser ABLATION ZONE - The area of tissue that is removed during laser surgery ACCOMMODATION - Ability of the eye to change its focus between distant objects and near objects ACUITY - Sharpness, acuteness, or keenness of vision ASTIGMATISM - Structural defects of the eye in which the light rays from a viewed object do not meet in a single focal point, resulting in blurred images being sent to the brain. An astigmatic cornea is not perfectly rounded like a basketball but has an irregular shape more like the side of a football. Astigmatism is most often combined with myopia or hyperopia. AUTOLOGOUS - a situation in which the donor and recipient are the same person BIFOCALS - Lenses containing two focal lengths, usually arranged with the focus for distance above and near focus below BLEPHAROPLASTY - a cosmetic surgical procedure that removes fat deposits, excess tissue, or muscle from the eyelids to improve the appearance of the eyes CATARACT - Gradual clouding of the crystalline lens resulting in reduced vision or eventual blindness, correctable by cataract surgery CATARACT SURGERY - Removal of a cataract, replacing it with an intraocular lens implant 60