OPTOMETRIST - Eye care professional, graduate of optometry school, provides non-surgical visual care. Specifically educated and trained to examine the eyes, and determine visual acuity as well as other vision problems and ocular abnormalities. An optometrist prescribes glasses and contact lenses to improve visual acuity. PHOTO REFRACTIVE KERATECTOMY (PRK) - Surgery in which a small area on the corneal epithelium (surface cells) is gently polished away. The laser then reshapes the corneal surface in exactly the same way as for LASIK surgery. PRESBYOPIA - Inability to maintain a clear image (focus) as objects are moved closer. Presbyopia is due to reduced elasticity of the lens with increasing age. PRP (PLATELET RICH PLASMA) - As a concentrated source of blood plasma and autologous conditioned plasma, PRP contains several different growth factors and other cytokines that can stimulate healing of soft tissue and joints. PUPIL - Black circular opening in the center of iris through which light passes into the crystalline lens. It changes size in response to the amount of light being received by the eye, i.e., larger in dim lighting conditions and smaller in brighter lighting conditions REFRACTION - Test to determine the refractive power of the eye; also, the bending of light as it passes from one medium into another REFRACTIVE ERRORS - The degree of visual distortion or limitation caused by inadequate bending of light rays, includes hyperopia, myopia, and astigmatism REFRACTIVE POWER - Ability of an object, such as the eye, to bend light as light passes through it REFRACTIVE SURGERY - Type of surgery (such as LASIK) that affects the refraction of vision 65