PRK Abbreviation for photorefractive keratectomy, a surgical procedure in which an excimer laser removes corneal tissue to correct vision problems such as m yop ia. The difference is that the viewing zones gradually blend into each other, for lenses that are more attractive to wear . Pupil The small dark portion in the center of the eye, the pupil opens and closes to regulate the amount of light, and thus the amount of visual information, the retina receives . Refraction A measurement of the eyes to determine the level of visual acuity. Most refractions are performed by optometrists, though many ophthalmologists do them as well.
Refractions often result in a prescription for glasses or contact len ses.
Any type of surgery, whether performed with a blade, laser, or waterjet, that corrects visual acu ity. Retina Thin tissue in the back of the eye that receives an image formed by the lens and converts it to electrical impulses carried by the optic nerve to the brain . Rewetting solution Drops that contact lens wearers can use all day if needed to keep the eye moi st. RGP lens Abbreviation for rigid gas permeable lens. Same as oxygen perme able lens.