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Ophtalmic Glossary
Aberrations: Distorted or out-of-focus images resulting from vision disorders. Low order aberrations include: Myopia, Hyperopia and Astigmatism while high order aberrations consist of decreased contrast sensitivity or night vision, glare and halos.
Age-Related Macular Degeneration (AMD): Deterioration of the Macula (an important sensory area of the retina) due to age.
Aqueous Humor: A clear fluid that flows between the cornea and the crystalline and nourishes them.
Astigmatism: A condition in which the eye has an oval shape instead of a round one. The oval shape has two curves with one flatter so that the light focuses in two points on the retina instead of one. This condition results in distorted or blurred vision.
Blind Spot: Also called optic disc is a region of the retina that has no light sensitive cells. It is located where fibers of the optic nerve emerge from the eyeball.
Cataract: Clouding of the crystalline (eye lens) which results in loss of contrast sensitivity so that contours, shadows and colors appear less vivid.
Ciliary Muscle: Tiny muscles that are attached to the crystalline (eye lens). They are responsible for reshaping the crystalline to create sharp focus.
Color Blindness: Decreased ability to differenciate between colors and specially green and red.
Cornea: The transparent convex external window of the eye that is located in front of the pupil and the iris. It transmits and focuses light into the eye.
Crystalline: Natural lens that is transparent and biconvex. It is located inside the eye and is responsible of focusing light into the retina.
Detached Retina: Detachment of the retina occurs when it is pulled away from its normal position in the back of the eye.
Diopter: Unit of measurement of the refractive power of an optical lens. Positive measure indicates hyperopia while negative numbers indicate myopia.
Dry Eye Syndrome: Feeling of burning, grittiness and sensitivity of light due to insufficient moisture in the eye.
Endothelium: Tissue that covers the internal surface of the eye within the eye cavity.
Epithelium: Tissue that covers the external surface of the eye.
Excimer Laser: Type of lasers used in eye surgery and other surgeries. Excimer lasers are cool (they do not produce any heat) and they are very finely tune (they cut tissue very precisely).
Floaters: Tiny spots or strands that float in the field of vision. They move when the eyeball moves so they can't be focused upon. They are shadow cast of small clusters of cells floating through the vitreous humor.
Glaucoma: Vision disorder caused by high intraocular pressure. The most frequent types of Glaucoma are: open angle glaucoma and closed angle Glaucoma.
Haze: Clouding of the cornea which causes feeling of seeing through smoke or fog. It is a possible complication after a PRK Excimer laser surgery. It doesn't occur with Lasik.
Hyperopia: Also known as farsightedness is one of the lower order aberration in which distant objects appear blurry.
Iris: Colored tissue that is located behind the cornea. It controls light by contracting and dilating the opening (pupil).
Intraocular Lens Implant (IOL): Permanent artificial lens that is implanted inside the eye after surgical removal of the natural lens of the eye (the crystalline) due to clouding or inability to focus normally.
Keratoconus: Is a condition in which the structure of the cornea is changed causing it to become thin and deformed. It gains a conical shape instead of the gradual curvy surface.
Lasek: Laser Assisted In-Situ Keratomilieusis is a refractive surgical procedure for correcting myopia, hyperopica and astigmatism in which excimer laser ablation is performed.
Monovision: Adjustment of one eye for near vision and of the other for distance vision so that each eye is working separately instead of working together. It can be achieved surgically, with intraocular lenses or with contact lenses.
Myopia: Also known as nearsightedness, it is a refractive error in which the eyeball is too long or the cornea has too much curvature so light entering the eye isn't focused directly on the retina but in front of it. Distance objects appear out of focus.
Peripheral vision: Ability to perceive objects, motion or colors that are not situated on the central line of vision.
Presbyopia: Presbyopia is a condition when the crystalline (the eye's lens) loses its ability to focus. Patients with Presbyopia have difficulty seeing close objects.
PRK (Photorefractive Keratectomy): Type of laser eye surgery used to correct mild to moderate refractive errors such as myopia, hyperopia and astigmatism.
Refractive Error: Is an error in refraction of the eye, an optical defect in an unaccommodating eye so that light rays do not focus on the retina which result in a distorted or blurred image.
Retina: Part of the eye located at the back of the eye, it is lined with light sensitive cells that capture the formed image and transmit it to the brain through the optic nerve.
Sclera: White outer layer of the eye that is protective and tough.
Slit-Lamp Examination: Low-power microscope with high intensity light source and used in conjunction with a biomicroscope. The lamp facilitates an examination of the anterior segment, or frontal structures and posterior segment, of the human eye.
Stroma: Middle thickest layer of the cornea.
Tonometry: Procedure that measures the intraocular pressure: a test for Glaucoma.
Tunnel Vision: Loss of peripheral vision. The patient can only see what is directly ahead of him.
Visual Field: The whole area that is visible when the eyes are looking straight ahead.
Visual Acuity: Assessment of the eye's ability to see objects clearly and precisely.
Wavefront Technology: Produces a detailed map of the eye or fingerprint of vision. This technology uncovers unique characteristic of the eye that cannot be measured by standard methods.