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      Amblyopia: Decreased vision without detectable anatomic damage in the eye or visual pathways.

      Astigmatism: An optical defect which can exist alone or in combination with nearsightedness or farsightedness. In this condition, the cornea is oval or football-shaped instead of round or beachball-shaped; this causes distortion of the image.

      Blepharitis: Inflammation of the eyelids, usually with redness, swelling and/or itching. Many causes (e.g., infection, allergy) exist.

      Cataracts: An opacity or clouding of the crystalline lens, which may be congenital or caused by trauma, disease or age. This may prevent a clear image from forming on the retina. Surgical removal of lens may be necessary to improve vision. The optical power of the crystalline must be replaced with an intraocular lens, contact lens or high power spectacles.

      Chalazion: An enlarged eyelid oil gland, due to inflammation. Treatments range from observation to drops, injections and/or surgery.

      Conjunctivitis: Commonly known as “pink eye”, conjunctivitis is inflammation of the clear membrane that covers white of eye and inner eyelid surfaces. Grittiness, redness, swelling and discharge may be present. There are many different causes; some are contagious.

      Cornea: The cornea is the "watch crystal" of the eye. It provides most of the optical power of the eye.

      Corneal Ulcer: A defect in the clear surface of the eye, associated with inflammation. There are many different causes (e.g., bacterial, fungal, viral, etc.).

      Diabetic Retinopathy: Changes in the back lining of the eye associated with diabetes mellitus. The early stage is background retinopathy (non-proliferative). This may advance to proliferative retinopathy, which includes the growth of abnormal new blood vessels (neovascularization) and accompanying fibrous tissue.

      Dry Eye: Corneal and conjunctival dryness due to deficient tear production, environmental dryness, and/or medication. Patients with dry eye may experience foreign body sensation, burning, blurred vision and/or redness. It is treated by lubrication regimens, environmental humidification, temporary and/or permanent blocking of tear ducts, and nutritional suppliments.

      Floaters: Particles that float in the vitreous and cast shadows on the retina; these are seen as spots, cobwebs, spiders, etc. They occur as a normal "rite of passage" or may be associated with vitreous separation, inflammation, or retinal tears.

      Glaucoma: An optic neuropathy often associated with increased eye pressure. Glaucoma is diagnosed by a thorough eye exam, visual field , and a nerve fiber layer analysis. A common cause of preventable vision loss, glaucoma may occur at any age but increases after the age of 40. It is treated by eye drops, pills, laser or surgery.

      Hyperopia (Farsightedness): When the curvature of the cornea is too flat, light rays entering the eye focus behind the retina. The result is a blurred image, especially of near objects.

      Iris: The pigmented tissue inside the eye that gives color to the eye (e.g., "blue eyes", "brown eyes", etc.). The iris controls the amount of light entering the eye by varying the size of the pupillary opening.

      Iritis: Inflammation of the iris. Symptoms of iritis may include pain, tearing, blurred vision, small pupil (miosis) and a red congested eye.

      Laser in Situ Keratomileusis (LASIK): A procedure to correct farsightedness, nearsightedness and astigmatism. With the LASIK procedure, a thin layer of the cornea is lifted to create a “flap” that stays connected on one side; the Excimer Laser then reshapes the cornea. Finally, the “flap” is returned to its original position.

      Lens: Natural crystalline lens of the eye. Transparent, biconvex intraocular tissue that helps bring rays of light to focus on the retina. Suspended by fine ligaments (zonules) attached between ciliary processes.

      Macular Degeneration: A group of conditions that include deterioration of the central retina (macula) resulting in a loss of sharp central vision. "Dry" Macular Degeneration involves a disturbance of pigmentation and deposits of yellowish material under the pigment epithelial layer. "Wet" Macular Degeneration is associated with abnormal new blood vessels growing under the retina. These vessels leak fluid and blood, further disturbing retinal function. Macular Degeneration is the most common cause of decreased vision after age 60.

      Migraines: A neurologic syndrome with a secondary vascular component. Migraines are due to a disorder (probably genetic) of neurologic processing of sensory information from the head or neck. The headache is often one-sided and if accompanied by jagged lights, "heat waves" or circles of light, it is called "Migraine with Aura" or "Classic Migraine". Vision changes alone without the headache are called "Ophthalmic Migraines".

      Myopia (Nearsightedness): When the curvature of the cornea is too steep, light rays entering the eye focus in front of the retina. The result is a blurred view of distant objects.

      Ocular Hypertension: Eye pressure elevated above 21 mm of mercury, with no obvious optic nerve damage or visual field defects. Glaucoma may or may not develop with time.

      Ophthalmic Graves Disease: A multisystem disease of unknown cause having one or more of three clinical entities: hyperthyroidism, skin changes, or eye signs. The eye signs may include eyelid retraction, eyelid lag on downward gaze, bulging eyes, corneal drying, and optic nerve damage.

      Ophthalmologist: Physician (M.D.) specializing in diagnosis and treatment of refractive, medical and surgical problems related to eye diseases and disorders.

      Optic Neuritis: Inflammation of the optic nerve. May accompany demyelinating disease (e.g., multiple sclerosis) or infections from the brain, orbits or sinuses. Characterized by rapid onset of decreased vision and, usually, discomfort with eye movement and a central visual field defect.

      Optometrist: Doctor of Optometry (O.D.) specializing in vision problems, treating vision conditions with spectacles, contact lenses, low vision aids and vision therapy, and prescribing medications for certain eye diseases.

      Posterior Vitreous Detachment (PVD): Separation of vitreous gel from the retinal surface. Frequently occurs with aging as the vitreous liquifies or in some diseases states (e.g., diabetes and high myopia). Usually innocuous, but can cause retinal tears, which may lead to retinal detachment.

      Photorefractive Keratectomy (PRK): A laser surgery to correct farsightedness, nearsightedness and astigmatism. An excimer laser beam is used to reshape the front of the cornea. The laser beam removes small amounts of tissue from the front of the cornea.

      Retina: Part of the eye (embryologically part of brain) that converts images from the eye’s optical system into electrical impulses that are sent along the optic nerve for transmission to the brain. The retina forms the thin membranous lining of the rear two-thirds of the globe. Consists of layers that include rods and cones; bipolar, amacrine, ganglion, horizontal and Muller cells; and all interconnecting nerve fibers.

      Retinal Detachment: Separation of sensory retina from the underlying pigment epithelium. This disrupts visual cell structure and thus markedly disturbs vision. Almost always caused by a retinal tear; often requires immediate surgical repair.

      Uveitis: Inflammation of any of the structures of the uvea (iris, ciliary body, or choroid).