Below is a glossary of terms related to eye disease and common refractive errors.
An eye disease that gradually destroys the macula, the part of the eye that provides sharp, central vision needed for seeing objects clearly.
Amblyopia is the medical term used when the vision of one eye is reduced because it fails to work properly with the brain. The eye itself looks normal, but for various reasons the brain favors the other eye. This condition is also sometimes called lazy eye.
Anophthalmia and Microphthalmia
Anophthalmia and microphthalmia are often used interchangeably. Microphthalmia is a disorder in which one or both eyes are abnormally small, while anophthalmia is the absence of one or both eyes.
Astigmatism is a common type of refractive error where the eye does not focus light evenly onto the retina. The cornea of a normal eye is curved like a basketball, with the same degree of roundness in all areas. An eye with astigmatism has a cornea that is curved more like a football, with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out.
Behçet’s Disease of the Eye
Behçet’s disease is an autoimmune disease that results from damage to blood vessels throughout the body, particularly veins. The four most common symptoms are mouth sores, genital sores, inflammation inside of the eye, and skin problems. Inflammation inside of the eye (uveitis, retinitis, and iritis) occurs in more that half of those with Behçet’s disease and can cause blurred vision, pain, and redness. This disease is also known as adamantiades.
Bietti’s Crystalline Dystrophy
Bietti’s crystalline dystrophy (BCD) is an inherited eye disease which tends to lead to progressive night blindness and visual field constriction. This disease is also known as Bietti’s crystalline corneoretinal dystrophy.
Blepharospasm is associated with an abnormal function of the basal ganglion from an unknown cause. The basal ganglion is the part of the brain responsible for controlling the muscles. Blepharospasm causes abnormal, involuntary blinking or spasm of the eyelids.
A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. A cataract can occur in either or both eyes. It cannot spread from one eye to the other.
This term describes a group of diseases that cause swelling, itching, burning, and redness of the conjunctiva, the protective membrane that lines the eyelids and covers exposed areas of the sclera, or white of the eye.
Diabetic retinopathy is the most common diabetic eye disease and is caused by changes in the blood vessels of the retina. In some people with diabetic retinopathy, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow on the surface of the retina.
Floaters are little “cobwebs” or specks that float about in your field of vision. They are small, dark, shadowy shapes that can look like spots, thread-like strands, or squiggly lines. They move as your eyes move and seem to dart away when you try to look at them directly. They do not follow your eye movements precisely, and usually drift when your eyes stop moving.
Fuchs’ dystrophy is a slowly progressing disease that usually affects both eyes and occurs when endothelial cells gradually deteriorate without any apparent reason. As more endothelial cells are lost over the years, the endothelium becomes less efficient at pumping water out of the stroma. This causes the cornea to swell and distort vision. Eventually, the epithelium also takes on water, resulting in pain and severe visual impairment.
Histoplasmosis is a disease caused when airborne spores of the fungus Histoplasma capsulatum are inhaled into the lungs, the primary infection site. Histoplasmosis can later cause a serious eye disease called ocular histoplasmosis syndrome (OHS).
Iridocorneal Endothelial Syndrome
Iridocorneal endothelial syndrome is actually a grouping of three closely linked conditions: iris nevus (or Cogan-Reese) syndrome; Chandler’s syndrome; and essential (progressive) iris atrophy. The most common feature of this group of diseases is the movement of endothelial cells off the cornea onto the iris. This loss of cells from the cornea often leads to corneal swelling, distortion of the iris, and variable degrees of distortion of the pupil, the adjustable opening at the center of the iris that allows varying amounts of light to enter the eye. This cell movement also plugs the fluid outflow channels of the eye, causing glaucoma.
Keratoconus is a disorder which causes a progressive thinning of the cornea. Keratoconus arises when the middle of the cornea thins and gradually bulges outward, forming a rounded cone shape. This abnormal curvature changes the cornea’s refractive power, producing moderate to severe distortion (astigmatism) and blurriness (nearsightedness) of vision.
Lattice dystrophy gets its name from an accumulation of amyloid deposits, or abnormal protein fibers, throughout the middle and anterior stroma. Over time, the lattice lines will grow opaque and involve more of the stroma. They will also gradually converge, giving the cornea a cloudiness that may also reduce vision.
Map-Dot-Fingerprint dystrophy occurs when the epithelium’s basement membrane develops abnormally. When the basement membrane develops abnormally, the epithelial cells cannot properly adhere to it. This causes recurrent epithelial erosions, in which the epithelium’s outermost layer rises slightly, exposing a small gap between the outermost layer and the rest of the cornea.
Presbyopia is a common type of vision disorder that occurs as you age. It is often referred to as the aging eye condition. Presbyopia results in the inability to focus up close, a problem associated with refraction in the eye.
The retina is the light-sensitive layer of tissue that lines the inside of the eye and sends visual messages through the optic nerve to the brain. When the retina detaches, it is lifted or pulled from its normal position.
Retinopathy of prematurity (ROP)
Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2¾ pounds or less that are born before 31 weeks of gestation.
Stevens-Johnson Syndrome (SJS), also called erythema multiforme major, is a disorder of the skin that can also affect the eyes. SJS can cause serious eye problems, such as severe conjunctivitis; iritis, an inflammation inside the eye; corneal blisters and erosions; and corneal holes.
Usher syndrome is the most common condition that affects both hearing and vision. One major symptom of Usher syndrome is an eye disorder called retinitis pigmentosa, or RP. Retinitis pigmentosa causes night-blindness and a loss of peripheral vision through the progressive degeneration of the retina.
Vitreous detachment is a common condition where the vitreous slowly shrinks, and these fine fibers pull on the retinal surface. Usually the fibers break, allowing the vitreous to separate and shrink from the retina. Vitreous is a gel-like substance that helps the eye maintain a round shape. There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina, the eye’s light-sensitive tissue.