Emory Healthcare 
Medical terms sometimes sound like a different language. We understand. Here we’ve defined some common terms you may hear in eye care.
These are simple definitions. They aren’t a substitute for professional medical advice. If you have a question about the meaning of a term, please ask your doctor.
Condition when one eye develops significantly poorer vision than the other; also known as “lazy eye”
Fluid-filled space in the eye between the cornea and iris
Clear, watery fluid between the cornea and the vitreous; nourishes the lens and maintains eye pressure
Irregularly-shaped cornea, which causes blurred or distorted vision
Cloudy or opaque portion of the lens that can block vision Learn More
Thin layer of major blood vessels between the retina and sclera
Ring of muscle fibers that holds the lens
Smooth muscle portion of the ciliary body that controls the shape of the lens as it contracts or relaxes
Part of the ciliary body that produces the aqueous humor
Receptor cells in the retina that detect color and fine detail
Transparent mucous membrane that lines the inner surfaces of the eyelids and covers the sclera (except at the cornea)
Inflammation or infection of the conjunctiva; also known as “pink eye”
Dome-shaped window that protects the eye and helps focus light on the retina
Surgery that removes a diseased or scarred cornea and replaces it with a donor cornea Learn More
Condition associated with diabetes that causes retinal changes and can lead to bleeding in the eye
Unit that measures the optical power of an eyeglass lens or contact lens
White or yellowish deposits in the retina that commonly occur after age 60
Normal refractive state of an eye where light travels to the retina and creates clear, sharp vision; also known as “20/20 vision”
Process to replace defective genes, like those that cause retinal degenerations (such as macular degeneration)
Group of diseases caused by increased pressure in the eye that can damage the optic nerve Learn More
Refractive error of the eye that makes close vision blurry and distance vision clear
Tiny, transparent ring that changes the shape of the cornea to correct nearsightedness
Plastic implant that replaces the eye’s natural lens
Ring of muscle fibers behind the cornea that determine eye color
Hereditary, degenerative condition that causes the cornea to thin and protrude into a cone-like shape Learn More
Surgical procedure that pulls back the top layer of the cornea and shapes the middle layer to correct nearsightedness, farsightedness, and astigmatism Learn More
Almond-shaped, elastic structure within the eye that focuses images onto the retina
Surgical removal of the lens
Central portion of the retina that’s responsible for the sharpest sight
Common eye disease that can lead to blindness Learn More
Malignant (cancerous) tumor that can appear on the eyelid, orbit, choroid, and iris
Refractive error that makes near objects appear clearer and distant objects blurry
The largest nerve of the eye; connects the retina to the brain
Flattened back portion of the ciliary body
Space filled with aqueous humor between the back of the iris and front of the vitreous
Condition caused by the lens losing elasticity due to aging; makes it hard to read close-up print
Condition that causes the upper eyelid to droop
Innermost layer of blood vessels and nerves that receives visual images and transmits signals to the optic nerve
Hereditary condition where abnormal pigmentation on the retina causes progressive vision loss
Experimental therapy that transplants healthy retina cells on damaged areas of the retina
Rare type of eye cancer in children due to a malignant tumor in the retina Learn More
Condition caused by abnormal blood vessels in the retina that affects premature infants
Receptor cells in the retina that help vision in dim light
Tough outermost layer of the eye joining the cornea; the visible part is the white of the eye
Eye misalignment due to an imbalance in the muscles holding the eyeball
Series of canals or tubes behind the iris that filters the aqueous humor and allows it to drain into the bloodstream
Pigmented layers of the eye; includes the iris, ciliary body, choroid, and most of the eye’s blood vessels
Inflammation of any of the uvea’s structures Learn More
Surgical removal of the vitreous, blood, and/or membranes from the eye
Clear jelly that fills the eyeball behind the lens and transmits light to the retina
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