Glossary of Vision Terms

Age-Related Macular Degeneration (AMD)--An eye disease that results in a loss of central, "straight-ahead" vision. AMD is the leading cause of vision loss in older adults.¹

Amblyopia--Also known as “lazy eye,” amblyopia is reduced vision in a healthy eye. Vision must develop, and development is impaired when eyes do not focus equally or maintain proper alignment. The brain ignores the information from the less favored eye. In either case, if this condition persists, the weaker eye will not develop normally. In babies, who are learning to use their eyes as a team, it’s easier for an eye doctor to distinguish between appropriate development and delays that could signal the need for intervention. Early detection of amblyopia is important because treatments such as patching and eye drops are most effective the earlier they are started.⁵

Astigmatism--Astigmatism blurs vision at all distances because the optical parts of the eye (cornea and lens) do not focus light onto the retina clearly. This condition is quite common, and results from an unequal curve of the cornea when comparing the horizontal and vertical planes. For descriptive purposes, imagine half of a tennis ball, squeezed at the top and bottom; the ball is now curved unequally. In the eye, this results in inaccurate focus on the retina. Lenses are often used to help focus the light to eliminate blurriness from astigmatism.⁵

Cataract--A clouding of the lens. People with cataracts see through a haze. Ina usually safe and successful surgery, the cloudy lens can be replaced with a plastic lens.¹

Cornea--The clear, transparent cover over the iris and pupil on the front part of the eye. The cornea is the first part of the eye that bends (or refracts) the light and provides most of the focusing power of the eye. ²

Corneal Transplant--A surgical treatment where the patient's diseased, cloudy or distorted cornea is cut away and a clear cornea, donated by someone who has died, is sewn into its place.² A corneal transplant can correct vision problems caused by infections, injuries, or medical conditions. It is often recommended for the following: Keratoconus, a cornea scarred from infection or injury, clouding of the cornea, and Pseudophakic bullous keratopathy.–clouding and swelling of the cornea after cataract surgery (rare with modern cataract surgery techniques) ⁴

Diabetes--A chronic disease related to high blood sugar that may lead to vision loss.¹

Diabetic Retinopathy-- Changes in the retina due to diabetes. Adverse changes in the retinal blood vessels leads to weakening and eventually to more serious eye disorders. In its most advanced stages, diabetic retinopathy can lead to severe vision loss or blindness.³

Glaucoma--A group of eye diseases characterized by pressure that is too high for the optic nerve (the nerve that sends the signal of images created by the eye to the brain) to withstand. Damage to the optic nerve from glaucoma results in loss of peripheral and then central vision. Glaucoma may be treated with medications or surgery to try to stop further damage to the optic nerve and further loss of vision.²

Hyperopia--Often called farsightedness, hyperopia is when the eyeball is too short for the normal focusing power of the eye. Depending on severity, it can cause blurred near and distance vision, eye fatigue and sometimes amblyopia or crossed eyes.⁵

Keratoconus--A condition in which the cornea develops a thin cone-shaped bulge that can result in extreme blurring and distortion of vision.³ Keratoconus is often times only correctable with specialty contact lenses, and eventually a corneal transplant.

Low Vision--A visual impairment, not corrected by standard eyeglasses, contact lenses, medication, or surgery, that interferes with the ability to perform everyday activities.¹

Myopia--Often called nearsightedness, myopia causes distant objects to appear more blurred than near objects. The eyeball is too long for the normal focusing power of the eye.⁵

Ophthalmologist--A medical doctor who diagnoses and treats diseases and disorders of the eye, and can prescribe glasses and contact lenses.¹ Some ophthalmologists specialize in a specific area of the eye (i.e. retinal specialists).

Optic Nerve--The large nerve of the eye that carries visual signals from the retina to the brain to allow sight. Damage to the eye's optic nerve results in loss of vision or blindness. Once the optic nerve is permanently damaged, it cannot be repaired or replaced by a transplanted optic nerve.²

Optician--A trained professional who grinds, fits, and dispenses glasses by prescription from an optometrist or ophthalmologist.¹

Optometrist--An eye care provider who prescribes glasses and contact lenses, and diagnoses and treats certain conditions and diseases of the eye.¹

Presbyopia--The eye's inability to accommodate focus at near, middle, and far distances. The condition is thought to develop because the eye's natural lens (crystalline lens) loses its elasticity with aging, and is unable to retain appropriate flexibility to achieve focus. The condition usually develops beginning at about age 40.⁶

Pseudophakic bullous keratopathy-–Clouding and swelling of the cornea after cataract surgery (rare with modern cataract surgery techniques)⁴

Retina--A thin layer of sensory tissue that lines the inside wall of the back part of the eyeball. The retina acts like the film in a camera to capture images created by the focusing power of the cornea and the lens and transform them into electrical signals that are sent to the brain through the optic nerve.²

Retinal Detachment--Separation of the retina from its attachments to the back of the eyeball often resulting in loss of vision. Flashing lights, floating spots, and blank spots in vision can be symptoms of a retinal detachment.²

Specialist in Low Vision--An ophthalmologist or optometrist who specializes in the evaluation of low vision. This person can prescribe visual devices and teach people how to use them.¹

Strabismus--Strabismus occurs when one eye does not aim at the same object being viewed as the other eye. The “eye turn” may be present continuously or only occasionally, and the turn may be inward toward the nose (esotropia), outward (exotropia), up, or down. There is a common misconception that a child will outgrow crossed-eyes. Untreated, this condition can lead to amblyopia⁵

Vision Rehabilitation Teacher--A person who trains people with low vision to use optical and nonoptical devices, adaptive techniques, and community resources.¹

Visual and Adaptive Devices--Prescription and non-prescription devices that help people with low vision enhance their remaining vision. Some examples include magnifiers, large print books, check-writing guides, white canes, and telescopic lenses.¹

FOOTNOTES:

(1)What You Should Know About Low Vision; US Department of Health and Human Services; National Institutes of Health; National Eye Institute; NIH Publication No. 03-4672; Revised April 2003; Reprinted March 2005.

(2)http://www.fda.gov/cdrh/phakic/glossary.html

(3)http://iei.ico.edu/glossary.html

(4)http://www.med.nyu.edu/patientcare/library/article.html?ChunkIID=101016

(5)http://www.infantsee.org/x3635.xml

(6)http://vision.about.com/od/glossary/g/presbyopia.htm

ADDITIONAL RESOURCES:

Eye Bank Association of America - http://www.restoresight.org

National Eye Institute, National Institutes of Health - http://www.nei.nih.gov

The National Keratoconus Foundation - http://www.nkcf.org

InfantSEE - http://www.infantsee.org/x3635.xml