Glossary

accommodation
The ability of the eye's natural lens to change shape so it can focus on objects at various distances.
accommodative lens
Also known as a variable focus lens, this intraocular lens (IOL) might move in response to your eye's own muscles to adjust for near, immediate and far vision. This lens actually has a fixed focal point, but it might physically shift inside the eye in response to your vision needs.
age-related macular degeneration (AMD)
The leading cause of vision loss and legal blindness in adults over age 60, AMD affects the sharp, straight-forward vision necessary for reading, driving and other daily activities. It is an eye disease that impacts the macula, the centermost part of the retina responsible for seeing fine detail, and occurs in two forms - dry AMD and wet AMD, with wet AMD being the more serious form.
aspheric lens
An intraocular lens (IOL) that is designed to correct spherical aberrations (a change in curvature between the center and edge of your pupil that causes multiple focal points and blurry vision). This slightly flatter IOL improves contrast and makes it easier to see in varying lighting conditions.
astigmatism
A common refractive condition caused by either an irregularity in the curvature of the cornea (corneal astigmatism) or the lens (lenticular astigmatism). People with astigmatism generally have difficulty seeing fine detail at all distances. This vision disorder is treated with corrective lenses or refractive surgery.
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blue light
Blue light has a wavelength of about 475 nanometers (nm) on the visible light spectrum. Some laboratory research suggests that high-energy blue light may lead to retinal damage and play a role in the onset of age-related macular degeneration.
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capsular bag
A thin membrane that holds the eye's natural lens.
cataract
A clouding of the eye's lens that blocks passage of light to the retina, resulting in impaired vision. Often a result of normal aging, cataracts form when protein clumps cloud areas of the eye's lens. As the cataract progresses, vision worsens and often requires surgical replacement of the damaged lens with an artificial one.
choroid
The underlying layer of blood vessels in the eye that nourish the retina.
ciliary body
Circumferential tissue inside the eye composed of the ciliary muscle (involved in lens accommodation and control of intraocular pressure) and 70 ciliary processes that produce aqueous.
cornea
The clear, curved surface at the front of the eye through which light enters the eye. Along with the sclera, provides external protection for the eye.
cortical cataract
A cortical cataract occurs when the transparency of the cortex surrounding the nucleus is compromised. Cortex means "shell." While not as common as nuclear cataracts, cortical cataracts are fairly common and caused by the natural aging process.
corticosteroids
A class of steroid hormones used to treat a variety of conditions. Chronic use may lead to the formation of posterior subcapsular cataracts.
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diabetes
A disease in which the body does not produce enough, or properly use, the hormone insulin. Most Americans who are diagnosed with diabetes have Type 2 diabetes.
diabetic retinopathy (DR)
A complication of diabetes, DR compromises vision and can lead to blindness. Tiny blood vessels in the retina are weakened and leak blood and fluid into the eye, which can progress to new, abnormal blood vessel growth on the retinal surface, further affecting vision. Between 40 and 45 percent of American adults with diabetes have some form of diabetic retinopathy.
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edema
The swelling of (eye) tissues from excess fluid accumulation.
epithelium
The protective layer of cells covering the cornea.
extracapsular surgery
An older surgical technique typically reserved for very dense or hard cataracts and other special circumstances. It involves a larger incision, about three-eighths of an inch, so that the harder, central portion of the eye's natural lens can usually be removed in one piece.
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farsightedness
The common term for hyperopia, a refractive error resulting in inability to see objects at close range. Farsightedness is caused by either a cornea with too little curvature or an eyeball that is too short. Both structural defects cause light entering the eye to focus incorrectly on the retina, resulting in blurred close-up vision. Eyeglasses, contact lenses and refractive surgery are treatment options for correcting farsightedness.
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galactosemia
A hereditary disease involving the body's lack of ability to produce a liver enzyme required to digest galactose (a product of lactose – commonly found in dairy products). One of the disease's many symptoms is the formation of cataracts.
glaucoma
An eye disease that develops when too much pressure inside the eye damages the optic nerve due to the slow drainage of eye fluid through the eye's trabecular meshwork. Without treatment, glaucoma can cause permanent blindness within just a few years. Symptoms include halos around lights, tunnel vision and vision loss. Glaucoma is most often treated with medications designed to reduce intraocular pressure.
gyrate atrophy
An inherited disorder resulting in atrophy of the retina and choroid layers of the eye. Common symptoms include decreased peripheral vision and difficulty seeing at night.
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high myopia
A condition where greater than six diopters of correction are needed to focus light on the retina.
hyperopia
The medical term for "farsightedness," a refractive error resulting in an inability to see objects at close range. Typically caused by either a cornea with too little curvature or an eyeball that is too short, causing light entering the eye to focus improperly on the retina and resulting in blurry close-up vision. Eyeglasses, contact lenses and refractive surgery are treatment options for correcting vision impairment caused by hyperopia.
hypoglycemia
A condition that results from low blood sugar. Hypoglycemia also has been identified as a cause of congenital cataracts.
hypothyroidism
An endocrine disorder characterized by an underactive thyroid. Symptoms include the formation of cataracts.
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intracapsular surgery
A rarely used procedure where both the eye's natural lens and capsule are removed. This type of surgery could be performed if the lens becomes dislocated because of injury or disease.
intraocular inflammation
Determined as a cause of posterior subcapsular cataracts.
intraocular lens (IOL)
An artificial lens made of plastic, silicone, or acrylic, which is designed to be implanted in the eye to improve its focus and correct vision problems.
iris
The membrane in front of the eye's lens that manipulates the size of the pupil, thus regulating the amount of light entering the eye.
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keratometer
An instrument measuring reflected light from the cornea. A keratometer can be used to quantify the amount of astigmatism or to determine the orientation of corneal astigmatism.
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laser vision correction
A class of surgeries where a laser is used to reshape the cornea to correct refractive errors. Includes LASIK surgery.
LASIK surgery
An acronym for Laser In-Situ Keratomileusis. LASIK is a type of laser surgery in which the cornea is reshaped to improve vision. A device called a microkeratome is used to surgically create a thin, hinged flap of corneal tissue. The flap is folded back, the laser is directed to the corneal surface exposed beneath the flap and the flap is brought back into place.
Leber congenital amaurosis
A rare genetic eye disease resulting in total, or near total, blindness at birth.
lens
The transparent disc behind the pupil that brings light into focus on the retina.
light-filtering lens
An intraocular lens that filters potentially harmful rays, present in natural and artificial light.
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macula
The center-most portion of the retina responsible for central vision and the seeing of fine detail.
macular degeneration
A group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision. Hereditary types can occur at any age while age-related macular degeneration is the most common cause of decreased vision after age 50.
mature cataract
Also known as advanced, a cataract is considered mature when both the nucleus and the cortex have become completely opaque, and the lens is only able to transmit very little, if any, light.
monofocal lens
Also known as a standard lens, it is designed to provide clear vision at one fixed focal point, usually at a distance.
monovision
Vision correction that eliminates the need for bifocals or reading glasses by correcting one eye for distance and the other for up-close vision.
multifocal lens
A multifocal lens acts like trifocals or progressive lenses and is designed to includes corrections for near, intermediate and distance vision in the same lens.
myopia
A refractive error resulting in the inability for the eye to see distant objects. Also referred to as "nearsightedness." Occurs when the eyeball is too long or when the cornea has too much curvature, preventing the light entering the eye from focusing correctly on the retina and resulting in blurry vision at a distance. Eyeglasses, contact lenses and refractive surgery are treatment options for correcting vision impairment caused by myopia.
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nearsightedness
The common term for myopia. Nearsightedness is a refractive error resulting in the inability for the eye to see distant objects. Occurring when the eyeball is too long or when the cornea has too much curvature, preventing the light entering the eye from focusing correctly on the retina and resulting in blurry vision at a distance. Eyeglasses, contact lenses and refractive surgery are treatment options for nearsightedness.
nuclear cataract
With a nuclear cataract, the nucleus at the center of the lens becomes opaque. This is the most common type of cataract. Symptoms most commonly associated with nuclear cataracts include blurriness and faded colors.
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ophthalmologist
A physician (doctor of medicine or doctor of osteopathy) qualified to diagnose, manage and treat all eye and visual system disorders. An ophthalmologist is trained to render total eye care, including vision services, contact lenses, eye examinations, medical eye care and surgical eye care.
optical nerve
A bundle of nerve cells and fibers beginning in the retina that carries messages to the brain, resulting in visual images, or eyesight.
optometrist
Vision Care Specialist. Doctor of optometry (OD) specializing in vision problems, treating vision conditions with spectacles, contact lenses, low vision aids and vision therapy, and prescribing medications for certain eye diseases.
orbit
A bony, protective socket in the skull that holds the eyeball.
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phacoemulsification (phaco)
The medical term for "small incision cataract surgery." Phaco represents the majority of cataract surgeries performed today. After making a small incision on the side of the cornea, the surgeon inserts a tiny probe into the eye. The probe emits ultrasound waves that soften and break up the clouded lens, which is then removed by suction. An artificial lens (intraocular lens or IOL) is then permanently placed in the eye.
posterior subcapsular cataract
This type of cataract begins at the back of the lens and spreads to the periphery of the lens, affecting vision even more than other types of cataracts.
presbyopia
A condition in which the eye loses its natural ability to focus properly. Presbyopia is a natural result of aging and causes blurry, close-up vision. Reading glasses or corrective contact lenses are necessary to maintain quality close-range vision once presbyopia has been diagnosed.
pupil
The black, circular area in the center of the iris that regulates the amount of light entering the eye by constricting and dilating.
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refractive index
A measure for how much the speed of light is reduced inside a medium, such as glass.
retina
The transmitter located at the back of your eye that sends the images to your brain.
retinal detachment
A serious condition occurring when part of the retina lifts or pulls away from its natural position. If left untreated, it can result in significant vision impairment or blindness in a matter of days.
retinitis pigmentosa
A group of eye disorders that affect the retina and lead to vision loss. Affected individuals usually experience night blindness, followed by the loss of peripheral vision.
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sclera
The eye's white part. Along with the cornea, the sclera provides external protection for the eye.
sclerotic
Relating to sclerosis, the hardening of tissue.
spherical aberration
A change in curvature between the center and edge of your pupil that causes multiple focal points and blurry vision.
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toric lens
An intraocular lens designed for people with moderate to severe astigmatism, potentially reducing the need for glasses for distance vision following surgery.
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ultrasound
High frequency sound waves used during cataract surgery to break up the eye's natural lens so that it can be easily removed and replaced with an intraocular lens (IOL).
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Wagner syndrome
Also referred to as Wagner vitreoretinal degeneration syndrome.
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zonule
Ligaments in the eye that connect the capsular bag to the muscles in the ciliary body.

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