Definition of Phacoemulsification

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Definition of Phacoemulsification

Phacoemulsification: A procedure in which the lens clouded by a cataract is broken upby ultrasound, irrigated, and suctioned out. Most cataract surgery today is performedusing phacoemulsification. Before the advent of this technique, people with cataracts

could expect a 10-day hospital stay followed by a lengthy recovery. Today, it is anoutpatient procedure. Instead of making a large incision in the eye and removing the lens,the ophthalmologist can make a tiny one and then insert an ultrasonic tip which, vibratingthousands of times a second, breaks up the cataracts without damaging the surroundingtissue. The remains of the cataract are suctioned out.

Phacoemulsification was introduced in 1967 by Charles D. Kelman, an Americanophthalmologist (1930-2004). In his memoir, "Through My Eyes: The Story of a SurgeonWho Dared to Take On the Medical World" (Crown, 1985), Dr. Kelman described howhe went to a dentist have his teeth cleaned. "I sat in his chair, as he reached over, took along silver instrument out of its cradle and turned it on," Dr. Kelman wrote. "A fine mist

came off the tip but the tip didn't seem to be moving. He applied the tip to my teeth, and Ifelt an exquisite vibration and heard a high-pitched sound." Dr. Kelman asked, "What isthat thing?" An ultrasonic probe, came the reply. "I knew this was the moment," Dr.Kelman wrote.

The word "phakos" in Greek is a "lentil" (a lentil bean). The prefix "phaco-" thereforerefers to the lens which is lentil-shaped.

What is a cataract?

Cataracts are clouding of the lens portion of the eye. The result is much like smearing

grease over the lens of a camera and impairs normal vision.
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Cataracts will affect most people if they live long enough. This disorder affects 60percent of people older than 60 and occurs when the normally clear, aspirin-sized lens ofthe eye starts to become cloudy. impairing vision.

Experts estimate that over 1.2 million Americans are diagnosed annually with cataractsthat require treatment. As their is are growing numbers of elderly in the United States, the

incidence of cataracts is increasing. These persons often want to continue driving cars,reading and traveling-activities for which clear sight is vital.

Until recently, anyone who developed cataracts and needed surgery faced a procedurethat involved pain and often less than satisfactory results. Until the late 1970s, doctorsremoved the cloudy lens in a surgical procedure that required a hospital stay of five toseven days. Afterward, the patient had to wear thick "Coke bottle" glasses or contactlenses neither of which could completely restore vision to its previous level.

Today, there's little need for such complicated treatment. Advances in medicine havemade cataracts much less worrisome. Now, the clouded lens is surgically removed and

replaced with a plastic intraocular lens (IOL) in an hourlong operation that often requiresno hospitalization.

"The intraocular lens has revolutionized the treatment of cataracts." says Carl Kupfer.M.D., director of the National Eye Institute in Bethesda, Md. "Implantation of the lens isone of the most successful operations in medicine."


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How does a cataract form?

A cataract forms in the eye's lens. the transparent structure behind the iris (the coloredmembrane surrounding the pupil). The lens focuses light on the retina, the light-sensitivemembrane at the back of the eye which converts light impulses into nerve signals to

produce clear visual images. Clouding of the lens, much like smearing grease over thelens of a camera, can develop at any age but most often appears in people older than 42.

Most cataracts are caused by a change in the chemical composition of the lens. In a smallpercentage of cases, the chemical changes are caused by a hereditary enzyme defect,trauma to the eye., diabetes, or use of certain drugs, such as the steroid prednisone.

Precisely why cataracts occur with age is unknown, but ultraviolet radiation, particularlyfrom the sun, is thought to play a major role in creating, the chemical change in the lensresponsible for most cataracts. Experimental evidence suggests that UV radiation cancloud the lens by forming highly reactive chemical fragments called "free radicals."

These, in turn. disrupt the delicate structure of the lens. The type of ultraviolet radiationfrom the sun called UVB-the kind that causes blistering sunburn and skin cancer-isthought to be a major factor because the lens absorbs these rays.

Indeed, in a study of 838 Chesapeake Bay professional fishermen, Hugh Taylor, M.D., ofJohns Hopkins Hospital in Baltimore, Md., found a strong association between ultravioletradiation and cataract formation. Fishermen with the highest levels of ultraviolet radiationexposure had three times the risk of contracting cataracts compared with those with theleast exposure. Those with cataracts had 20 percent more exposure to sunlight in everyyear of life. Taylor's studies suggest that cataracts can be prevented by avoiding sunexposure between 10 a.m. and 4 p.m., when sunlight is strongest, and by wearing a wide-

brimmed hat and sunglasses. (See "Shielding Your Eyes from the Sun" below).

A cataract can develop so slowly that a person may not even know it's there. If thecataract is on the outer edge of the lens, no change in vision may be noticeable.Cloudiness near the center of the lens, however, usually interferes with clear sight.

What are the symptoms of cataracts?

Symptoms of developing cataracts include double or blurred vision, sensitivity to lightand glare (such as bright sun or auto headlights), less vivid perception of color, andfrequent changes in eye-glass prescriptions. As the cataract grows worse, stronger glassesno longer improve sight, although holding objects nearer to the eye may help reading andclose-up work. The pupil, which normally appears black, may undergo noticeable colorchanges and appear to be yellowish or white.

How are cataracts diagnosed?

Cataracts are typically detected through a medical eye examination. The doctor can seethe abnormal lens using a hand-held viewing instrument (ophthalmoscope). The usual test
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for visual acuity, the letter eye chart, may not, however, reflect the true nature of visualloss, says the American Academy of Ophthalmology. Other tests-which measure glaresensitivity, contrast sensitivity, night vision, color vision, and side or central vision-helpnail down the diagnosis.

Because most cataracts associated with aging develop slowly, many patients may notnotice their visual loss until it has become severe. Some cataracts remain small and neverneed treatment, others grow more quickly and progressively larger. Only when a cataractseriously interferes with normal activities is it time to consider surgery, doctors say.People who depend on their eyes for work, play and other activities may want theircataracts removed earlier than those whose needs are less demanding.

What are the treatment options?

During the diagnostic examination, an ophthalmologist will carefully measure the shape,size and general health of the eye to determine whether a lens implant will be effective.

In the relatively small number of cases where it won't be, eye-glasses or contact lenseswill improve vision after traditional cataract surgery. Glasses, while used for years, havedrawbacks. Their extreme thickness makes them unattractive and heavy. Magnificationand distortion of the visual image causes objects to appear closer and 25 percent largerthan they are. Peripheral vision may be reduced. Contact lenses provide fairly goodvision, but many elderly people have trouble inserting, removing and cleaning them.

An implanted IOL is usually the best replacement. Because the implant is placed in ornear the original position of the removed natural lens, vision is restored with goodperipheral vision and depth perception yet with minimal magnification and distortion.

Some experts estimate that about 88 of every 100 persons receiving IOLs will achieve20/40 vision or better. (An individual with 20/40 vision can read letters on an eye chartfrom 20 feet away, while a person with normal 20/20 vision can read the chart from 40feet away; 20/40 vision is good enough to get a driver's license in most states.) Amongthose who do not have other eye diseases, about 94 of 100 will achieve 20/40 vision.

IOLs remain permanently in place, require no maintenance or handling, and are neitherfelt by the patient nor noticed by others. Eyeglasses with thin lenses for near or distantviewing may still be required, but thick glasses are not necessary. A doctor can determinethe appropriate implant prescription with an ultrasound device that measures eye lengthand corneal curvature. These measurements are combined by computer to calculate thelens power required.

What is the procedure for implantation of an IOL?

The standard surgical procedure, which ranges in cost from $3,000 to $5,000, isperformed in a hospital or doctor's office. Peering through an operating microscope, thesurgeon makes a minute, curved incision in the cornea-the surface of the eye. Then the


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clouded lens is cut loose with a thin needle and suctioned out, leaving intact the rear wallof the transparent capsule that encloses the lens.

There are three types of surgery to remove lenses that have a cataract:

1. Extracapsular surgery. The eye surgeon removes the lens, leaving behind the backhalf of the capsule (the outer covering of the lens).2. Phacoemulsification (pronounced FAY-co-ee-mul-sih-fih-CAY-shun). In this

type of extracapsular surgery, the surgeon softens the lens with sound waves andremoves it through a needle. The back half of the lens capsule is left behind.

3. Intracapsular surgery. The surgeon removes the entire lens, including the capsule.This method is rarely used.

The surgeon enlarges the original incision, and the new lens-a clear hard plastic disc-isthen slipped in behind the iris and up against the back wall of the capsule. Two tiny "c"shaped arms attached to the lens eventually become scarred into the side of the eye and

hold the lens firmly in place. The incision is closed with 7 to 10 nearly invisible stitchesof fine nylon or silk.

In a newer method, an ultrasonic probe enters the cut in the cornea and high-speedvibrations break the lens into microscopic flecks that are then removed by suction. Afolded flexible plastic lens one-quarter of an inch in diameter can be inserted through thecut with a scissors-like device called an injector and positioned behind the pupil againstthe capsule wall. Once in place, the injector is removed and the lens opens.

Some manufacturers are also developing bifocal IOLS, which may eliminate the need insome patients for prescription glasses after surgery.

The procedure to remove the natural lens and replace it with a synthetic one is done undera general or local anesthesia with injections made in muscles around the eye. Recoverytakes several hours in the hospital; in a few cases, it may require an overnight stay. Thepatient wears a metal shield over the eye at night; wrap-around sunglasses arerecommended during the day.

What happens after the IOL procedure?

Within a few days of the operation, most people are back at work. In several office visitsduring the first six to eight weeks after surgery, the doctor will check for infections or

other complications and fit the patient for reading glasses. Vision is significantlyimproved in 95 to 98 percent of cases.

However, results of the operation aren't always worry free. After the IOL implantation, aclouding of the lens capsule, known as a "secondary cataract," occurs in roughly 40percent of cases. To restore vision, a pulsed yttrium, aluminum, garnet (YAG) laser isused to produce a hole non-thermally, by "optical breakdown." in the capsule to allow thenormal passage of light rays back to the retina. This painless procedure takes a few


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minutes; improvement usually is immediate. Other problems that may occur in a smallpercentage of patients include swelling of the cornea, glaucoma, and swelling of theretina, which distorts vision.

At a time when more older Americans than ever before are looking forward to years of

active life ahead of them, IOLs clearly offer hope and a better life.

Why should I shield my eyes from the sun?...Prevention

Headed for the ski slopes or beach? These pleasures can pose dangers to your eyes unlessyou take precautions against the sun's harmful rays.

Ultraviolet radiation is invisible and cannot be felt, yet long-term exposure to it may beassociated with development of cataracts. Short-term exposure to very intense ultravioletlight- such as you get on a ski slope-can produce photokeratitis, also called actinickeratopathy or snow blindness. There is even some evidence ultraviolet radiation may

damage the eye's retina.

By spring of 1990, a new voluntary labeling program developed by the SunglassAssociation of America in cooperation with the Food and Drug Administration isexpected to be in place to tell consumers how much UV protection they can expect fromnonprescription sunglasses. (Prescription sunglasses already meet standards of protectionagainst UV radiation and are not included in this labeling program.)

The voluntary labeling program calls for manufacturers to attach a tag to sunglasses thatspecifies the level of protection from the two types of ultraviolet rays: the longerwavelength ultraviolet A (UVA) radiation and the shorter wavelength ultraviolet B

(UVB) rays. The standards were developed in 1986 by the American National StandardsInstitute in New York City through consultation with eye-care professionals andeducators, research scientists, industry, and military and other government agencies. Thelabeling standards are the only recognized statement on the properties and performance ofsunglasses.

The different categories describe minimum levels of protection and are designed to helpconsumers pick the best glasses for the types of activities they plan:

Cosmetic: For non-harsh sunlight and around-town uses such as shopping. These

will block at least 70 percent of UVB, 20 percent of UVA, and less than 60

percent of visible light. General Purpose: For most outdoor activities such as boating, flying, hiking,

picnicking, and beach outings. They also can be used for snow settings. They willblock at least 95 percent of UVB, at least 60 percent of UVA, and from 60 to 92percent of visible light.

Special Purpose: For very bright environments such as tropical beaches and ski

slopes and for activities like mountain climbing. They will block at least 99


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percent of UVB and 60 percent of UVA, in addition to from 20 to 97 percent ofvisible light.

The amount of visible light-glare blocked by sunglasses depends on the darkness of thelenses. The darker shades of special- purpose sunglasses are intended for a high level of

brightness, while the lighter shades can be used for less bright situations-like skiing on acloudy day.

In addition, within the categories, look for the actual percentage of the sun's UV radiationthat each particular model of glasses claims to block. The greater the blockage, the lowerthe risk of UV damage to the eye.

Thomas Loomis, technical director of the Sunglass Association of America, offers thisadvice when buying non- prescription sunglasses:

First, decide on the purpose, color and fashion you want. Once you've made a selection,

hold the sunglasses up at arm's length and look through them at an object with a straightborder, such as a window or door frame. Move the glasses slowly across the line. If itseems to wiggle, sway or curve, the lenses contain an optical defect and should bereplaced with another pair.

Since 8 percent of males and 3 percent of females have a vision color defect, be sure theglasses don't distort the colors of a traffic signal. Pay for the glasses, says Loomis, walkoutside the store and conduct your own test. If they distort the colors, exchange them foranother pair.

Cataracts At A Glance

Cataracts will affect most people if they live long enough. Symptoms of cataracts include double or blurred vision and sensitivity to light

and glare. Cataracts can be diagnosed when the doctor examines the eyes with a viewing

instrument. The ideal treatment for cataracts is surgical implantation of a new lens.

Sunglasses can help to prevent cataracts.

This article is in part based in information from the U.S. Food and Drug Administration(FDA).

Abnormal: Not normal. Deviating from the usual structure, position, condition, orbehavior. In referring to a growth, abnormal may mean that it is cancerous orpremalignant (likely to become cancer ).See the entire definition of Abnormal

Actinic: Referring to the ultraviolet (UV) rays from sunlight and UV lamps. Sunburn isan actinic burn. An actinic keratosis is a skinlesion that is the consequence ofchronicsun exposure. From the Greek "aktis" meaning "ray."
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Aging: The process of becoming older, a process that is genetically determined andenvironmentally modulated.See the entire definition of Aging

Aluminum: A naturally occurring element that makes up about 8% of the surface of the

earth and is always found combined with other elements such as oxygen, silicon, andfluorine. Aluminum is is the most common metallic element in the earth's crust but hasno clear biologic role. Everyone is exposed to low levels of aluminum from food, air, andwater. Exposure to high levels of aluminum may result in respiratory problems(aluminosis). Inhalation of bauxite (aluminum ore) fumes may cause pulmonary fibrosis .Aluminum in the bloodstream may lead to neurological symptoms and may be fatal.See the entire definition of Aluminum

Anesthesia: Loss of feeling or awareness. A generalanesthetic puts the person tosleep.A local anesthetic causes loss of feeling in a part of the body such as a tooth or an area ofskin without affecting consciousness. Regional anesthesia numbs a larger part of the body

such as a leg or arm, also without affecting consciousness. The term "conductionanesthesia" encompasses both local and regional anesthetic techniques. Many surgicalprocedures can be done with conduction anesthesia without significantpain. In manysituations, such as a C-section, conduction anesthesia is safer and therefore preferable togeneral anesthesia. However, there are also many types of surgery in which generalanesthesia is clearly appropriate.

Arms: An appendage in anatomyand in clinical trials. See: Arm.

Blindness: Loss of useful sight. Blindness can be temporary or permanent. Damage toany portion of the eye, the optic nerve, or the area of the brain responsible for vision can

lead to blindness. There are numerous (actually, innumerable) causes of blindness. Thecurrent politically correct terms for blindness include visually handicapped and visuallychallenged.See the entire definition of Blindness

Blurred vision: Lack of sharpness of vision with, as a result, the inability to see finedetail. Blurred vision can occur when a person who wears corrective lens is without them.Blurred vision can also be an important clue to eye disease.

Capsule: Capsule has many meanings in medicine including the following:

1. In medicine, a membranous structure that envelops an organ, a joint, tumor, orany other part of the body. It is usually made up of dense collagen-containingconnective tissue.

2. In pharmacy, a solid dosage form in which the drug is enclosed in a hard or softsoluble container, usually of a form of gelatin.

3. In microbiology, a coat around a microbe, such as a bacterium or fungus.
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See the entire definition of Capsule

Cataract: A clouding of the lens of the eye. The normally clear aspirin-sized lens of theeye starts to become cloudy. The result is much like smearing grease over the lens of a

camera. It impairs normal vision.

See the entire definition of Cataract

Cataract surgery: Removal of the clouded lens (the cataract ) in its entirety by surgery,usually followed by replacement of the lens with an intraocular lens (IOL) made ofplastic, silicone, acrylic or other material. The operation typically takes about an hour, isdone under local anesthetic only, and does not require hospitalization.

See the entire definition of Cataract surgery

Contrast: Short for "contrast media." Contrast media are X-ray dyes used to providecontrast, for example, between blood vessels and other tissue.

Cornea: The clear front window of the eye that transmits and focuses light into the eye.See the entire definition of Cornea

Corneal: Pertaining to the cornea, the clear front window of the eye that transmits andfocuses light into the eye.

Cut: An area of severed skin. Wash a cut or scrape it with soap and water, and keep itclean and dry. Putting alcohol, hydrogen peroxide, or iodine into a wound can delayhealing, and should be avoided. Seek medical care if you think you might need stitches,as delay can increase the rate of wound infection. If the cut results from a puncturewound through the shoe, there is a high risk of infection, and you should see yourhealthcare professional. Redness, swelling, increased pain, and pus draining from thewound also indicate an infection that requires professional care.

Diabetes: Refers to diabetes mellitus or, less often, to diabetes insipidus . Diabetes

mellitus and diabetes insipidus share the name "diabetes" because they are bothconditions characterized by excessive urination (polyuria).See the entire definition of Diabetes

Diagnosis:1 The nature of a disease ; the identification of an illness. 2 A conclusion ordecision reached by diagnosis. The diagnosis is rabies . 3 The identification of anyproblem. The diagnosis was a plugged IV.See the entire definition of Diagnosis
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Enzyme: A protein (or protein-based molecule) that speeds up a chemical reaction in aliving organism. An enzyme acts as catalyst for specific chemical reactions , converting aspecific set of reactants (called substrates) into specific products. Without enzymes, lifeas we know it would not exist.See the entire definition of Enzyme

Enzyme defect: A disorder resulting from a deficiency (or functional abnormality) of anenzyme. In 1902 Archibald Garrod first attributed a disease to an enzyme defect: aninborn error of metabolism. Today, newborns are routinely screened for certain enzymedefects such as PKU (phenylketonuria) and galactosemia, an error in the handling(metabolism) of the sugar galactose.

Eye: The organ of sight. The eye has a number of components. These componentsinclude but are not limited to the cornea, iris, pupil, lens, retina, macula, optic nerve,choroid and vitreous.See the entire definition of Eye

FDA: The Food and Drug Administration, an agency within the U.S. Public HealthService, which is a part of the Department of Health and Human Services.See the entire definition of FDA

Feet: The plural of foot, both an anatomic structure and a unit of measure.See the entire definition of Feet

Food and Drug Administration: The FDA, an agency within the U.S. Public HealthService, which is a part of the Department of Health and Human Services.See the entire definition of Food and Drug Administration

Glaucoma : A common eye condition in which the fluid pressure inside the eyes risesbecause of slowed fluid drainage from the eye. If untreated, it may damage the opticnerve and other parts of the eye, causing the loss of vision or even blindness.See the entire definition of Glaucoma

Health: As officially defined by the World Health Organization, a state of completephysical, mental, and social well-being, not merely the absence of disease or infirmity.

Hospital: It may seem unnecessary to define a "hospital" since everyone knows thenature of a hospital. A hospital began as a charitable institution for the needy, aged,

infirm, or young.See the entire definition of Hospital

Implant:1. To embed; to set in firmly. In embryology, the fertilized eggimplants in theuterine lining6 or 7 days after conception (fertilization). In medicine today, many thingsmay be implanted.2. That which is embedded. For example: lens implants, breast implants, cochlearimplants,defibrillatorimplants,pacemakerimplants, etc.
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Implantation: The act of setting in firmly.See the entire definition of Implantation

Incidence: The frequency with which something, such as a disease, appears in aparticular population or area. In disease epidemiology, the incidence is the number of

newly diagnosed cases during a specific time period. The incidence is distinct from theprevalence which refers to the number of cases alive on a certain date.See the entire definition of Incidence

Incision: A cut. When making an incision, a surgeon is making a cut.

Intraocular: In the eye. The intraocular pressure is the pressure within the eye.

Intraocular lens: An artificial lens made of plastic, silicone, acrylic or other materialthat is implanted inside the eye during cataract surgery. Abbreviated IOL.See the entire definition of Intraocular lens

Iris: The iris is the circular, colored curtain of the eye. Its opening forms the pupil. Theiris helps regulate the amount of light that enters the eye.See the entire definition of Iris

Laser: A powerful beam of light that can produce intense heat when focused at closerange. Lasers are used in medicine in microsurgery, cauterization, for diagnosticpurposes, etc. For example, lasers are employed in microsurgery to cut tissue and removetissue.See the entire definition of Laser

Lens: The transparent structure inside the eye that focuses light rays onto the retina (thenerve layer that lines the back of the eye, senses light and creates impulses that gothrough the optic nerve to the brain). The lens was named after the lentil bean because itresembled it in shape and size.See the entire definition of Lens

Membrane: A very thin layer of tissue that covers a surface.

Microscope: An optical instrument that augments the power of the eye to see smallobjects. The name microscope was coined by Johannes Faber (1574-1629) who in 1628borrowed from the Greek to combined micro-, small with skopein, to view. Although the

first microscopes were simple microscopes, most (if not all) optical microscopes todayare compound microscopes.

Microscopic: So small it cannot be seen without the aid of microscope. As opposed tomacroscopic (large enough to be seen with naked eye). A tiny tumor is microscopic whilea big tumor is macroscopic.See the entire definition of Microscopic
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Nail: In medicine, there are two types of nails. One is just a plain old metal nail used tohold 2 or more pieces of bone together, for example, after a fracture. The other type ofnail is the horny plate on the end of the finger or toe. Each nail anatomically has a body,lateral nail folds (on the sides), a lunula (the little moon-shaped feature at the base), and aproximal skin fold (at the base).

See the entire definition of Nail

Nerve: A bundle of fibers that uses chemical and electrical signals to transmitsensoryand motorinformation from one body part to another. See:Nervous system.

Operation: Although there are many meanings to the word "operation", in medicine itrefers to a surgical procedure.See the entire definition of Operation

Ophthalmologist: An eye doctor. A physician practicing ophthalmology. Anophthalmologist is an M.D.

Ophthalmology: The art and science of eye medicine.

Ophthalmoscope: A lighted instrument, one of the most important tools of the physician,used to examine the interior of the eye , including the lens , retina and optic nerve .See the entire definition of Ophthalmoscope

Pain: An unpleasant sensation that can range from mild, localized discomfort to agony.Pain has both physical and emotional components. The physical part of pain results fromnerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can bemore diffuse, as in disorders like fibromyalgia . Pain is mediated by specific nerve fibers

that carry the pain impulses to the brain where their conscious appreciation may bemodified by many factors.See the entire definition of Pain

Peripheral: Situated away from the center, as opposed to centrally located.See the entire definition of Peripheral

Peripheral vision: Side vision. The ability to see objects and movement outside of thedirect line of vision. Peripheral vision is the work of the rods, nerve cells located largelyoutside the macula (the center) of the retina. The rods are also responsible for night visionand low-light vision but are insensitive to color. As opposed to central vision.

Phacoemulsification: A procedure in which the lens clouded by a cataract is broken upby ultrasound, irrigated, and suctioned out. Most cataract surgery today is performedusing phacoemulsification. Before the advent of this technique, people with cataractscould expect a 10-day hospital stay followed by a lengthy recovery. Today, it is anoutpatient procedure. Instead of making a large incision in the eye and removing the lens,the ophthalmologist can make a tiny one and then insert an ultrasonic tip which, vibratingthousands of times a second, breaks up the cataracts without damaging the surrounding
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tissue. The remains of the cataract are suctioned out.See the entire definition of Phacoemulsification

Photokeratitis: A burn of the cornea (the clear front surface of the eye ) by ultraviolet Brays (UVB). Also called radiation keratitis or snowblindness.

See the entire definition of Photokeratitis

Prescription: A physician's order for the preparation and administration of a drug ordevice for a patient. A prescription has several parts. They include the superscription orheading with the symbol "R" or "Rx", which stands for the word recipe (meaning, inLatin, to take); the inscription, which contains the names and quantities of theingredients; the subscription or directions for compounding the drug; and the signaturewhich is often preceded by the sign "s" standing for signa (Latin for mark), giving thedirections to be marked on the container.

Probe: (1) In surgery, a probe is a slender flexible rod with a blunt end used to explore,

for example, an opening to see where it goes. (2) In molecular genetics, a probe is alabeled bit of DNA or RNA used to find its complementary sequence or locate aparticular clone like homing in on a needle in a haystack.See the entire definition of Probe

Pupil: The opening of the iris. The pupil may appear to open (dilate) and close (constrict)but it is really the iris that is the prime mover; the pupil is merely the absence of iris. Thepupil determines how much light is let into the eye. Both pupils are usually of equal size.If they are not, that is termed anisocoria (from "a-", not + "iso", equal + "kore", pupil =not equal pupils).See the entire definition of Pupil

Radiation:1. Rays of energy. Gamma rays and X-raysare two of the types of energywaves often used in medicine. 2. The use of energy waves to diagnose or treat disease.See also: Irradiation.

Retina: The retina is the nerve layer that lines the back of the eye, senses light, andcreates impulses that travel through the optic nerve to the brain. There is a small area,called the macula, in the retina that contains special light-sensitive cells. The maculaallows us to see fine details clearly.See the entire definition of Retina

Secondary cataract: See: Cataract, secondary.

Sensitivity:1. In psychology, the quality of being sensitive. As, for example, sensitivitytraining, training in small groups to develop a sensitive awareness and understanding ofoneself and of ones relationships with others. 2. In disease epidemiology, the ability of asystem to detect epidemics and other changes in disease occurrence. 3. In screening for adisease, the proportion of persons with the disease who are correctly identified by a
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screening test. 4. In the definition of a disease, the proportion of persons with the diseasewho are correctly identified by defined criteria.

Skin: The skin is the body's outer covering. It protects us against heat and light, injury,and infection. It regulates body temperature and stores water, fat, and vitamin D.

Weighing about 6 pounds, the skin is the body's largest organ. It is made up of two mainlayers; the outer epidermis and the inner dermis.

See the entire definition of Skin

Steroid: A general class of chemical substances that are structurally related to oneanother and share the same chemical skeleton (a tetracyclic cyclopenta[a]phenanthreneskeleton).See the entire definition of Steroid

Sunburn: Sunburn is an inflammation of the skin that develops in response to exposureto ultraviolet (UV) radiation from the sun or from tanning beds and booths that emit UVradiation . Sunburn is manifested by reddened, painful skin that may develop blisters.See the entire definition of Sunburn

Surgeon: A physician who treats disease, injury, or deformity by operative or manualmethods. A medical doctor specialized in the removal of organs, masses and tumors andin doing other procedures using a knife (scalpel). The definition of a "surgeon" has begunto blur in recent years as surgeons have begun to minimize the cutting, employ newtechnologies that are "minimally invasive," use scopes, etc.See the entire definition of Surgeon

Surgery: The word "surgery" has multiple meanings. It is the branch of medicineconcerned with diseases and conditions which require or are amenable to operativeprocedures. Surgery is the work done by a surgeon. By analogy, the work of an editorwielding his pen as a scalpel is s form of surgery. A surgery in England (and some othercountries) is a physician's or dentist's office.See the entire definition of Surgery

Trauma: Any injury , whether physically or emotionally inflicted. "Trauma" has both amedical and a psychiatric definition. Medically, "trauma" refers to a serious or criticalbodily injury, wound, or shock . This definition is often associated with trauma medicine

practiced in emergency rooms and represents a popular view of the term. In psychiatry ,"trauma" has assumed a different meaning and refers to an experience that is emotionallypainful, distressful, or shocking, which often results in lasting mental and physicaleffects.See the entire definition of Trauma

Ultrasound : High-frequency sound waves. Ultrasound waves can be bounced off oftissues using special devices. The echoes are then converted into a picture called a
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sonogram. Ultrasound imaging, referred to as ultrasonography, allows physicians andpatients to get an inside view of soft tissues and body cavities, without using invasivetechniques. Ultrasound is often used to examine a fetus during pregnancy. There is noconvincing evidence for any danger from ultrasound during pregnancy.See the entire definition of Ultrasound

Ultraviolet A: One of the three types of invisible light rays (together with ultraviolet Band ultraviolet C) given off by the sun.See the entire definition of Ultraviolet A

Ultraviolet B: One of the three types of invisible light rays (together with ultraviolet Aand ultraviolet C) given off by the sun.See the entire definition of Ultraviolet B

Ultraviolet radiation: Invisible rays that are part of the energy that comes from the sun.Ultraviolet radiation can burn the skin and cause skin cancer .

See the entire definition of Ultraviolet radiation

UV radiation: Ultraviolet radiation. Invisible rays that are part of the energy that comesfrom the sun, can burn the skin, and cause skin cancer . UV radiation is made up of threetypes of rays -- ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC).See the entire definition of UV radiation

Visual acuity: The clarity or clearness of the vision, a measure of how well a personsees. The ability to distinguish details and shapes of objects; also called central vision.See the entire definition of Visual acuity

Vital: Necessary to maintain life. Breathing is a vital function.

Voluntary: Done in accordance with the conscious will of the individual. The oppositeof involuntary.See the entire definition of Voluntary

Yttrium: A rare elemental metal. A radioactive form of yttrium is used inradiationtherapy and some types of immunotherapy.
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Documents

Definition of Phacoemulsification