Ординатура / Офтальмология / Английские материалы / The Encyclopedia of Blindness and Vision Impairment_Sardegna, Shelly, Shelly, Steidl_2002

Diplopia may go unnoticed in adults or children due to poor general vision or suppression of image. Children often accommodate to the double image by suppressing the image of one eye, a condition called AMBLYOPIA. This condition may lead to vision loss.

Diplopia is a serious symptom and requires examination of the eyes. The examination involves testing of the gross eye movements to check the degree of separation of images in various positions. The Hess chart, red-glass test, or the cover-uncover test may be used.

The Hess chart test involves placing a red Þlter in front of one eye and a green Þlter in front of the other. The patient looks at a screen of small white dots. The patient is asked to point to speciÞc dots with a pointer. The amount of mislocation is measured.

The red-glass test involves placing a red glass in front of the right eye and a green glass in front of the left. The patient looks at a light 20 feet away and then at a separate light 14 inches away. The patient tells the examiner if separate red and green lights are seen while Þxating on the near or far light.

During the cover-uncover test the patient looks at a letter or object at 20 feet. One eye is covered and the other is observed to see whether it moves to Þxate on the object. If the eye moves, a disorder is present. The other eye is tested at 20 feet and then both are tested at 14 inches.

Diplopia may be caused by misalignment of the eyes, as in STRABISMUS (or a latent strabismus from childhood), an ocular muscle imbalance; third, fourth or sixth cranial nerve palsy; orbital lesions; muscle lesions; cataracts; nerve lesions; multiple sclerosis; myasthenia gravis; injury to the orbit; thyrotoxicosis, in which extraocular muscles become inßamed; stroke; or intracranial tumor.

Diplopia may often be treated with corrective lenses, surgery or medication therapy of the underlying cause.

Burde, Ronald, Peter J. Savino and Jonathan D. Trobe.

Clinical Decisions in Neuro-Ophthalmology. St. Louis: C.V. Mosby Company, 1985.

Eden, John. The Eye Book. New York: Penguin Books, 1978.

Galloway, N. R. Common Eye Diseases and their Management.

Berlin: Springer-Verlag, 1985.

Phillips, Calbert I. Basic Clinical Ophthalmology. London: Pitman Publishers Limited, 1984.

disability There is no complete consensus on terms concerning the topic of blindness and vision impairment. Rehabilitation experts, doctors, educators, and other leaders in the Þeld determine and deÞne terminology according to their own preferences and viewpoints. In recent years, those involved in the Þeld of blindness and vision impairment have made efforts to standardize terms such as disability to eliminate confusion or misinterpretation.

A disability may be deÞned as the way an impairment (a diagnosed defect or malfunctioning of a body part or organ) affects an individualÕs ability to function. It is the limitation, restriction, or disadvantage due to the malfunction.

See TERMINOLOGY.

disability insurance benefits See SOCIAL SECURITY

BENEFITS.

Disability Rights Education and Defense Fund (DREDF) A nonproÞt advocacy group founded in 1979 by leaders in the disability rights movement. It is the only advocacy organization that represents all disabled persons as a class. The goal of DREDF is to change policies and attitudes that contribute to discrimination of disabled persons and prevent them from fully participating in all aspects of life. The organization addresses laws and policies that will ensure disabled persons integration into schools, jobs, and community life.

Nationally, DREDF advises Congress and other policy makers concerning disability civil rights issues; participates in civil rights coalitions, including those representing womenÕs and disability groups; provides a national network of legislative information for disabled persons and their families; and coordinates and submits to the U.S. Supreme Court Òfriend of the courtÓ briefs on disability rights issues.

On a local level, DREDF provides legal representation to disabled persons and their families in cases of school placement, respite and child care, and discrimination by employers, landlords, and businesses.

It educates and advises the California state legislature on issues affecting the rights of disabled persons.

DREDF publications include the Disability Rights Education and Defense Fund News.

Contact:

Disability Rights Education and Defense Fund, Inc. Government Affairs OfÞce

1629 K Street NW, Suite 802 Washington, DC, 20006 202-986-0375 (ph) 202-775-7465 (fax)

DREDFÕs main ofÞce is located at:

2212 Sixth Street Berkeley, CA 94710

510-644-2555 (voice and TTY)

510-841-8645 (fax) www.dredf.org

divergence Divergence is the movement of the eyes from a convergent position. Convergence is the turning-in movement of the eyes to focus on a near object. When the object is too close to the nose to be seen as one image, the eyes diverge, or move from the convergent position.

dog guide laws All of the 50 states, plus Puerto Rico, have enacted statutes that regulate dog guides. All states guarantee the legal right of a blind person to be accompanied by a trained dog guide on all public transportation and in all public accommodations.

Public transportation is described as all modes of public conveyance and includes airplanes, trains, boats, buses, taxis, and elevators. Public accommodations are anywhere the public is invited. They include city streets, stores, restaurants, hotels, lodging places, resorts, amusement parks, educational institutes, and public buildings. The blind person cannot be charged a fee for the dog guide but is liable for any damage to the premises that the dog might cause.

Violation of the law by a person or organization generally results in a Þne or imprisonment. Some states allow dog-guide users who are denied their civil rights to take the offending parties to court.

Although the above minimum statutes apply in all 50 states and Puerto Rico, some dog-guide laws designate speciÞc restrictions while others extend rights. Some states require the dog guide to be in harness or compel the owner to muzzle the dog guide upon request. Others speciÞcally note that dog guides may not occupy a seat or that the blind person must carry and show, on request, the identiÞcation card issued by the school that trained the dog. Others allow dog guides to be exempt from licensing regulations or fees.

In Hawaii, dog guides, like all dogs entering the state, must undergo a 120-day quarantine. However, dog guide users may stay with their dogs in special cottages on quarantine grounds. Dog guides are not exempt from the regular quarantine fee.

Some state laws order drivers to use every safeguard to avoid injury or endangerment to a dogguide user traveling the streets. Drivers must yield the right of way to a crossing user and bring the car to a stop if necessary.

Many states include in the dog-guide law assurances that dog-guide users have the right to equal accommodation in commercial housing. The deÞnition for commercial housing varies greatly from state to state. It may be described as one or more of the following: a self-contained dwelling unit; property offered for rent, lease, or compensation; group homes; residential communities; or public-assisted housing. Many states make speciÞc exceptions for single-family private homes that offer one rental room only. Some stipulate that a fee cannot be charged due to the presence of the dog guide; others allow the landlord to levy a limited security deposit against possible damage incurred by the dog guide.

Some states express the right of dog-guide users to have equal employment opportunity in state employment, public schools, or any employment supported by public funds, so long as the person is qualiÞed to perform the job.

A number of Canadian provinces have enacted dog-guide laws that closely resemble the basic statutes of those in the United States. Dog-guide users must carry a current health record for the dog guide, including proof of rabies vaccination, when crossing the Canadian-American border. Users are advised to include an identiÞcation card from the

dog-guide training school and a muzzle, because in many provinces muzzling is required.

dog guides Dog guides are specially trained dogs that provide protection, independent travel and companionship to blind persons. Approximately 1 percent of the nationÕs blind persons use dog guides.

The training of dogs began in Germany during World War I. Dogs used to carry messages onto the battleÞeld were found to locate wounded soldiers and lead rescuers to their aid. As a result, the Germans began to train these dogs as guides for men blinded during the war. Dorothy Harrison Eustis, an American living in Switzerland, learned of this development and developed a training program for dog guides. Eustis returned to the United States and established the first American dog guide school, The Seeing Eye Inc., in 1929. Although modern dog guide schools vary in the services they offer, many breed and train dogs, train dog guide instructors, instruct blind persons on how to use and care for dog guides, and provide public information.

Both male and female Labradors, golden retrievers, and German shepherds are most often preferred as dog guides, although boxers, Doberman pinschers and collies are also used. New puppies are examined and tested at the school to determine physical health, intelligence, responsibility, and willingness to learn and please. Suitable puppies are sent to live with a foster family. The puppies live with the family for approximately one year in which they learn socialization and, in some cases, obedience skills. The 4-H Clubs and other volunteer puppy-raising organizations often work closely with schools to place new puppies in homes. After a year or longer, the dogs return to the dog-guide school for formal training. They are taught basic obedience skills and are introduced to the leather harness that is worn when traveling.

The dogs learn to lead rather than walk in the heel position, to stop at curbs and stairs, to avoid obstacles, both on the ground and overhead, to ignore distractions and to disobey instructions that put the user in danger. The training may last from three to six months. Roughly half of the dogs

trained to be dog guides do not pass the training requirements. They are usually offered to the foster family for adoption or placed in other good homes.

After graduation from training, the dog is matched with a blind person. The student and dog live, eat and train together at the school for four weeks. Training sessions include traveling skills, transportation use in both residential and urban settings, and grooming, rewarding, and disciplining the dog guide.

The blind student learns to direct the dog and to understand the signals felt through the U-shaped handle of the leather harness. Dogs are color blind and therefore cannot distinguish a red trafÞc light from a green. The blind student must listen to trafÞc to determine when to cross streets as well as direct the dog guide to the desired destination. Since public interference is the greatest distraction to dog guides, users learn to discourage strangers from speaking to or touching the dog while it is in harness.

Applicants for dog guides generally must be legally blind, over 16 years old, able to travel independently, and physically and psychologically able to care for the dog. Although dog guides are often provided free of charge, some training schools require a fee. Most schools will not disqualify an applicant due to lack of funds.

Dog guides generally live and work for 10 years. Dog guides that become sick or disabled are offered to the blind owner to keep as a pet or are returned to the school and placed in an adoptive home. If the dog dies, the blind person may generally return to the school for a new dog. If the dogÕs owner dies, it may remain with the family, be placed with a new dog guide user, or be retired at the school.

dominant eye In normal, healthy eyes, one eye is usually in some degree dominant over the other. Eye dominance follows the same principle as rightor left-handedness and often complies with hand dominance.

In normal vision, both eyes focus on an object. Each eye sends a slightly different view of the sighted object to the brain where the two views are processed into one three-dimensional image. The normally dominant eye is the sighting eye that Þnds and focuses on the object, whereas the non-

dominant eye focuses just off center, the dominant eye is usually used unconsciously to look through a telescope, into a microscope, or through the sight of a camera. To Þnd the dominant eye, punch a hole in a piece of paper and then, without thinking, quickly look through the hole. The eye used to look through the hole is the dominant eye.

Overdominance of one eye may affect or limit vision. If one eye or its muscles are weakened or impaired by conditions such as MYASTHENIA GRAVIS,

MULTIPLE SCLEROSIS, brain tumor, STROKE, or infection, the eyes may become uncoordinated and fail to focus on the same object. When this occurs, DIPLOPIA, or double vision, results.

When one eye turns in (esotropia) or out (exotropia), a condition called STRABISMUS, or crossed-eyes, occurs. The aligned eye becomes the dominant eye over the misaligned eye. Diplopia occurs as a result of strabismus. Strabismus may occur at any age but generally is present in young children. Strabismus may affect over 1.6 million children in the United States.

As the brain receives two images from the misaligned eyes, it relies increasingly on the dominant eye for information about the object viewed. It may begin to suppress the information from the nondominant eye, causing the vision to deteriorate from lack of use of the eye. This condition is known as amblyopia. The suppressed or amblyopic eye may become less functional or lose vision due to lack of light stimulation. Amblyopia usually occurs in young children and affects over 2.5 percent of all children in the United States.

An overdominant eye can often be corrected with surgery to repair or reinforce weakened eye muscles, or with nonsurgical techniques such as glasses, exercise therapy, or patching of the dominant eye. Early diagnosis generally results in the most favorable results.

double vision See DIPLOPIA.

Down’s syndrome DownÕs (or Down) syndrome, or mongolism, is a genetic condition produced by a chromosomal abnormality involving an additional 21st chromosome. DownÕs syndrome is marked by mental retardation, mongoloid facial characteristics,

small stature, heart abnormalities, and obesity. DownÕs syndrome occurs most often in children born to women over 35.

Ocular conditions associated with DownÕs syndrome include high MYOPIA (nearsightedness), hyperplasia of the iris, STRABISMUS, narrow palpebral (eyelid) Þssures, epicanthus (vertical folds of the eyelids), and CATARACT. Cataracts may be slight or serious enough to warrant surgical removal.

dreams Dreams of the blind have long been a subject of interest to psychologists. Research, however, has been sparse, and few investigations have been launched into the activities and objects in dreams of the visually impaired.

Two early studies, Heermann (1838) and Jastrow (1888), drew four major conclusions that are still widely held today. They discovered that no visual images exist in the dreams of the congenitally blind, nor for those blinded before age Þve, but that the dreams of those who become blind between Þve and seven may or may not contain visual imagery and that most optical imagery tends to fade markedly with time.

McCartney (1913) discovered that dreams of the blind contained a high ratio of fearful objects in their dreams when compared with those of sighted subjects. Blank (1958) found that dreams of the blind contained more thought and language than those of sighted subjects, and Von Schumann (1959) related that intellectual activity, dynamic body movement, and falling were characteristic traits of dreams of the visually impaired.

Hall (1966, 1972) proposed that dreams, including those of the blind, must be continuous with waking behavior in that they must reßect actions or conscious thoughts or attitudes. The studies discounted the compensation theory that contends that dreams can embody complete reversals of waking tendencies.

Findings from separate investigations by Kirtley and Cannistraci (1973) and Kirtley and Hall (1975) agreed that the dreams of blind or visually impaired persons differed signiÞcantly from those of sighted persons in regard to the activities and objects found in the dreams. The investigators concluded that these differences are caused by the

physical limitations and Òspecial reality problemsÓ of the blind that exist in their waking life.

Kirtley and Cannistraci created Þve categoriesÑ mobility, aggressive behavior, friendly interactions, self-perception, and perception of the physical environmentÑto describe the differences between the dreams of sighted and visually impaired persons. In their dreams, the visually impaired were more restricted in physical movement, and settings tended to be indoors rather than outdoors.

The dreams of the blind were lower in incidence of physical aggression, yet when incidents did occur, they were unusually extreme. There were few incidents of self-aggression. Verbal aggression incidents were much more frequent than those of sighted subjects. The study showed that the dreams of the blind contained more incidents of friendly speech and thoughts but fewer of friendly acts involving long-term relationships, physical contact, and gift giving.

The study cited more references to body parts and extremities, including the head, and fewer to clothing. Concerning the environment, the study concluded that blind subjects cited fewer incidents of building materials and descriptions of size, including thinness, narrowness, lowness, crookedness, crowding, and vacancy.

Kirtley and Sabo (1979) compared the dreams of visually impaired students, including partially blind, congenitally blind, and adventitiously blind individuals, with those of normally sighted students. The Þndings revealed that the dreams of the visually impaired group as a whole contained less symbolism than those of the sighted subjects. They concluded that the concreteness of the dreams was a result of the fact that blindness is an internalized stress condition that creates more waking-hour reality problems.

Sabo and Kirtley (1982) discovered that blind subjects tended to dream more often about food and drink; parts of the torso; land areas limited by boundaries such as cities, parking lots, yards, and swimming pools; and construction materials such as bricks, lumber, and boards. They concluded that this is a result of how the blind learn their environment and the limitations surrounding their handicap. The study revealed a significant number of active physical activities such

as running, walking, and climbing but the activities tended to take place in a limited area or space.

Kirtley and Sabo (1983) compared the aggression content of dreams of visually impaired females and normally sighted females and found that the visually impaired women exhibited more verbal and covert aggression. These Þndings agreed with the Kirtley and Cannistraci (1973) report that found less physical aggression in the dreams of visually impaired persons (both male and female) but a higher incidence of verbal and covert aggression. Rainville (1994) concluded that dreams are extremely important in the rehabilitation of people who are newly blind. They are vital to a personÕs adjustment to blindness, he says.

Helen Keller described her dreams in her book The World I Live In and in the article ÒMy Dreams.Ó Although edited for print, they reßect the images of the visually impaired.

Keller related that her dreams were Þlled with sensations, odors, tastes, and ideas. She described seeing but not with her eyes and hearing but not with her ears. She explained that she did not often talk with her Þngers or read with her Þngers in dreams and that she possessed greater freedom of mobility.

She recounted seeing a brilliant light of Òßash and glory.Ó Keller mentioned colors such as the Òvelvety green of moss,Ó Òthe soft whiteness of lilies,Ó and the Òdistilled hues and sweetness of a thousand roses.Ó

Keller, Helen. ÒMy Dreams,Ó Century Magazine, vol. 77, no. 1 (1908): pp. 134Ð165.

Keller, Helen. The World I Live In. New York: Century Company, 1908.

Kirtley, Donald, and Katherine Cannistraci. ÒDreams of the Visually Handicapped: Toward a Normative Approach.Ó AFB Research Bulletin #27 (April 1974): 111Ð133.

Kirtley, Donald. The Psychology of Blindness. Chicago: Nel- son-Hall, 1975.

Kirtley, Donald, and Kenneth Sabo. ÒAggression in the Dreams of Blind Women.Ó Journal of Visual Impairment and Blindness, vol. 77, no. 6 (June 1984): 269Ð270.

Kirtley, Donald, and Kenneth Sabo. ÒSymbolism in the Dreams of the Blind.Ó International Journal of Rehabilitation Research vol. 2, no. 2 (1979): 225Ð232.

Rainville, Raymond E. ÒThe Role of Dreams in the Rehabilitation of the Adventitiously Blind.Ó Dreaming (1994): pp. 155Ð164.

Sabo, Kenneth, and Donald Kirtley. ÒObjects and Activities in the Dreams of the Blind.Ó International Journal of Rehabilitation Research, vol. 5, no. 2, (1982): 241Ð242.

drugs Topical and systemic drugs are used in ophthalmology to treat eye diseases and disorders, to prepare eyes of examination or surgery, to treat or prevent inßammation, and to diagnose disease or disorders.

Mydriatics are drugs that dilate the pupils. They are generally either sympathomimetics or parasympatholytics. Sympathomimetics imitate or initiate the release of adrenaline and direct the action to the dilator muscle of the iris. Parasympatholytics dilate the PUPIL and retain it in position so that the pupil cannot accommodate its size to changes in light.

Generic sympathomimetics include phenylephrine HCl, hydroxyamphetamine HBr, and cocaine; trade names include Ak-Dilate, Efricel, Mydfrin, Neo-Synephrine HCl, Penoptic, and Paredrine. Generic parasympatholytics include atropine sulfate, cyclopentolate HCl, homatropine HBr, scopolamine, and tropicamide; trade names include Ak-Pentolate, Cyclogyl, Homatrocel, Isopto Homatropine, Isopto Hyoscine, Mydramide, Mydriacyl, and Topicacyl.

Miotics are parasympathomimetics that are used to treat GLAUCOMA and ESOTROPIA. Cholinergic (direct-acting) miotics include the generic carbachol, pilocarpine hydrochloride, and pilocarpine nitrate, and the trade names Carbacel, Isopto Carbachol, Adsobocarpine, Akarpine, Almocarpine, Isopto Carpine, Pilocar, Pilocel, Pilomiotin, Pilopine gel hs 4 percent, Ocusert Pilo, Piloptic, and P.V. Carpine. Anticholinesterasic (indirect acting) miotics include the generic physostigmine sulfate, physostigmine salicylate, demecarium bromide, echothiophate iodide and isoßurophate (DFP), and the trade names Eserine Sulfate, Isopto Eserine, Humorsol, Echodide, Phospholine Iodide and Floropryl.

Ocular infections are treated according whether the infecting agent is bacterial, fungal, viral, or pro-

tozoal. Antibiotics are used to treat corneal ulcers and intraocular infections. Antibiotics may be topical or systemic and include the generic ampicillin, bacitracin, carbenicillin, cefazolin, cephalothin, chloramphenicol, clindamycin, colistin sulfate, erythromycin, gentamycin sulfate, lincomycin, methicillin, neomycin, penicillin, polymyxin B sulfate, silver nitrate, streptomycin, sulfacetamide sodium, sulÞsoxazole diolamine, tetracycline, tobramycin, and vancomycin. They are known by numerous trade names, including Baciquent, Ak-Lor, Antibiopto, Coly-Mycin S. Ilotycin, Garamycin, Genoptic, Aerosporin, Ak-Sulf, Gantrisin, Achromycin, and Tobrex.

Antifungal drugs are used to treat infections such as fungal KERATITIS and fungal ENDOPHTHALMI- TIS. Generic antifungal agents include amphotericin B, nystatin, ßucytosine, natamycin, miconazole, and ketoconazole.

Antiviral drugs are used to treat infections such as HERPES SIMPLEX. Generic antiviral drugs include idoxuridine, trißuridine, vidarabine (ARA), and acyclovir; trade names for these drugs include Dendrid, Herplex LiquiÞlm, Stoxil, Viroptic, Vira-A, and Zovirax. Two antiviral drugs, ganciclovir and foscarnet, are used to treat cytomegalovirus retinitis, an infection of the retina associated with AIDS.

Antiprotozoal drugs are used to treat some types of UVEITIS. These drugs include Pyrimethamine, Sulfadiazine, Clindamycin, and corticosteroid preparations.

Anti-inflammatory drugs are used to treat inßammatory disorders such as BLEPHARITIS, CON-

JUNCTIVITIS, KERATITIS, SCLERITIS, uveitis, and optic neuritis. Corticosteroids are often prescribed under the generic names hydrocortisone, prednisolone, dexamethasone, and progesteronelike compounds. Trade names for these drugs include Hydrocortone acetate, Optef drops, Pred Mild/Pred Forte, Inßamase, Ak-Dex, Decadron, Maxidex, HMS, and FML.

Anesthetic drugs may be topical or regional. They allow the physician to perform procedures on the eye. Topical anesthesia includes the generic cocaine hydrochloride, proparacaine hydrochloride and tetracaine hydrochloride, and the trade names Ak-taine, Alcaine, Ophthaine, Ophthetic, Anacel, and Pontocaine. Regional anesthetics include Tetra-

caine, Procaine, Hexylcaine, Bupivacaine, Lidocaine, Mepivacaine, Prilocaine, and Etidocaine.

Drugs used to treat glaucoma include sympathomimetics and parasympathomimetics, which increase the ßow of AQUEOUS FLUID from the eye; adrenergic antagonists and carbonic anhydrase inhibitors, which decrease the aqueous ßuid supply; and hyperosmotic agents, which decrease intraocular pressure.

Adrenergic agents include the generic epinephrine bitartrate, epinephrine hydrochloride, epinephrine borate, dipivefrin hydrochloride, timolol maleate, levobunolol, and betaxolol. Trade names include E, Epitrate, Mytrate, Murocoll, Epifrin, Glaucon, Epinal, Eppy/N, Propine, Timoptic, Betagan, and Betoptic.

Carbonic anhydrase inhibitors include the generic acetazolamide, acetazolamide sodium, dichlorphenamide, and methazolamide, and trade names Ak-Zol, Cetazol, Diamox, Daranide, Oratrol, and Neptazane. Hyperosmotic agents include the generic glycerin, isosorbide, mannitol, and urea and the trade names Glyrol, Osmoglyn, Ismotic, Osmitrol, and Ureaphil.

ArtiÞcial tears are used to treat dry eye conditions. These drugs are known by the generic hydroxyethylcellulose, hydroxyproplycellulose, hydroxypropl methylcellulose, methylcellulose, polyvinyl alcohol, and other polymeric solutions. Numerous trade names include Clerz, Lacrisert, Isopto Alkaline, Muro Tears, Methopto, Methulose, Aqua Tears, LiquiÞlm Tears, aqua-FLOW, Refresh, Adapettes, Comfort Drops, and Hypotears.

Drugs are used in procedures to examine or test the eyes and diagnose disorders. Small strips of paper impregnated with ßuorescein dye are used to test the CONJUNCTIVA and corneal epithelium. Sodium ßuorescein is injected intravenously to study the circulation of blood in the RETINA and

CHOROID.

Rose bengal is a solution used to test the conjunctiva and corneal epithelium for unhealthy cells.

Doctors and scientists are working hard to Þnd new drugs to treat vision disorders, and new uses for existing drugs. One of these promising drugs is Visudyne, approved by the U.S. Food and Drug Administration in April 2000 and used in the

treatment of the wet form of age-related macular degeneration. Representatives of the American Academy of Ophthalmology said they are hopeful that Visudyne will be the start of a new era in treating a leading cause of blindness among older people.

American Academy of Ophthalmology Medical Library.

American Academy of Ophthalmology Says Newly Approved Drug, Visudyne, Is Promising. 2000.

Henkind, Paul, Martin Mayers and Arthur Berger, eds.

Physicians’ Desk Reference for Ophthalmology 1987.

Oradell, N.J.: Medical Economics Company Inc., 1987.

dry eye Dry eye is a condition in which the eye lacks the necessary amount or quality of tears. Tears protect, nourish, and moisturize the eye. Without proper tear function, the CORNEA and CON- JUNCTIVA may become dry and develop disorders.

In the normal eye, the tear Þlm is made up of three layers that are produced by the lacrimal gland and accessory lacrimal glands and cells. The lacrimal glands are located in the orbit and inner eyelid. The accessory glands and cells are located in the conjunctiva.

The top layer of tears is formed by the secretion of the meibomian glands and is oily in nature. The second layer is composed of watery tears from the lacrimal glands, and the third layer, which lies next to the cornea, is of mucuslike consistency and is produced by accessory glands. The layers are maintained by constant blinking and are all necessary for proper health of the eye.

Dry eye may occur as a result of poor tear production (called keratoconjunctivitis sicca), poor tear quality, or inadequate blinking, which leaves the eye open to the drying elements or does not properly wet the entire surface of the eye. Conditions that can cause dry eye include sarcoidosis, rheumatoid arthritis, vitamin A deÞciency, pemphigoid, trachoma, Stevens-Johnson syndrome, chemical burns, neuroparalytic and exposure keratitis, and aging.

Dry eye may lead to corneal damage, permanent corneal scarring, and opacification. Once the cornea has opaciÞed, vision is lost. Symptoms of dry eye include redness, discomfort or irritation,

decreased corneal luster, and loss of visual acuity. Dry eyes can become extremely sensitive to wind, low humidity, heating, air conditioning, and so forth. Excess tearing may occur if the tears produced are inadequate in quality.

Dry eye is diagnosed through a thorough eye examination, including a slit-lamp examination, a SchirmerÕs test, and a tear film break-up test. The slit lamp is used to examine the tear film for the presence of extraneous microscopic filaments, epithelial cells, and corneal erosion that are apparent and will stain when exposed to rose bengal.

The SchirmerÕs test involves inserting one end of of a narrow strip of paper into the lower lid. The strip is left in place for Þve minutes during which time it absorbs tears. At the end of the time, the strip is removed and measured for the amount of tears present. Dry eye may be indicated if the measurement is less than 10 millimeters.

During the tear-Þlm break-up test, the tear Þlm is watched to determine the time needed to break the Þlm once the blinking has stopped. The tears are stained with ßuorescein dye and the eye is held open. In cases of dry eye, the tear Þlm may break in less than 10 seconds.

Treatment of dry eye includes treating the underlying cause or disease and the administration of artiÞcial tears. In some cases, antibiotics may be prescribed and the use of home vaporizers or humidiÞers advised.

Surgery may be performed to close the tear drainage ducts to ensure better utilization of reduced tear production. If the cornea is severely scarred and vision is lost, a CORNEAL TRANSPLANT or keratoplasty may be indicated. However, those with dry-eye conditions are generally poor candidates for a successful corneal transplantation. Some

medications that stimulate tear production are being investigated.

Duxbury Systems, Inc. A company formed in 1975 to develop braille software for minicomputers. Two of Duxbury SystemsÕs founders, Robert Gildea and Joseph Sullivan, were members of a team that in 1970 developed DOTSYS III, the Þrst braille translator written in a portable programming language. DOTSYS III was developed for the Atlanta Public School system.

In 1975, Gildea, Sullivan, and their partner Anne Simpson developed the Duxbury Braille Translator, which was capable of translating braille in six languages.

Since 1975, Duxbury Systems has become a world leader in software for braille with Windows, Macintosh, DOS, and Unix programs. The Duxbury Braille Translator and MegaDots, a program developed by a company called Braille Planet, originally Raised Dot Computing, continue to be the companyÕs ßagship products.

Duxbury acquired the Madison, WisconsinÐ based Braille Planet in August 1999. Raised Dot Computing, founded in 1981, produced software that enabled transcribers to produce braille books and create graphics using an Apple computer. It also provided on-line electronic Braille libraries and educational services, and produced and distributed materials relating to blindness issues.

Contact:

Duxbury Systems, Inc. 270 Littleton Road, Unit 6 Westford, MA 01886-3523 978-692-3000 (ph) 978-692-7912 (fax) www.duxburysystems.com

A term used to describe programs and services offered to families of visually impaired children and preschools for visually impaired children. They provide information on home management and educational child-develop- ment skills and opportunities for children to develop skills and participate in socialization. The programs work closely with parents to maximize the potential for growth and development among these children. Services vary and may include home visitations, small group instruction, and community facilities programs.

The Individuals with Disabilities Education Act was signed into law in 1997. Formerly known as the Education of the Handicapped Act, the law mandates that services, such as early intervention programs, vision services, assistive technology and services, and transportation be provided for threeto Þve-year-old children with disabilities, including visual impairment.

The intent of the act is to provide appropriate public education to all eligible children. Schools must comply with the regulations of the act in order to receive certain funding.

echolocation See SENSES.

ectropion A disorder of the eyelids in which the lower lid turns outward. Ectropion is generally caused by aging but may result from scarring of the eyelids or nerve palsy. The exposure of the inner lid may cause tearing, irritation, and conjunctivitis.

Ectropion can be corrected with minor outpatient surgery using a local anesthetic. During the procedure, a portion of the sagging lid or scar tissue may be removed. Skin grafting may be required. Corrective surgery for ectropion may result in an

E

overor undercorrection of the problem. Complications may include bleeding, infection, or recurrence.

education Formal education of the visually impaired prior to the middle 1700s was a private matter, lacking in systematic programs or educational formats. Many who lacked educated advocates or resources were not educated at all.

The Þrst school for blind children, the Institution des Jeunes Aveugles (Institute for Blind Youth), was established in 1784 in Paris by Valentin Hauy. The residential school presented a curriculum orally and through embossed print or enlarged raised letters, read tactually.

In 1824, Louis Braille, one of the schoolÕs students, developed the BRAILLE method of communication. Braille is a tactually read language involving a series of conÞgurations of raised dots based on a six-dot cell. The braille method made writing possible and reading more accessible to those with vision impairments and revolutionized the ability of blind students to obtain an education.

In the early 1800s, the Þrst three schools for the blind were founded in the United States. In 1829, the New England Asylum for the Blind, later renamed the Perkins School for the Blind, was incorporated and opened in 1832 under the direction of Samuel Gridley Howe. In 1831, the New York Institution for the Blind, later renamed the New York Institute for the Blind, opened under the direction of Dr. John Dennison Russ. The Pennsylvania Institution for the Instruction of the Blind, now named the Overbrook School for the Blind, was started by Quakers in 1833 under the directorship of Julius R. Friedlander.

The schools were residential, privately Þnanced, and based on the programs offered by the Institute