Text . Protective Features and Blindness

 

The structures around the eye protect it while allowing it to move freely in all directions. They protect the eye, which is constantly exposed to dust, wind, bacteria, viruses, fungi, and other potentially injurious substances, while allowing it to remain open enough to catch light rays.

The orbits are bony cavities containing the eye­balls, muscles, nerves, blood vessels, fat, and structures that produce and drain tears. The eye­lids, thin folds of skin, cover the eyes. They reflexively close quickly to protect the eye from for­eign objects, wind, dust, and very bright light. When blinked, the eyelids help spread liquid over the surface of the eyes, and when closed, they help keep the surface moist. Without such mois­ture, the normally transparent cornea can be­come dried, injured, and opaque.

The inner surface of the eyelid is a thin mem­brane (conjunctiva) that loops back to cover the surface of the eye. The eyelashes are short hairs growing from the edge of the eyelid that help protect the eye by acting as a barrier. Small glands at the edge of the eyelid secrete an oily substance that contributes to the tear film and keeps tears from evaporating.

The lacrimal glands, located at the top outer edge of each eye, produce the watery portion of tears. Tears drain from the eyes into the nose through the two nasolacrimal ducts; each of these ducts has openings at the edge of the upper and lower eyelids near the nose. Tears keep the sur­face of the eye moist and healthy; they also trap and sweep away small particles that enter the eye. Moreover, tears are rich in antibodies that help prevent infection.

Both eye injury and disease can affect vision. The clarity of vision is called visual acuity, which ranges from full vision to no vision. As acuity de­creases, vision becomes progressively blurred. Acuity is usually measured on a scale that com­pares a person's vision at 20 feet with that of someone who has full acuity. Thus, a person who has 20/20 vision sees objects 20 feet away with complete clarity, but a person who has 20/200 vision sees at 20 feet what a person with full acuity sees at 200 feet.

Legal blindness is defined as visual acuity worse than 20/200 even after correction with eye-glasses or contact lenses. Many people who are considered legally blind can distinguish shapes and shadows but not normal detail.

Causes

Blindness can occur for any of the following reasons:

light can't reach the retina

light rays don't focus properly on the retina

the retina can't sense light rays normally

the nerve impulses from the retina aren't transmitted to the brain normally

the brain can't interpret information sent by the eye.

Several disorders can cause these problems that lead to blindness. A cataract can block light coming into the eye, so that it never reaches the retina. Focusing (refraction) errors can usually be corrected with prescription lenses but not always completely. A detached retina and hereditary disorders such as retinitis pigmentosa can affect the retina's ability to sense light. Diabetes or macular degeneration can also damage the retina. Disorders of the nervous system such as multiple sclerosis or inadequate blood supply can damage the optic nerve, which carries impulses to the brain. Tumors in nearby structures, such as the pituitary gland, also can damage this nerve. The areas of the brain that interpret visual impulses may be damaged by stroke, tumor, or other disease.

Common Causes of Blindness Cataract 1. Most common cause 2. Can be cured with surgery Infection Most common preventable cause in the world Not common in United States Diabetes 1. One of most common causes in United States 2. Often preventable 3. Laser treatment slows vision loss Macular degeneration · Affects central vision, not peripheral vision Preventable and treatable in fewer than 10 percent of people Glaucoma · Highly treatable · If treated early, should not lead to blindness

 

Notes:

eyeball	глазное яблоко
blink	моргать
trap	останавливать, задерживать
visual acuity	острота зрения
retinitis pigmentosa	пигментная дегенерация сетчатки
eyelashes	ресницы
sweep away	сметать, уничтожать
blurry	неясный, туманный; расплывчатый

 

 

Refractive Disorders

 

Normally, the eye creates a clear image because the cornea and lens bend (refract) incoming light rays to focus them on the retina. The shape of the cornea is fixed, but the lens changes shape to fo­cus on objects at various distances from the eye. The shape of the eyeball further helps to create a clear image on the retina.

People who are farsighted (hyperopic) have trouble seeing anything close, and those who are nearsighted (myopic) have trouble focusing or distant objects. As people reach their early 40s the lens becomes increasingly stiff, so that it can't focus on nearby objects, a condition called presbyopia. If a person has had a lens removed to treat cataracts but hasn't had a lens implant, objects look blurred at any distance; the absence of a lens is called aphakia. An imperfectly shaped cornea may cause visual distortion from astigmatism.

Everyone should have regular eye examinations by a family doctor, internist, ophthalmologist, or optometrist. The eyes are tested together and individually. Vision testing usually also in­cludes assessments unrelated to refractive error, such as a test of the ability to see colors.

Treatment

The usual treatment for refractive errors is to wear corrective lenses. However, certain surgical procedures and laser treatments that change the shape of the cornea also can correct refractive errors.

Text A. Corrective Lenses

Refractive errors can be corrected with glass or plastic lenses mounted in a frame (eyeglasses) or with small pieces of plastic placed directly over the cornea (contact lenses). For most people, the choice is a matter of appearance, convenience, and comfort. Plastic lenses for eyeglasses are lighter but tend to scratch; glass lenses are more durable but more likely to break. Both types can be tinted or treated with a chemical that darkens them automatically on exposure to light. Lenses can also be coated to reduce the amount of potentially damaging ultraviolet light that reaches the eye. Bifocals contain two lenses—an upper lens that correct nearsightedness and a lower lens that corrects farsightedness.

Many people think contact lenses are more attractive than eyeglasses, and some think that vision is more natural with contact lenses. However, contact lenses require more care than glasses, they may damage the eye, and they can't correct vision for some people as well as eyeglasses can. The elderly and people with arthritis may have trouble handling contact lenses and placing them in their eyes.

Hard (rigid) contact lenses are thin disks made of hard plastic. Gas-permeable lenses, made of silicone and other compounds, are rigid but per­mit better oxygen transport to the cornea. Soft hydrophilic contact lenses made of flexible plastic are larger and cover the entire cornea. Most soft, nonhydrophilic lenses are made of silicone.

Elderly people generally find soft lenses easier to handle because they're larger. They're also less likely than rigid lenses to fall out or to allow dust and other particles to get trapped underneath. Plus, soft contact lenses are usually comfortable on the first wearing. They do, however, require scrupulous care.

Most contact lenses must be removed and cleaned every day. As an alternative, a person can use disposable lenses—some of which are replaced every week or two, others of which are replaced every day. Using disposable lenses avoids the need to clean and store lenses because each lens is regularly replaced with a fresh one.

Wearing any type of contact lenses poses a risk of serious, painful complications, including corneal ulceration from an infection, which can lead to a loss of vision. The risks can be greatly reduced by following the instructions of the manufacturer and the eye doctor and by using common sense. All reusable contact lenses must be sterilized and disinfected; enzyme cleaning is no substitute for sterilizing and disinfecting. The risk of serious infections increases from cleaning contact lenses with homemade saline solution, saliva, tap water, or distilled water and from swimming while wearing contact lenses. A person shouldn't wear soft contact lenses—including daily wear, extended wear, or disposable types—to bed at night, unless there's a special reason for doing so. If a person experiences discomfort, excessive tearing, vision changes, or eye redness, the lenses should be removed immediately. If the symptoms don't resolve quickly, the person should contact an eye doctor.

Surgery and Laser Therapy. Certain surgical and laser procedures (refractive surgery) can be used to correct nearsightedness, farsightedness, and astigmatism. However, these procedures don't usually correct vision as well as glasses and contact lenses do. Before deciding on such a procedure, a person should have a thorough discussion with an ophthalmologist and should carefully consider the risks and benefits.

The best candidates for refractive surgery are people whose vision can't be corrected by eye-glasses or contact lenses and people who can't tolerate wearing them. However, many people undergo this surgery for convenience and cosmetic purposes, and many are satisfied with the outcome.

Radial and astigmatic keratotomy. Keratotomy is a surgical procedure used to treat nearsightedness and astigmatism. In radial keratotomy, the surgeon makes small radial (or wheel spoke) cuts in the cornea. Usually, four to eight cuts are made. In astigmatic keratotomy, which is used to correct naturally occurring astigmatism and astigmatism after cataract surgery or corneal transplant, the surgeon uses perpendicular cuts. Because the cornea is only 1/2 millimeter in thickness, the depth of the cuts must be determined precisely. The surgeon determines where to make each cut after analyzing the shape of the cornea and the person's visual acuity.

The surgery flattens the cornea, so it can better focus incoming light on the retina. This change improves vision, and about 90 percent of those who have the surgery can function well and drive without their glasses or contact lenses. Sometimes, a second or third touch-up procedure is needed to improve vision sufficiently.

No surgical procedure is risk free, but the risks from radial and astigmatic keratotomy are small. The major risks are overcorrection and undercorrection of the vision problem. Because overcorrection usually can't be treated effectively, a surgeon tries to avoid doing too much correction at anyone time. As mentioned, undercorrection can be addressed by a second or third touch-up procedure. The most serious complication is infection, which develops in far less than 1 percent of cases. When it does develop, it must be treated with antibiotics.

 

Notes:

farsighted	дальнозоркий
farsightedness	гиперметропия, дальнозоркость
nearsightedness	близорукость, миопия
nearsighted	близорукий
distortion	искажение; искривление
durable	надежный, прочный
disposable	одноразовый
reusable	многократного пользования
overcorrection	гиперкоррекция
under correction	недостаточная коррекция

 

Eye injuries

The structure of the face and eyes is well suited for protecting the eyes from injury. The eyeball is set into a socket surrounded by a strong, bony ridge. The eyelids can close quickly to form a barrier to foreign objects, and the eye can tolerate a light impact without damage. Even so, the eye and its surrounding structures can be damaged by injury, sometimes so severely that vision is lost, and in rare instances, the eye must be removed. Most eye injuries are minor, but because of extensive bruising, they often look worse than they are. Any injury to the eye should be examined by a doctor to determine whether treatment is needed and whether the eyesight may be affected permanently.

Text A. Blunt Injuries

 

A blunt impact forces the eye back into its socket, possibly damaging the structures at the surface (the lid, conjunctiva, sclera, cornea, and lens) and those at the back of the eye (retina and nerves). Such an impact may break bones around the eye as well.

Symptoms

In the first 24 hours after an eye injury, blood leaking into the skin around the eye usually produces a bruise (contusion), commonly called a black eye. If a blood vessel on the surface of the eye breaks, the surface will become red. Such bleeding is usually minor.

Damage to the inside of the eye is often more serious than damage to the surface. Bleeding into the front chamber of the eye (anterior chamber hemorrhage, traumatic hyphema) is potentially serious and requires attention by an eye doctor (ophthalmologist). Recurring bleeding and increased pressure within the eye may lead to blood staining of the cornea, which can reduce vision much as a cataract does, and increase the lifelong risk of glaucoma.

Blood can leak into the inside of the eye, the iris (the colored part of the eye) can be torn, or the lens can become dislocated. Bleeding may occur in the retina, which may become detached from its underlying surface at the back of the eye.

Initially, retinal detachment may create images of irregular floating shapes or flashes of light and may make vision blurry, but then vision greatly decreases. In severe injuries, the eyeball can rupture.

Treatment

Ice packs may help reduce swelling and ease the pain of a black eye. By the second day, warm compresses can help the body absorb the excess blood that has accumulated. If the skin around the eye or on the lid has been cut (lacerated), stitches may be needed. When possible, stitches near the edge of the eyelids should be applied by an eye surgeon to ensure that no deformities develop that will affect the way the lids close. An injury affecting the tear ducts should be repaired by an eye surgeon.

For a laceration of the eye, pain medications may be given along with medications to keep the pupil dilated and to prevent infection. A metal shield is often used to protect the eye from further injury. Serious damage may result in some loss of sight, even after surgical treatment.

Anyone who has internal bleeding in the eye caused by trauma is instructed to rest in bed. A medication to reduce increased eye pressure, such as acetazolamide, may be needed. Sometimes an additional medication, aminocaproic acid, is given to reduce bleeding. Any medication that contains aspirin should be avoided because aspirin can increase internal bleeding in the eye. People taking warfarin or heparin to keep their blood from clotting or aspirin for any reason should tell the doctor immediately. Rarely, recurring bleeding requires surgical drainage by an ophthalmologist.

 

Notes:

socket	углубление
eyesight	зрение
tear	рвать(ся), разрывать(ся)
detachment	отделение, отслойка
lacerate	рвать, раздирать, разрывать
pupil	зрачок
dilate	расширять(ся)

 

Text B. Foreign Objects

 

The most common eye injuries are those to the sclera, cornea, and lining of the eyelids (conjunctiva) caused by foreign objects. Although most of these injuries are minor, some - such as penetration of the cornea or development of an infection from a cut or scratch on the cornea - can be serious.

Perhaps the most common source of surface injuries is the contact lens. Poorly fitting lenses, lenses left in the eyes too long, lenses left in while a person sleeps, inadequately sterilized lenses, and forceful or inept removal of lenses can scratch the surface of the eye. Other causes of surface injuries include glass particles, wind-borne particles, tree branches, and falling debris. Workers in certain occupations tend to have small particles fly in their faces; these workers should wear protective eyewear.

Symptoms

Any injury to the surface of the eye usually causes pain and a feeling that there's something in the eye. It may also produce a sensitivity to light, redness, bleeding from the surface blood vessels of the eye, or swelling of the eye and eye­lid. Vision may become blurred.

Treatment

A foreign object in the eye must be removed. Special eyedrops containing fluorescein dye make the object more visible and reveal any surface abrasions. Anesthetic drops may be instilled to numb the surface of the eye. Using a special lighting instrument to view the surface in detail, the doctor then removes the object. Often the foreign object can be lifted out with a moist sterile cotton swab. Sometimes it can be flushed out with sterile water.

If the foreign object has produced a small, superficial corneal abrasion, an antibiotic ointment applied for several days may be all the treatment needed. Larger corneal abrasions require additional treatment. The pupil is kept dilated with medications, antibiotics are instilled, and a patch is placed over the eye to keep it closed. Fortunately, the surface cells of the eye regenerate rapidly. Under a patch, even large abrasions tend to heal in 1 to 3 days. If the foreign object has pierced the deeper layers of the eye, an ophthalmologist should be consulted immediately for emergency treatment.

 

Notes:

scratch	ссадина, царапина
inept	несвоевременный, неуместный
swab	тупфер
abrasion	ссадина, царапина
patch	бляшка

 

Text C. Burns

 

Exposure to strong heat or chemicals makes the eyelids close quickly in a reflex reaction to protect the eyes from burns. Thus, only the eyelids may be burned, although extreme heat can also burn the eye itself. The severity of the injury, the amount of pain, and the appearance of the eyelids depend on the depth of the burn.

Chemical burns can occur when an irritating substance gets into the eye. Even mildly irritating substances can cause substantial pain and damage the eye. Because the pain is so great, there's a tendency to keep the eyelids closed, thereby keeping the substance against the eye for a prolonged period.

Treatment

To treat burns on the eyelids, a health care practitioner washes the area with a sterile solution and then applies an antibiotic ointment or a strip of gauze saturated with petroleum jelly. The treated area is covered with sterile dressings held in place with a plastic bandage or stockinette to allow the burn to heal.

A chemical burn of the eye is treated by immediately flooding the open eye with water. This treatment must be started even before trained medical personnel arrive. Although a person may have difficulty keeping the injured eye open during this painful treatment, quick removal of the chemical is essential. A doctor may begin treatment by instilling anesthetic drops and medication to keep the pupil dilated. Antibiotics are usually used in ointment form. Oral analgesics may also be needed. Severe burns may need to be treated by an ophthalmologist to preserve vision and prevent major complications, such as damage to the iris, perforation of the eye, and deformities of the eyelids. However, even with the best treatment, severe chemical burns of the cornea can lead to scarring, perforation of the eye, and blindness.

Notes:

health care	здравоохранение
gauze	марля
stockinet	трикотаж

 

Eye Socket Disorders

 

The eye sockets (orbits) are bony cavities that contain and protect the eyes. Disorders affecting the orbits include fractures, orbital cellulitis, cavernous sinus thrombosis, and exophthalmos.

Text.

Fractures. An injury to the face can fracture any of several bones that form the orbits. Although a facial fracture usually doesn't impair vision, certain fractures can.

Blood that accumulates after a fracture can put pressure on the eye or on the nerves and blood vessels going to and from it. The fracture may also impair the function of the muscles that move the eye, producing double vision or inhibiting eye movement to the right, left, up, or down. Rarely, a fragment of broken bone presses on or cuts into a nerve, blood vessel, or muscle, impairing eye movement and vision.

When a fracture traps nerves or muscles or pushes the eyeball backward, a repair of the facial bones—usually a surgical repair—is necessary. After ensuring that the fracture hasn't damaged a vital structure, the surgeon restores the bones to their proper position, using small metal plates and screws or wires.

Orbital cellulitis is an infection of the tissues around the eyeball.

The infection may spread from the sinuses, teeth, or bloodstream or it may develop after an eye injury. Symptoms of orbital cellulitis include extreme pain, bulging eyes, reduced eye movement, swollen eyelids, fever, and a swollen, hazy appearance of the eyeball. If not adequately treated, orbital cellulitis can lead to blindness, infection of the brain and spinal cord, and blood clots in the brain.

Diagnosis and Treatment

Doctors can usually recognize orbital cellulitis without using diagnostic tests. However, determining the cause may require further assessment, including examinations of the teeth and mouth as well as x-rays or computerized tomography (CT) scans of the sinuses. Often, doctors obtain samples from the lining of the eye and from the skin, blood, throat, or sinuses and send them to the laboratory to be cultured. These tests help determine which type of bacteria is causing the infection and which treatment should be used.

Oral antibiotics are given for mild cases; intravenous antibiotics are given for severe cases. The antibiotic used at first may be changed if the culture results suggest that another one will be more effective. Sometimes surgery is needed to drain a pocket of infection (abscess) or an infected sinus.

Cavernous sinus thrombosis is the blockage of a large vein at the base of the brain (the cavernous sinus), usually caused by the spread of bacteria from a sinus infection or an infection around the nose.

An infection may spread from a sinus or the area of skin around the nose or eye to the brain either directly or through veins. This infection causes bulging eyes, severe headache, coma, seizures, and other nervous system abnormalities, along with a high fever.

Fortunately, cavernous sinus thrombosis is very rare. About 30 percent of people who have it die, and many who survive are left with serious mental or neurologic handicaps despite medical treatment.

Diagnosis and Treatment

To diagnose cavernous sinus thrombosis and identify the bacteria causing the infection, a doctor takes a blood sample and samples of fluid, mucus, or pus from the throat and nose and sends them to the laboratory to be cultured. Also, a computed tomography (CT) scan of the sinuses, eyes, and brain is usually performed.

High doses of intravenous antibiotics are given immediately. If the condition doesn't improve after 24 hours of antibiotic treatment, the sinus may be drained surgically.

Exophthalmos is an abnormal bulging of one or both eyes.

All people with protruding eyes don't necessarily have exophthalmos. Some people simply have prominent eyes with whiter showing than normal. The extent of the protrusion can be measured in an eye doctor's (ophthalmologist's) of­fice with an ordinary ruler or with an instrument called an exophthalmometer. Further diagnostic tests may include a computed tomography (CT) scan and thyroid function tests.

Many conditions can cause exophthalmos. In some types of thyroid disease, especially Graves' disease, the tissues in the eye socket swell, and deposits of unusual material push the eyeball forward. Exophthalmos can occur suddenly from bleeding behind the eye or from inflammation in the eye socket. Tumors, either cancerous or noncancerous, can form in the eye socket behind the eyeball and push it forward. An unusual growth of tissue (pseudotumor) may produce exophthalmos in 2 to 3 weeks. Cavernous sinus thrombosis causes swelling from the backup of blood in the veins exiting the eye. Abnormal connections of the arteries and veins (arteriovenous malformations) behind the eye may produce a pulsating exophthalmos, in which the eye bulges forward and pulses along with the heartbeat.

Treatment

The treatment depends on the cause. If the problem is an abnormality between arteries and veins, surgery may be needed. If too much thyroid hormone is being produced (hyperthyroidism) the bulging may subside when hyperthyroidism is controlled. Occasionally, however, exophthalmos persists even when the thyroid disease has been controlled. If the optic nerve is being compressed, oral corticosteroids, local radiation therару, or surgery is needed to ease the pressure. If the eyelids don't properly cover the bulging eyeball, eyelid surgery may be needed to help protect the cornea from drying and infection. Corticosteroids may help in treating pseudotumor and swelling. If tumors threaten the eye by pushing it forward, they may be removed surgically.

 

Notes:

bulging eyes	глаза навыкате
hazy	туманный, неясный
seizure	судорога
Graves' disease	базедова болезнь
eye socket	орбита
backup	застой, нарушение оттока