Q:Information:  - Glaucoma is a group of eye diseases which result in damage to the optic nerve and vision loss. The most common type is open-angle glaucoma with less common types including closed-angle glaucoma and normal-tension glaucoma. Open-angle glaucoma develops slowly over time and there is no pain. Side vision may begin to decrease followed by central vision resulting in blindness if not treated. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from glaucoma, once it has occurred, is permanent. Risk factors for glaucoma include increased pressure in the eye, a family history of the condition, migraines, high blood pressure, and obesity. For eye pressures a value of greater than is often used with higher pressures leading to a greater risk. However, some may have high eye pressure for years and never develop damage. Conversely, optic nerve damage may occur with normal pressure, known as normal-tension glaucoma. The mechanism of open-angle glaucoma is believed to be slow exit of aqueous humor through the trabecular meshwork while in closed-angle glaucoma the iris blocks the trabecular meshwork. Diagnosis is by a dilated eye examination. Often the optic nerve shows an abnormal amount of cupping. If treated early it is possible to slow or stop the progression of disease with medication, laser treatment, or surgery. The goal of these treatments is to decrease eye pressure. A number of different classes of glaucoma medication are available. Laser treatments may be effective in both open-angle and closed-angle glaucoma. A number of types of glaucoma surgeries may be used in people who do not respond sufficiently to other measures. Treatment of closed-angle glaucoma is a medical emergency. About 11 to 67 million people have glaucoma globally. The disease affects about 2 million people in the United States. It occurs more commonly among older people. Closed-angle glaucoma is more common in...  - Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some also include those who have a decreased ability to see because they do not have access to glasses or contact lenses. Visual impairment is often defined as a best corrected visual acuity of worse than either 20/40 or 20/60. The term blindness is used for complete or nearly complete vision loss. Visual impairment may cause people difficulties with normal daily activities such as driving, reading, socializing, and walking. The most common causes of visual impairment globally are uncorrected refractive errors (43%), cataracts (33%), and glaucoma (2%). Refractive errors include near sighted, far sighted, presbyopia, and astigmatism. Cataracts are the most common cause of blindness. Other disorders that may cause visual problems include age related macular degeneration, diabetic retinopathy, corneal clouding, childhood blindness, and a number of infections. Visual impairment can also be caused by problems in the brain due to stroke, prematurity, or trauma among others. These cases are known as cortical visual impairment. Screening for vision problems in children may improve future vision and educational achievement. Screening adults without symptoms is of uncertain benefit. Diagnosis is by an eye exam. The World Health Organization (WHO) estimates that 80% of visual impairment is either preventable or curable with treatment. This includes cataracts, the infections river blindness and trachoma, glaucoma, diabetic retinopathy, uncorrected refractive errors, and some cases of childhood blindness. Many people with significant visual impairment benefit from vision rehabilitation, changes in their environmental, and assistive devices. As of 2012 there were 285 million people who were visually impaired of which 246 million had low vision and 39 million were blind. The majority of people with poor vision are in the developing world and are over...  - A cataract is a clouding of the lens in the eye leading to a decrease in vision . It can affect one or both eyes . Often it develops slowly . Symptoms may include faded colors , blurry vision , halos around light , trouble with bright lights , and trouble seeing at night . This may result in trouble driving , reading , or recognizing faces . Poor vision may also result in an increased risk of falling and depression . Cataracts are the cause of half of blindness and 33 % of visual impairment worldwide . Cataracts are most commonly due to aging , but may also occur due to trauma , radiation exposure , be present from birth , or occur following eye surgery for other problems . Risk factors include diabetes , smoking tobacco , prolonged exposure to sunlight , and alcohol . Either clumps of protein or yellow - brown pigment may be deposited in the lens reducing the transmission of light to the retina at the back of the eye . Diagnosis is by an eye examination . Prevention includes wearing sunglasses and not smoking . Early on the symptoms may be improved with eyeglasses . If this does not help , surgery to remove the cloudy lens and replace it with an artificial lens is the only effective treatment . Surgery is only needed if the cataracts are causing problems . Surgery generally results in an improved quality of life . Cataract surgery is not easily available in many countries , which is especially true for women , those living in rural areas , and those who can not read . About 20 million people globally are blind due to cataracts . It is the cause of about 5 % of blindness in the United States and nearly 60 % of blindness in parts of Africa and South America . Blindness from cataracts occurs in about 10 to 40 per 100,000 children in the developing world and 1 to 4 per 100,000 children in the developed world . Cataracts become more common with age . About half the people in the United States have had cataracts by the age of 80 .  - Sunglasses or sun glasses are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can sometimes also function as a visual aid, as variously termed spectacles or glasses exist, featuring lenses that are colored, polarized or darkened. In the early 20th century, they were also known as sun cheaters (cheaters being an American slang term for glasses).  - Infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to these organisms and the toxins they produce. Infectious disease, also known as transmissible disease or communicable disease, is illness resulting from an infection. Infections are caused by infectious agents including viruses, viroids, prions, bacteria, nematodes such as parasitic roundworms and pinworms, arthropods such as ticks, mites, fleas, and lice, fungi such as ringworm, and other macroparasites such as tapeworms and other helminths.  - Trachoma, also called granular conjunctivitis, Egyptian ophthalmia, and blinding trachoma, is an infectious disease caused by bacterium "Chlamydia trachomatis". The infection causes a roughening of the inner surface of the eyelids. This roughening can lead to pain in the eyes, breakdown of the outer surface or cornea of the eyes, and eventual blindness. Untreated, repeated trachoma infections can result in a form of permanent blindness when the eyelids turn inward. The bacteria that cause the disease can be spread by both direct and indirect contact with an affected person's eyes or nose. Indirect contact includes through clothing or flies that have come into contact with an affected person's eyes or nose. Children spread the disease more often than adults. Poor sanitation, crowded living conditions, and not enough clean water and toilets also increase spread. Efforts to prevent the disease include improving access to clean water and decreasing the number of people infected by treatment with antibiotics. This may include treating, all at once, whole groups of people in whom the disease is known to be common. Washing by itself is not enough to prevent disease but may be useful with other measures. Treatment options include oral azithromycin and topical tetracycline. Azithromycin is preferred because it can be used as a single oral dose. After scarring of the eyelid has occurred, surgery may be required to correct the position of the eyelashes and prevent blindness. Globally, about 80 million people have an active infection. In some areas infections may be present in as many as 6090% of children and it more commonly affects women than men likely due to their closer contact with children. The disease is the cause of decreased vision in 2.2 million people of whom 1.2 million are completely blind. It commonly occurs in 53 countries of Africa, Asia, Central and South America with about 230 million people at risk. It results in US$8 billion of economic losses a year. It belongs to a group of diseases known as...  - Stroke is when poor blood flow to the brain results in cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. They result in part of the brain not functioning properly. Signs and symptoms of a stroke may include an inability to move or feel on one side of the body, problems understanding or speaking, feeling like the world is spinning, or loss of vision to one side. Signs and symptoms often appear soon after the stroke has occurred. If symptoms last less than one or two hours it is known as a transient ischemic attack (TIA) or mini-stroke. A hemorrhagic stroke may also be associated with a severe headache. The symptoms of a stroke can be permanent. Long-term complications may include pneumonia or loss of bladder control. The main risk factor for stroke is high blood pressure. Other risk factors include tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, previous TIA, and atrial fibrillation. An ischemic stroke is typically caused by blockage of a blood vessel, though there are also less common causes. A hemorrhagic stroke is caused by either bleeding directly into the brain or into the space between the brain's membranes. Bleeding may occur due to a ruptured brain aneurysm. Diagnosis is typically with medical imaging such as a CT scan or magnetic resonance imaging (MRI) scan along with a physical exam. Other tests such as an electrocardiogram (ECG) and blood tests are done to determine risk factors and rule out other possible causes. Low blood sugar may cause similar symptoms. Prevention includes decreasing risk factors, as well as possibly aspirin, statins, surgery to open up the arteries to the brain in those with problematic narrowing, and warfarin in those with atrial fibrillation. A stroke or TIA often requires emergency care. An ischemic stroke, if detected within three to four and half hours, may be treatable with a medication that can break down the clot. Aspirin should be used. Some hemorrhagic strokes benefit from...  - In ophthalmology, high-energy visible light (HEV light) is high-frequency, high-energy light in the violet/blue band from 400 to 500 nm in the visible spectrum. HEV light has been suggested as a cause of age-related macular degeneration. Some sunglasses are now designed specifically to block HEV.    Given the information, choose the subject and object entities that have the relation of 'medical specialty'.
A:
cataract , ophthalmology