Andrew A. Dahl, MD, is a board-certified ophthalmologist. Dr. Dahl's educational background includes a BA with Honors and Distinction from Wesleyan University, Middletown, CT, and an MD from Cornell University, where he was selected for Alpha Omega Alpha, the national medical honor society. He had an internal medical internship at the New York Hospital/Cornell Medical Center.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
Blindness is defined as the state of being sightless. A blind individual is
unable to see. In a strict sense the word blindness denotes the condition of
total blackness of vision with the inability of a person to distinguish darkness
from bright light in either eye. The terms blind and blindness have been
modified in our society to include a wide range of visual impairment. Blindness
is frequently used today to describe severe visual decline in one or both eyes
with maintenance of some residual vision.
Vision impairment, or low vision, means that even with eyeglasses, contact
lenses, medicine or surgery, you don't see well. Vision impairment can range
from mild to severe. Worldwide, between 300 million and 400 million people are
visually impaired due to various causes. Of this group, approximately 50 million
people are totally blind. Approximately 80% of blindness occurs in people over 50 years old
What are the different types of blindness?
Color blindness is the inability to perceive differences between some of the
colors that others can distinguish. It is most often inherited (genetic) and
affects about 8 % of males and under 1% of women. People who are color blind
usually have normal vision otherwise and can function well visually. This is
actually not true blindness.
Night blindness is a difficulty in seeing under situations of decreased
illumination. It can be genetic or acquired. The majority of people who have
night vision difficulties function well under normal lighting conditions. This
is not a state of sightlessness.
Snow blindness is loss of vision after exposure of the eyes to large amounts
of ultraviolet light. Snow blindness is usually temporary and is due to swelling
of cells of the corneal surface. Even in the most severe of cases of snow blindness, the individual is still able to see shapes and movement.
People often say, "I am 'blind as a bat' without my glasses." All bat species
have eyes, and most have excellent vision. More importantly, the term blindness
means the inability to see despite wearing glasses. Anyone who has access to
glasses and sees well with the glasses cannot be termed blind.
A stroke results from impaired oxygen delivery to brain cells via the bloodstream. A stroke is also referred to as a CVA, or cerebrovascular incident. Symptoms of stroke include: sudden numbness or weakness of the face, arm or leg. Sudden confusion, trouble speaking or understanding. Sudden trouble seeing in one or both eyes, sudden trouble walking, dizziness, or loss of balance, and/or sudden severe headache with no known cause. A TIA, or transient ischemic attack is a short-lived temporary impairment of the brain caused by loss of blood supply. Stroke is a medical emergency.
Glaucoma is a common eye condition in which the fluid pressure inside the eye rises because of slowed fluid drainage from the eye. If untreated, glaucoma may damage the optic nerve and other parts of the eye, causing the loss of vision or even blindness.
Paget's disease is a chronic bone disorder due to irregular breakdown and formation of bone tissue. Symptoms of Paget's disease include bone pain, headaches and hearing loss, pressure on nerves, increased head size, hip pain, and damage to cartilage of joints.
Leprosy (Hansen's disease) is a disfiguring disease caused by infection with Mycobacterium leprae bacteria. The disease is spread from person to person through nasal secretions or droplets. Symptoms and signs of leprosy include numbness, loss of temperature sensation, painless ulcers, eye damage, loss of digits, and facial disfigurement. Leprosy is treated with antibiotics and the dosage and length of time of administration depends upon which form of leprosy the patient has.
A cataract is an eye disease that causes the eye's lens to become cloudy and opaque with decreased vision. Causes of cataracts include diabetes, hypothyroidism, certain genetic illnesses, hyperparathyroidism, atopic dermatitis, and certain medications. Symptoms and signs include a decrease in vision and a whitish color to the affected eye. Treatment depends upon the patient's specific visual needs and may involve cataract surgery.
Many common eye disorders resolve without treatment and some may be managed with over-the-counter (OTC) products. It's important to visit a physician or ophthalmologist is the problem involves the eyeball itself or the condition hasn't improved after 72 hours of use of an eye-care OTC product.
A corneal ulcer is an open sore on the cornea. Infection is a common cause of corneal ulcer. Symptoms and signs of corneal ulcer include redness, eye pain and discharge, blurred vision, photophobia, and a gray or white spot on the cornea. Treatment depends upon the cause of the corneal ulcer.
Rocky Mountain spotted fever (RMSF) is an infectious disease that's transmitted by the bite of a tick infected with the Rickettsia rickettsii bacterial organism. Initial symptoms of RMSF include fever, nausea, vomiting, muscle pain and severe headache. Later symptoms include rash, abdominal pain, joint pain, and diarrhea. Treatment usually involves a tetracycline antibiotic.
Retinitis pigmentosa (RP) is a genetic condition that causes retinal degeneration and eventual vision loss. Symptoms include night blindness and tunnel vision. Visual field testing and electrophysiological testing are essential in diagnosing RP. Though there is no cure for RP, vitamin A therapy and an omega-3-rich diet may be recommended for patients to slow disease progression.
Scleritis is inflammation of the white part of the eye. It may be caused by a serious underlying condition, such as an autoimmune disease. Symptoms include redness, pain, tearing, sensitivity to light, and decreased visual acuity. Treatment may include eye drops as well as treatment for any underlying disease process. Scleritis cannot be prevented.
Diabetes and eye problems are generally caused by high blood sugar levels over an extended period of time. Types of eye problems in a person with diabetes include glaucoma, cataracts, and retinopathy. Examples of symptoms include blurred vision, headaches, eye aches, pain, halos around lights, loss of vision, watering eyes. Treatment for eye problems in people with diabetes depend on the type of eye problem. Prevention of eye problems include reducing blood pressure, cholesterol levels, quitting smoking, and maintaining proper blood glucose levels.
Mucormycosis (zygomycosis) is a fungal infection caused by Zygomycetes. Symptoms and signs include fever, headache, coughing, shortness of breath, abdominal pain, bloody vomit, and possible altered mental status. Treatment usually involves debridement of infected tissue and antifungal drugs.
Age-related macular degeneration (AMD) is a disease that gradually destroys the central vision. In people over 60, AMD is a leading cause of vision loss. Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula, leaking blood and fluid and causing rapid vision loss. In dry AMD, light-sensitive cells slowly break down in the macula, resulting in gradual vision loss. Pain is not associated with either form of AMD.
Color blindness is a condition where a person does not see colors in the usual way. Color blindness is a genetic condition that affects 1 out of every 10 men to some degree. Colorblindness rarely occurs in women. The condition cannot be treated or corrected.
Neuromyelitis optica (Devic's syndrome) is a disease of the CNS that affects the optic nerves and spinal cord. People with neuromyelitis optica develop optic neuritis and transverse myelitis. There is no cure for neuromyelitis optica; however, there are therapies to treat attacks when they occur.
eye. Read about symptoms, signs, diagnosis, treatment, and prognosis.
Coats' disease is a rare eye condition that typically progresses to vision loss or blindness in one eye. Gradual vision loss is usually the first symptom, followed by a cloudy white or yellow pupil due to the presence of a cataract. Treatment focuses on limiting the blood vessel progression and may involve cryotherapy or laser photocoagulation.
Smallpox is a disease caused by the variola virus. Symptoms and signs include a characteristic rash and high fever. Treatment focuses on supporting the patient. Smallpox may be prevented with the ACAM2000 smallpox vaccine.
Nonprescription eyeglasses are available over the counter (OTC) and are typically used by people who can no longer read fine print. OTC trifocals are helpful for those who require multiple distances or focal lengths for near and intermediate tasks. OTC sunglasses should offer 100% protection from the sun's UVA and UVB rays. OTC magnifying glasses are useful for viewing tiny objects or fine print.
Contact lenses fit over the cornea and correct vision problems such as nearsightedness, farsightedness, or astigmatism. Contact lenses may be hard or soft. Bifocal contact lenses may be worn by those who have presbyopia. Toric contact lenses are for people who have astigmatism.
Trachoma is an infectious disease caused by the Chlamydia trachomatis bacteria. Symptoms and signs include redness and irritation of the eyes with tearing. Trachoma is diagnosed by examining the eyes and eyelids. Treatment involves a single dose of azithromycin (Zithromax) or the use of topical tetracycline (Achromycin) ointment. Infected individuals should be counseled about sanitation and taught simple cleanliness.
Smallpox is an infectious disease of the past that was
eliminated by vaccination. The disease was caused by the variola virus, which
spread from person to person. Affected people became very ill with a high fever
and a characteristic rash. Up to one-third of people with smallpox died.
Although the disease has been wiped out, samples of the virus still exist in
high-security laboratories in the United States and Russia. This has led to
concerns about use of the virus in biological warfare. For this reason, some
military personnel are still vaccinated against smallpox.
What is the history of smallpox?
Smallpox is thought to have existed for more
than 12,000 years. Evidence of infection can be found in mummies from ancient
Egypt, including the mummy of Ramses V. Smallpox entered the New World in the
16th century, carried by European explorers and conquistadors. Because the
aboriginal inhabitant...
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