Diseases & conditions A-Z List
Diseases & Conditions A-Z List - «O»:
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Ophthalmoscopy
Ophthalmoscopy is an examination of the back part of the eyeball (fundus), which includes the retina, optic disc, choroid, and blood vessels.
How the Test is Performed
There are different types of ophthalmoscopy.
Direct ophthalmoscopy
Indirect ophthalmoscopy
Slit-lamp ophthalmoscopy
Direct ophtha...
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Opiate withdrawal
Opiate withdrawal refers to the wide range of symptoms that occur after stopping or dramatically reducing opiate drugs after heavy and prolonged use (several weeks or more).
Opiate drugs include heroin, morphine, codeine, Oxycontin, Dilaudid, methadone, and others.
Causes
About 9% of the population...
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Opioid intoxication
Opium and its forms (which include morphine, heroin, oxycodone, and the synthetic opioid narcotics) lead to an abnormal mental state, which generally involves excessive sleepiness or unconsciousness.
Causes
In the United States, the most commonly abused opioids are heroin and methadone.
Symptoms
Sy...
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Opisthotonos
Opisthotonos is a condition in which the body is held in an abnormal posture. It usually involves rigidity and severe arching of the back, with the head thrown backward. If a person with opisthotonos lays on his or her back, only the back of the head and the heels would touch the supporting surface....
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Oppositional defiant disorder
Oppositional defiant disorder is a pattern of disobedient, hostile, and defiant behavior toward authority figures.
Causes
This disorder is more common in boys than in girls. Some studies have shown that it affects 20% of school-age children. However, most experts believe this figure is high due to ...
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Optic glioma
Gliomas are tumors that grow in various parts of the brain. Optic gliomas can affect:
One or both of the optic nerves, which carry visual information to the brain from each eye
The optic chiasm, the area where the optic nerves cross each other in front of the hypothalamus of the brain
An optic gli...
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Optic nerve atrophy
Optic nerve atrophy is damage to the optic nerve. The optic nerve carries images of what we see from the eye to the brain.
Causes
There are many unrelated causes of optic atrophy. The most common cause is poor blood flow, called ischemic optic neuropathy, which most often affects elderly people. Th...
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Optic neuritis
Optic neuritis is inflammation of the optic nerve. It may cause sudden, reduced vision in the affected eye.
Causes
The cause of optic neuritis is unknown.
Sudden inflammation of the nerve connecting the eye and the brain (optic nerve) can injure the insulation (myelin sheath) surrounding each nerve...
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Oral cancer
Oral cancer is cancer of the mouth.
Causes
Oral cancer most commonly involves the tissue of the lips or the tongue. It may also occur on the:
Cheek lining
Floor of the mouth
Gums (gingiva)
Roof of the mouth (palate)
Most oral cancers look very similar under the microscope and are called squam...
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Oral cholecystogram
Oral cholecystogram is an x-ray of the gallbladder, an organ in the right upper abdomen that stores bile. The x-ray is taken before the gallbladder releases bile.
How the Test is Performed
The test is done in a hospital radiology department or in the health care provider's office by an x-ray techni...
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Oral hypoglycemics overdose
Oral hypoglycemic pills are a class of prescription medications used to control diabetes. Oral means "taken by mouth." There are many different types of oral hypoglycemics. This article focuses on a class called sulfonylureas.
An overdose occurs when someone accidentally or intentionally takes more ...
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Oral mucositis
Radiation therapy or chemotherapy may cause mucositis (tissue swelling) in your mouth. You may have any of these symptoms:
Mouth pain
Mouth sores
Infection
Bleeding, if you are getting chemotherapy. Patients getting radiation therapy usually do not have bleeding.
In patients getting chemotherapy, ...
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Orbit CT scan
A computed tomography (CT) scan of the orbit is an imaging method that uses x-rays to create detailed pictures of the eye sockets (orbits) and eyes (globes).
See: CT scan
How the Test is Performed
A special dye, called contrast, may be injected into your hand or forearm before the test starts. Con...
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Orbital pseudotumor
Orbital pseudotumor is a swelling of the tissues behind the eye in an area called the orbit. The orbit is the bony cavity in the skull where the eye sits. It protects the eyeball and the muscles and tissue that surround it.
Unlike cancerous tumors, an orbital pseudotumor does not spread to other tis...
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Orchitis
Orchitis is swelling (inflammation) of one or both of the testicles.
Causes
Orchitis may be caused by an infection from many different types of bacteria and viruses. It is usually a result of epididymitis, inflammation of the tube that connects the vas deferens and the testicle.
The most common vir...
