Glossary

Health Terms beginning with "O"

Obese

Having an excessive amount of body fat.

Obesity

A chronic, metabolic disease of which the defining characteristic is excess body fat. Women are defined as obese if they are 20 percent or more over normal body weight or have a body-mass index of 30 or more.

Obsessive-compulsive disorder

A condition marked by persistent and recurring thoughts (obsessions) typically reflecting exaggerated anxiety or fears that have no basis in reality; sufferers often feel compelled to perform a ritual or routine to help relieve anxiety caused by their obsessions; they typically realize the ritual or compulsion makes no sense yet feel powerless to stop.

Obstructive sleep apnea

A serious, potentially life-threatening disorder characterized by brief interruptions of breathing during sleep caused by blocked air passages in the throat, nose or mouth.

Occipital lobe epilepsy

Epilepsy with seizures that originate in the occipital lobe of the brain. It usually begins with visual hallucinations, rapid eye blinking or other eye-related symptoms.

Occluded

Closed off or blocked, as in an occluded artery.

Occupational therapy

Rehabilitation designed to help patients improve their independence and functional ability through specific activities and exercises.

Oligomenorrhea

Infrequent menstrual periods, typically defined as eight or fewer per year.

Oligo ovulation

Maturation and discharge of fewer than normal number of eggs from the ovaries.

Oncologist

A doctor who specializes in treating cancer.

Oophorectomy

The surgical removal of one or both ovaries; used as a treatment for ovarian cancer and also as a preventive therapy for extremely high-risk patients.

Open-angle

The most common form of glaucoma, in which the angle where the cornea and the iris meet is open, but the aqueous humor fluid passes too slowly through the meshwork drain, gradually increasing eye pressure that compresses cells in the optic nerve, causing vision loss.

Open-label trial

A drug trial in which both the researchers and the volunteers know what drug is being administered and at what dose. A non-blinded or non-randomized trial.

Ophthalmoplegic migraine

In ophthalmoplegic migraine, the pain is around the eye and is associated with a droopy eyelid, double vision and other sight problems.

Ophthalmoscope

A devise used to examine the interior structures of the eye, especially the retina; it has a mirror that reflects light into the eye and a hole through which the practitioner looks.

Ophthalmoscopy

A visual examination of the optic nerve and retina through dilated pupils using a special instrument for viewing the back of the eye.

Opiate

A derivative of opium or synthetic narcotics.

Opioids

Pain-killing and relaxing drugs that can suppress restless legs syndrome.

Opportunistic infections

Illnesses caused by various organisms, most of which usually do not cause disease in people with normal immune systems. People living with advanced HIV infection may suffer opportunistic infections of the lungs, brain, eyes and other organs.

Optic nerve

A bundle of about 1.2 million nerve fibers that carry the visual images from the retina to the brain.

Oral contraceptives

Drugs taken orally that are used to prevent pregnancy.

Oral glucose tolerance test

A test to see if you have diabetes. The test is given in a lab or health care professional's office in the morning before you have eaten. A first sample of blood is taken from you. Then you drink a liquid that has glucose (sugar) in it. After one hour, a second blood sample is drawn, and, after another hour, a third sample is taken. The object is to see how well the body deals with the glucose in the blood over time.

Osteoarthritis

Also known as degenerative joint disease, it primarily affects cartilage within the joints, causing it to fray, wear, ulcerate and, in extreme cases, to wear away entirely, leaving a bone-on-bone joint. At the edges of the joint, bony spurs may form.

Osteogenesis imperfecta

An autosomal dominant disorder that impairs the body's ability to make an essential building-block protein called collagen, or produces an altered form of collagen, leading to weak bones that break easily. The most severe form, Type II, is usually fatal at a young age or even at birth. The Type III form produces bone fractures that are often present at birth, and x-rays may reveal healed fractures that occurred before birth. Because OI has a dominant pattern of inheritance, a parent with the disease has a 50 percent chance of passing it to a child. It is often caused by a new mutation in the affected individual (not inherited from a parent).

Osteopathic manipulative treatment (OMT)

Manual techniques used by doctor of osteopathy (DOs) to diagnose and correct structural and other problems.

Osteopathic medicine

A comprehensive system of medicine that emphasizes the relationship between the musculoskeletal structure and the function of the entire body.

Osteopath (or doctor of osteopathy)

A doctor of osteopathy; one who practices osteopathy (or osteopathic medicine), a system of medicine that emphasizes the relationship between the musculoskeletal structure and the function of the entire body.

Osteopenia

Low bone mass; considered a risk factor for osteoporosis, but not severe enough to be classified as osteoporosis. The bone decreases in density somewhat but is not necessarily at a higher risk for fracture.

Osteoporosis

A preventable and treatable disease that thins and weakens your bones, making them fragile and more likely to break. It is sometimes called a "silent disease," because it can occur gradually over many years without your knowledge. Often the first symptom of osteoporosis is a broken bone

Ostial obstruction

A blockage of the sinus openings; often a culprit in chronic sinusitis.

Ovarian cancer

Cells of the ovary grow and divide uncontrollably. Cells may grow to form a tumor on the ovary and can break off from the main tumor and spread to other parts of the body. Although ovarian cancer can spread throughout the entire body, in most cases it stays in the abdomen and affects organs such as the intestines, liver and stomach.

Ovaries

The pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are in the lower abdomen, one on each side of the uterus. These 1 ½ inch-long, walnut-shaped organs release hormones that help control the menstrual cycle.

Ovary

One of a pair of female reproductive glands in which the ova, or eggs, are formed. The ovaries are in the lower abdomen, one on each side of the uterus. These 1 ½ inch long, walnut-shaped organs release hormones that help control the menstrual cycle.

Overactive bladder

A bladder that contracts involuntarily, causing urge incontinence.

Overflow incontinence

A type of incontinence in which the bladder remains full and leaks urine. You may feel as though you need to empty your bladder but cannot, or you may urinate a small amount but feel like your bladder is still full.

Over-the-counter

Medications sold lawfully without a prescription.

Ovulation

The monthly release of an egg from an ovary. This usually happens 14 days before the beginning of your period (menstrual flow). When the egg is released, it travels through the fallopian tube, where it could become fertilized by a sperm. If it is fertilized, it attaches to the wall of the uterus (womb) for development and growth. If it's not fertilized, the egg passes out of the body with the menstrual flow.

Ovulation phase

The brief mid-cycle (day 14) stage during which the egg is released by the ovary and migrates into the fallopian tube, where it awaits fertilization.

Oxalate

A chemical that combines with calcium in urine to form the most common type of kidney stone (calcium oxalate stone).

Oxybutynin

A medication (brand names Ditropan or Oxytrol) for bladder control problems. It blocks bladder muscle contractions and is recommended for treatment of urge incontinence.