Medical terms - Letter O (page 4) | MedicalVocabulary.org

Open reading frame

A long sequence of DNA that has no stop codon (no signal to stop reading) and therefore may encode part or all of a protein
Open wound

An injury that is exposed due to broken skin. An open wound is at high risk for infection
Open-angle glaucoma

Glaucoma: Glaucoma in which the aqueous (fluid) that flows through the pupil into the anterior (front) chamber of the eye cannot get through a filtration system called the trabecular meshwork into the drainage canals…
Open-label

A term used to describe the situation when both the researcher and the participant in a research study know the treatment the participant is receiving. Open-label is the opposite of double-blind when neither the…
Open-label trial

A clinical trial in which researchers and participants know which drug or vaccine is being administered
Opening, vaginal

The opening to the muscular canal extending from the cervix to the outside of the body. The word 'vagina' is a Latin word meaning 'a sheath or scabbard', a scabbard into which one might slide and sheath a sword. The…
Operating room

A facility equipped for performing surgery. Abbreviated OR
Operation

Although there are many meanings to the word 'operation', in medicine it refers to a surgical procedure. To put matters more formally, an operation is 'an act or series of acts performed upon the body with the hand…
Operation, Blalock-Taussig

A pioneering heart operation named after the American surgeon Alfred Blalock (1899-1964) and the pediatric cardiologist Helen B. Taussig (1898-1986). Dr. Taussig designed and Dr. Blalock carried out the first…
Operation, Glenn

See: Glenn shunt
Operation, Macewen

A surgical operation for inguinal hernia designed by Sir William Macewen (1848-1924), a surgeon in Glascow, Scotland who also described Macewen's sign for the detection of hydrocephalus and brain abscess.
Operon

A set of genes transcribed under the control of an operator gene. More specifically, an operon is a segment of DNA containing adjacent genes including structural genes, an operator gene, and a regulatory gene. An operon…
Ophthalmia

Inflammation of the eye. Also known as ophthalmitis
Ophthalmic

Pertaining to the eye. An ophthalmic ointment is designed for the eye.
Ophthalmic artery

The ophthalmic artery supplies blood to the eye and adjacent structures of the face. It arises from the internal carotid artery that courses up deep within the front of the neck
Ophthalmic migraine

Migraine involving the eyes but without headache. Migraine, due to a spasm of blood vessels in the brain, usually causes a headache. Flashes of light may appear as jagged lines or 'heat waves' in one or both eyes and…
Ophthalmic veins

The orbital cavity is drained by paired veins called the superior and inferior ophthalmic veins. The superior ophthalmic vein arises at the inner angle of the orbit and follows the course of the ophthalmic artery into…
Ophthalmitis

Inflammation of the eye. Also known as ophthalmia
Ophthalmologist

An eye doctor. A physician practicing ophthalmology. An ophthalmologist is an M.D.
Ophthalmology

The art and science of eye medicine.
Ophthalmopathy

Any eye disease. External ophthalmopathy may refer to any disease of the eyelid, cornea, conjunctiva, or eye muscles while internal ophthalmopathy refers to any disease in the interior of the eye. From the Greek roots…
Ophthalmoplegia with myopathy

See: Kearns-Sayre syndrome
Ophthalmoplegia with ragged-red fibers

See: Kearns-Sayre syndrome
Ophthalmoplegia-plus syndrome

See: Kearns-Sayre syndrome
Ophthalmoscope

A lighted instrument, one of the most important tools of the physician, used to examine the interior of the eye, including the lens, retina and optic nerve. The common clinical ophthalmoscope consists of a concave…
Ophthalmoscopy

Examination of the interior of the eye, including the lens, retina and optic nerve, by indirect or direct ophthalmoscopy. Indirect ophthalmoscopy employs a head lamp device to shine a very bright light into the eye…
Opiate

A medication or illegal drug that is either derived from the opium poppy, or that mimics the effect of an opiate (a synthetic opiate). Opiate drugs are narcotic sedatives that depress activity of the central nervous…
Opiate agonist maintenance

See: Methadone treatment program
Opioid

1. A synthetic narcotic that resembles the naturally occurring opiates. 2. Any substance that binds to or otherwise affects the opiate receptors on the surface of the cell
Opisthotonos

A great rigid spasm of the body with the back fully arched and the heels and head bent back. Opisthotonos occurs in meningitis, especially in infants, due to irritation of the membranes surrounding the brain and spinal…
Opium

An addictive narcotic drug derived from the unripe seedpods of the opium poppy. Preparations of opium were called laudanum. Derivatives of laudanum include paregoric (a drug to treat diarrhea), morphine and heroin. For…
Opportunistic condition

A condition that occurs especially or exclusively in persons with a weak immune system due, for example, to AIDS, cancer or immunosuppressive drugs, such as corticosteroids or chemotherapy. An opportunistic condition…
Opportunistic infection

An infection that occurs because of a weakened immune system. Opportunistic infections are a particular danger for people with AIDS. The HIV virus itself does not cause death, but the opportunistic infections that occur…
Opportunistic microorganism

A bacteria, virus, or fungus that takes advantage of certain opportunities to cause disease. Those opportunities are called opportunistic conditions. These microorganisms are often ones that can lie dormant in body…
Optic

Having to do with vision.
Optic cup

The white, cup-like area in the center of the optic disc. The optic disk is the circular area at the back of the inside of the eye where the optic nerve connects to the retina
Optic disc

The circular area in the back of the inside of the eye where the optic nerve connects to the retina. Also called the optic nerve head
Optic glioma

A benign tumor on an optic nerve or the optic chiasm (the crossing of the two optic nerves). Optic gliomas are derived from glial cells and are classified as low-grade astrocytomas. They cause symptoms both by pressure…
Optic nerve

The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are…
Optic nerve head

The circular area in the back of the inside of the eye where the optic nerve connects to the retina
Optic nerve pathways

The left and right branches of the optic nerves join behind the eyes, just in front of the pituitary gland, to form a cross-shaped structure called the optic chiasma. Within the optic chiasma, some of the nerve fibers…
Optic neuroma

A slow-growing benign tumor of the optic nerve. Optic gliomas are associated with neurofibromatosis type 1 (NF1), can lead to partial or complete loss of vision, painless bulging of the eye, and headache, and are…
Optician

A specialist in fitting eyeglasses and making lenses to correct vision problems. An optometrist performs eye examinations and writes prescriptions for corrective lenses; an optician fills that prescription
Optometrist

A health care professional who is licensed to provide primary eye care services: > >to examine and diagnose eye diseases such as glaucoma, cataracts, and retinal diseases and, in certain states in the U.S., to treat…
OPV

Oral polio vaccine. See Polio vaccine, oral
OR (abbreviation)

Stands for 'operating room'. A facility equipped for performing surgery. OR is sometimes written O.R.
Oral

Having to do with the mouth; given by mouth, as in an oral solution
Oral aversion

Reluctance or refusal to feed or eat. A familiar example of oral aversion is a baby's refusal to breastfeed. Prolonged intravenous or nasogastric feeding may also contribute to the development of oral aversion
Oral cancer

Oral cancer: Cancer within the mouth.
Oral candidiasis

Yeast infection of the mouth and throat caused by the fungus Candida albicans; also known as thrush. Yeast organisms are part of the germs normally found in various parts of the body. They ordinarily do not cause any…