Medications

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 them; to diagnose...

Pagetic - Medical

Pagetic: Pertaining to Paget disease, a chronic disorder that typically results in enlarged, deformed bones due to excessive breakdown and formation of bone tissue that can cause bones to weaken and may result in bone pain, arthritis, bony deformitie...

Optician - Medical

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.Last Editorial Review: 4/27/...

Paget disease of the breast - Medical

Paget disease of the breast: The combination of scaly skin changes of the nipple resembling eczema and an underlying cancer of the breast. The nipple is inflamed because of the presence of Paget's cells. These large irregular cells are themselves no...

Optic neuroma - Medical

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 treated by surgical ex...

Optic nerve pathways - Medical

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 cr...

Paget disease - Medical

Paget disease: A chronic bone disorder that typically results in enlarged, deformed bones due to excessive breakdown and formation of bone tissue that can cause bones to weaken and may result in bone pain, arthritis, deformities or fractures. The dis...

Optic nerve head - Medical

Optic nerve head: The circular area in the back of the inside of the eye where the optic nerve connects to the retina.Last Editorial Review: 9/26/1999 8:46:00 PM...

Optic nerve - Medical

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 dispatched through...

Page kidney - Medical

Page kidney: Chronic longstanding compression of the kidney resulting in hypertension. The kidney is compressed, most often, by a post-traumatic subcapsular hematoma (a collection of blood beneath the capsule surrounding the kidney) or, less often,...

Optic glioma - Medical

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 and by destructi...

Paediatrics - Medical

Paediatrics: Pediatrics in Great Britain. Last Editorial Review: 3/26/1998 2:27:00 PM...

Optic disc - Medical

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.Last Editorial Review: 9/26/1999 8:45:00 PM...

PAD - Medical

PAD: Peripheral artery disease.Last Editorial Review: 2/8/2004 Peripheral artery disease: A form of peripheral vascular disease in which there is partial or total blockage of an artery, usually one leading to a leg or arm. Leg artery disease and arm...

Optic cup - Medical

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. Last Editorial Review: 9/26/1999 8:42:00 PM...

Optic - Medical

Optic: Having to do with vision. Last Editorial Review: 4/27/2011 5:27:15 PM...

Pacing, diaphragm - Medical

Pacing, diaphragm: See: Diaphragm pacing.Last Editorial Review: 3/15/2003Diaphragm pacing: A procedure to help patients with spinal cord injuries to breathe. Their breathing is helped by setting the respiratory rate by electrical stimulation (pacing)...

Pacifier - Medical

Pacifier: An artificial nipple, usually made of plastic, upon which an infant can suck to gain some solace and quiet down. A pacifier is called by other names in other countries including a "dummy" in the U.K. Pacifiers have been claimed to caus...

Opportunistic microorganism - Medical

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 bod...

Opportunistic infection - Medical

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 o...

Opportunistic condition - Medical

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 ma...

Pachyonychia - Medical

Pachyonychia : Elephant nail, a fingernail or toenail that is abnormally thick. From the Greek pachys, thick + onyx, nail = thick nail. Last Editorial Review: 5/10/2002...

Opium - Medical

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 centuries, opium was ...

Pachymeninx - Medical

Pachymeninx: The dura. From pachy- (thick) + -meninx ( membrane). The plural is pachymeninges.Last Editorial Review: 5/10/2004 Dura: The outermost, toughest, and most fibrous of the three membranes ( meninges) covering the brain and the spinal cord....

Pachymeninges - Medical

Pachymeninges: The dura. From pachy- (thick) + -meninges ( membranes). The singular is pachymeninx.Last Editorial Review: 5/10/2004 Dura: The outermost, toughest, and most fibrous of the three membranes ( meninges) covering the brain and the spinal ...

Opisthotonos - Medical

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 cord. It also occ...

Opioid - Medical

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. Last Editorial Review: 4/27/2011 5:27:15 PM...

Pachydermatous - Medical

Pachydermatous: 1. Thick-skinned like a pachyderm (an elephant, rhinoceros, or hippopotamus). 2. By extension, insensitive.Last Editorial Review: 5/30/2004...

Opiate agonist maintenance - Medical

Opiate agonist maintenance: See: Methadone treatment program. Last Editorial Review: 12/14/2003 Methadone treatment program: A program for opiate addicts, usually conducted in an outpatient setting. These programs use a long-acting synthetic opia...

Pachyderma - Medical

Pachyderma: Thick skin, like that of a pachyderm (an elephant, rhinoceros, or hippopotamus). The adjective is pachydermatous. Pachyderma can occur in several medical conditions, such as chronic lymphedema. From the Greek pachydermos meaning "thick s...