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| This glossary contains: 19186 medical terms |
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PRK
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PRK PRK stands for Photo Refractive Keratectomy which is a form of refractive surgery to correct a refractive error such as myopia. A laser is used to remove a front layer of cells of the cornea to change the refractive state of the eye so that glasses are no longer needed. Complications include under or over correction of the refractive error and glare problems, particularly at night with oncoming head lights. If serious infection occurs, blindness might result.
RELATED TERMS--------------------------------------
Surgery
Treating diseases or other medical conditions by operating on a patient to remove or repair parts of the body.
Myopia
Also known as nearsightedness, myopia is a refractive error caused by an eyeball that is too long to focus light on the retina or a cornea which is too steeply curved. In these cases light focuses instead in front of the retina. People with myopia are usually able to see close objects well, but objects in the distance—such as highway signs or writing on a chalkboard—appear blurred.
Laser
An acronym of light amplification by stimulated emission of radiation. A surgical tool that creates intense heat and power when focused at close range, destroying cells by vaporizing them.
Cornea
The front part of the eye that acts as a window for the entrance of light rays. It is attached to the other outer coat of the eye, the sclera; the white part of the eye. The cornea provides a significant amount of focusing power for the eye (the rest is provided by the lens). Because it has many nerve fibers, an injury or foreign body causes significant pain and discomfort.
Infection
Anything that invades the body and reproduces. Infections can be bacteria, protozoa, fungi, or viruses. Bacteria and fungi are one celled creatures that cause many infections including strep throat, bladder infections, and some lung infections. Fungi cause “athlete’s foot” and thrush, an infection in the mouth. Protozoa are small organisms with many cells that can cause infections in the guts or in the lungs. Most healthy people do not get protozoal infections, but people with suppressed immune systems can. Viruses are not really organisms; they are tiny particles that can live only inside another cell. They reproduce by taking over a cell and causing that cell to make more virus particles, rather than doing what the cell is supposed to do. Viruses cause most colds and flu cases.
Blindness
Legal blindness is defined as: 1) visual acuity of 20/200 (only being able to see the big E on the eye chart) or less in the best eye even with the eyes corrected by glasses or contact lenses; or, 2) The peripheral visual field is reduced to 20 degrees of visual angle or less. Twenty degrees of visual angle is about the size of a one foot ruler held at arms length.
SIMILAR TERMS--------------------------------------
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Perphenazine
An antipsychotic substance.
Pentobarbital
A hypnotic substance.
Psychotic
In the technical sense this term refers to a groups of severe mental illness where the person has periods of loses contact with reality. In a less formal manner, it is used to refer to the condition of having lost contact with reality. The person experiences severe impairment in his/her ability to function. All areas of a person's life are usually effected. Common symptoms: Hallucinations, delusions, withdrawal, impairment of intellectual function, lose of personal care skills.
Peripheral vision
Also called "side vision". That part of vision that detects objects outside of where we are directly focusing our eyes. When we look directly at something we are using the fovea - that part of our retina where there is a high density of cone photoreceptors and thus allows for detailed vision. The fovea is part of the macula - that part of our retina with mostly cone photoreceptors and used for day time vision. Outside of the macula is what is typically referred to as peripheral vision, and peripheral vision is dominated by the rod photoreceptors. Peripheral vision is used mainly for detecting objects and in directing where we should fixate our fovea or central vision. Peripheral vision is used mostly during the night. Without peripheral vision, we would have "tunnel vision". If a person has a significant loss of peripheral vision the person would be legally blind. See legal blindness.
Photophobia
Severe discomfort to bright lights. Usually a symptom of eye disease, such as glaucoma, in an infant or retinal disease in a child or adult. Sometimes treated with dark sunglasses.
PRK
Pseudostrabismus
A child's eyes appear to be out-of-alignment, and usually one eye appears to turn in. In infants this appearance is especially noticeable when there is excessive skin on either side of the nose that covers the inner corner of each eye. As the child looks to one side, part of the eye disappears under this skin and looks crossed. This condition is common in Asian - Americans.
Pterygium
A triangular membrane with blood vessels which grows from the sclera toward the occasionally onto the cornea. It occurs more often on the nasal side of the eye. It is more common in dusty and windy climates. Surgery is often necessary.
Ptosis
A drooping of the upper eyelid. In children it is usually a congenital problem. It rarely causes amblyopia. Most children simply hold their heads back if the droop is severe. Surgery, the only treatment, is usually suggested prior to starting school when the appearance is cosmetically unacceptable.
Pupil
A circular opening in the center of the iris. The size of the pupil changes according to the amount of light present. It is small in sunlight and large in a dark room.
Paxil
Paroxetime: a selective-serotonin reuptake inhibitor commonly prescribed as an antidepressant (trade name Paxil).
RELATED TERMS--------------------------------------
Surgery
Treating diseases or other medical conditions by operating on a patient to remove or repair parts of the body.
Myopia
Also known as nearsightedness, myopia is a refractive error caused by an eyeball that is too long to focus light on the retina or a cornea which is too steeply curved. In these cases light focuses instead in front of the retina. People with myopia are usually able to see close objects well, but objects in the distance—such as highway signs or writing on a chalkboard—appear blurred.
Laser
An acronym of light amplification by stimulated emission of radiation. A surgical tool that creates intense heat and power when focused at close range, destroying cells by vaporizing them.
Cornea
The front part of the eye that acts as a window for the entrance of light rays. It is attached to the other outer coat of the eye, the sclera; the white part of the eye. The cornea provides a significant amount of focusing power for the eye (the rest is provided by the lens). Because it has many nerve fibers, an injury or foreign body causes significant pain and discomfort.
Infection
Anything that invades the body and reproduces. Infections can be bacteria, protozoa, fungi, or viruses. Bacteria and fungi are one celled creatures that cause many infections including strep throat, bladder infections, and some lung infections. Fungi cause “athlete’s foot” and thrush, an infection in the mouth. Protozoa are small organisms with many cells that can cause infections in the guts or in the lungs. Most healthy people do not get protozoal infections, but people with suppressed immune systems can. Viruses are not really organisms; they are tiny particles that can live only inside another cell. They reproduce by taking over a cell and causing that cell to make more virus particles, rather than doing what the cell is supposed to do. Viruses cause most colds and flu cases.
Blindness
Legal blindness is defined as: 1) visual acuity of 20/200 (only being able to see the big E on the eye chart) or less in the best eye even with the eyes corrected by glasses or contact lenses; or, 2) The peripheral visual field is reduced to 20 degrees of visual angle or less. Twenty degrees of visual angle is about the size of a one foot ruler held at arms length.
SIMILAR TERMS--------------------------------------
PREVIOUS AND NEXT TERMS--------------------------------------
Perphenazine
An antipsychotic substance.
Pentobarbital
A hypnotic substance.
Psychotic
In the technical sense this term refers to a groups of severe mental illness where the person has periods of loses contact with reality. In a less formal manner, it is used to refer to the condition of having lost contact with reality. The person experiences severe impairment in his/her ability to function. All areas of a person's life are usually effected. Common symptoms: Hallucinations, delusions, withdrawal, impairment of intellectual function, lose of personal care skills.
Peripheral vision
Also called "side vision". That part of vision that detects objects outside of where we are directly focusing our eyes. When we look directly at something we are using the fovea - that part of our retina where there is a high density of cone photoreceptors and thus allows for detailed vision. The fovea is part of the macula - that part of our retina with mostly cone photoreceptors and used for day time vision. Outside of the macula is what is typically referred to as peripheral vision, and peripheral vision is dominated by the rod photoreceptors. Peripheral vision is used mainly for detecting objects and in directing where we should fixate our fovea or central vision. Peripheral vision is used mostly during the night. Without peripheral vision, we would have "tunnel vision". If a person has a significant loss of peripheral vision the person would be legally blind. See legal blindness.
Photophobia
Severe discomfort to bright lights. Usually a symptom of eye disease, such as glaucoma, in an infant or retinal disease in a child or adult. Sometimes treated with dark sunglasses.
PRK
Pseudostrabismus
A child's eyes appear to be out-of-alignment, and usually one eye appears to turn in. In infants this appearance is especially noticeable when there is excessive skin on either side of the nose that covers the inner corner of each eye. As the child looks to one side, part of the eye disappears under this skin and looks crossed. This condition is common in Asian - Americans.
Pterygium
A triangular membrane with blood vessels which grows from the sclera toward the occasionally onto the cornea. It occurs more often on the nasal side of the eye. It is more common in dusty and windy climates. Surgery is often necessary.
Ptosis
A drooping of the upper eyelid. In children it is usually a congenital problem. It rarely causes amblyopia. Most children simply hold their heads back if the droop is severe. Surgery, the only treatment, is usually suggested prior to starting school when the appearance is cosmetically unacceptable.
Pupil
A circular opening in the center of the iris. The size of the pupil changes according to the amount of light present. It is small in sunlight and large in a dark room.
Paxil
Paroxetime: a selective-serotonin reuptake inhibitor commonly prescribed as an antidepressant (trade name Paxil).
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This dictionary contains 19186 terms.
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