Photodynamic therapy
A form of treatment that uses a photosensitizing agent, administered by mouth or intravenously, which concentrates selectively in certain cells, followed by exposure of the involved tissue to a special light (such as laser or ultraviolet light), in order to destroy as much of the abnormal tissue as possible. For example, photodynamic therapy is used to treat some forms of cancer and psoriasis. Also known as photochemotherapy.
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- Photokeratitis
A burn of the cornea (the clear front surface of the eye) by ultraviolet B rays (UVB). Also called radiation keratitis or snowblindness. The condition typically occurs at high altitudes on highly reflective snow fields or, less often, with a solar eclipse. Artificial sources of UVB can also cause snowblindness. These sources include suntanning beds, […]
- Photophobia
Painful oversensitivity to light. For example, photophobia is often seen in measles and iritis. Keeping lights dim and rooms darkened is helpful when a patient has photophobia. Sunglasses may also help.
- Photorefractive keratectomy (PRK)
A kind of laser eye surgery designed to change the shape of the cornea to eliminate (or reduce) the need for glasses and contact lenses. The laser is used to remove the outer layer of the cornea and flatten the cornea. The flattening of the cornea is intended to correct myopia (nearsightedness) and astigmatism (uneven […]
- Photosensitivity
Oversensitivity of skin to light. Photosensitivity can be a side effect of medications or result from diseases, such as lupus. Treatment depends on the severity of the reaction and the cause. Photosensitivity can be prevented by avoiding skin exposure to ultraviolet light.
- Phototherapy
Treatment with light. For example, a newborn with jaundice may be put under special lights to help reduce the amount of bilirubin pigment in the skin.