Phot Health Dictionary

Coagulation of the tissues of the retina (see EYE) by laser, for treatment of diseases of the retina such as diabetic retinopathy (see under EYE, DISORDERS OF – Retina, disorders of).... photocoagulation

Sensitivity to light. It can occur in MIGRAINE, disorders of the eye, or in MENINGITIS.... photophobia

Abnormal reaction to sunlight. The condition usually occurs as a skin rash appearing in response to light falling on the skin, and it may be caused by substances that have been eaten or applied to the skin. These are called photosensitisers and may be dyes, chemicals in soaps, or drugs. Sometimes plants act as photosensitisers – for example, buttercups and mustard. The condition may occur in some illnesses such as lupus erythematosus (see under LUPUS).... photosensitivity

A form of treatment in which deliberate exposure to a photosensitising drug and ultraviolet light bene?ts certain skin diseases, particularly PSORIASIS and T-cell LYMPHOMA. A psoralen is the photoactive agent which reacts with long-wave ultraviolet light (UVA), giving the acronym, PUVA therapy.... photochemotherapy

This comprises a photosensitising agent (one activated by light), which accumulates in malignant tissue, and a source of light that activates the photosensitiser, triggering it to generate highly reactive oxygen compounds that destroy malignant cells. One such photosensitiser is temopor?n. Photodynamic therapy is used to treat various types of malignancy; a recognised complication is photosensitivity, when a patient may suffer burns after transient exposure to sunlight. Photodynamic therapy is increasingly used and photosensitivity reactions may also become more common.... photodynamic therapy

This is a description of the ?ashing lights which are a not uncommon AURA preceding an attack of MIGRAINE.... photopsia

The method by which green plants and some bacteria produce CARBOHYDRATE from water and carbon dioxide. They use energy absorbed from the sun’s rays by a green pigment in the organism called chlorophyll. Photosynthesis is one of the earth’s fundamental biological processes. As well as converting the carbon dioxide into the essential biological compound carbohydrate, the process removes the gas from the atmosphere where, if it builds to excess, the atmospheric temperature rises, thus contributing to global warming.... photosynthesis

A surgical treatment for astigmatism, myopia, and hypermetropia, in which areas of the cornea are shaved away by laser.... photorefractive keratectomy

Treatment with light, including sunlight, ultraviolet light, blue light, or lasers. Moderate exposure to sunlight is the most basic form, and is often helpful in treating psoriasis.

PUVA combines the use of long-wave ultraviolet light with a psoralen drug, which sensitizes the skin to light. This is used to treat psoriasis and other skin diseases such as vitiligo. Psoriasis may also be treated using short-wave ultraviolet light, sometimes combined with the application of coal tar.

Visible blue light is used to treat neonatal jaundice (see jaundice, neonatal), which is due to high levels of the pigment bilirubin in the blood. In phototherapy, bilirubin is converted into a harmless substance that can be excreted. To maximize exposure, the baby is undressed and placed under the lights in an incubator to keep him warm.phrenic nerve One of the pair of main nerves supplying the diaphragm. Each phrenic nerve carries motor impulses to the diaphragm, and plays a part in controlling breathing. Injury to, or surgical cutting of, 1 of the nerves results in paralysis of 1 half of the diaphragm.... phototherapy

(American) A stylish woman Photeena, Photeana, Photiena, Photeina, Photyna... photina

Diseases of the SKIN for which sunlight is partially or wholly responsible. In su?cient dosage, short-wave ultraviolet light (UVB – see ULTRAVIOLET RAYS (UVR)) always causes ERYTHEMA. Higher doses progressively cause OEDEMA and blistering; this is acute sunburn. Graduated exposure to UVB causes pigmentation (tanning). Prolonged chronic exposure to sunlight eventually accelerates ageing of the exposed skin with LENTIGO formation and loss of COLLAGEN and elastic tissue. After decades of such exposure, epidermal DYSPLASIA and CANCER may supervene.

Drugs given orally or topically may induce phototoxic reactions of various types. Thus, TETRACYCLINES exaggerate sunburn reactions. and the diuretic FRUSEMIDE may cause blistering reactions. Psoralens induce erythema and pigmentation. AMIODARONE also induces pigmentation. (See also PHOTOCHEMOTHERAPY.)

Phytophotodermatitis is a streaky, blistering photodermatosis typically seen on the limbs of children playing in grassy meadows in summer. The phototoxic reaction is caused by psoralens in weeds.

Berlocque dermatitis is a pattern of streaky pigmentation usually seen on women’s necks, caused by a reaction to psoralens in perfumes.

Certain rare metabolic diseases may lead to photosensitisation. They include the PORPHYRIAS and PELLAGRA. Other skin diseases such as lupus erythematosus (see under LUPUS) and ROSACEA may be aggravated by light exposure. Sometimes, in the absence of any of these factors, some people spontaneously develop a sensitivity to light causing various patterns of DERMATITIS or URTICARIA. The most common pattern is ‘polymorphic light eruption’ which typically appears within a day or two of arrival at a sunny holiday destination and persists until departure. Continuously exposed areas, such as the hands and face, may be ‘hardened’ and unaffected.

Treatment Appropriate clothing and headgear, sunscreen creams and lotions are the main preventative measures.... photodermatoses

Reacting poorly to sunlight, either by skin reactivity or by forming abnormal sunlight-mediated serum metabolites... photosensitive

n. pain in the eye caused by very bright light.... photalgia

n. the use of light or lasers to destroy tissue.... photoablation

n. any of various skin diseases caused by exposure to light of varying wavelength (see photosensitivity). The facial prominences and the ‘V’ of the neck are most commonly affected, the shadow areas behind the ears and below the chin being protected. A common photodermatosis is polymorphous light eruption, which affects 10% of the population. It appears with the first sunshine of spring and abates by late summer. The photodermatoses include certain *porphyrias, notably porphyria cutanea tarda.... photodermatosis

a technique for improving the sensitivity and specificity of bladder cancer diagnosis at cystoscopy using a light-sensitive agent. This agent is instilled into the bladder, taken up by the epithelial cells, and converted into a porphyrin that accumulates only in malignant and premalignant cells. It fluoresces under light of a specific wavelength and is thus highlighted against normal bladder mucosa.... photodynamic diagnosis

n. an enlarged photographic record of an object taken through an optical or electron microscope. Compare microphotograph.... photomicrograph

an electronic device that magnifies the light emitted from a *scintillator by accelerating electrons in a high-voltage field. The resulting signal can be used to display the scintillations on a TV screen. Such devices are commonly used in *gamma cameras.... photomultiplier tube

n. inflammation of the eye due to exposure to light. It is usually caused by the damaging effect of ultraviolet light on the cornea, for example in snow blindness or when lying under a sunbed.... photophthalmia

adj. relating to or describing conditions of bright illumination. For example, photopic vision is vision in bright light, in which the *cones of the retina are responsible for visual sensation. —photopia n.... photopic

n. see photodynamic therapy.... photoradiation

n. damage to the retina of the eye caused by looking at the sun without adequate protection for the eyes. The retina may be burnt by the intense light focused on it; this affects the central part of the visual field, which may be permanently lost (sun blindness).... photoretinitis

(PVP) a technique to vaporize the prostate by means of a high-energy laser, used to relieve *lower urinary tract symptoms due to benign prostatic hyperplasia (see prostate gland). It is associated with less blood loss and a shorter hospital stay than a traditional TURP (see resection), but can only be used on smaller prostates.... photoselective vaporization of the prostate

n. movement of a cell or organism in response to a stimulus of light.... phototaxis

see keratectomy.... phototherapeutic keratectomy

n. damage caused by prolonged exposure to light; for example, retinal phototoxicity is damage to the retina of the eye as a result of prolonged exposure to light.... phototoxicity

n. the excretion of phosphorescent urine, which glows in the dark, due to the presence of certain phosphorus-containing compounds derived from phosphates.... photuria

see SPECT scanning.... single photon emission computed tomography