photodynamic therapy

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photodynamic therapy (PDT),

a laser-assisted surgical procedure (for example, to correct age-related macular degeneration) during which a photosensitizer is activated by exposure to light to produce photochemical effects in the target area of the eye requiring care.

photodynamic therapy

A type of phototherapy in which a nontoxic light-sensitive compound that has been injected into a patient is exposed selectively to light, whereupon it becomes toxic to targeted malignant and other diseased cells.


Mainstream medicine
Bright light therapy, see there.

Experimental oncology
A therapy in which various conditions (colorectal cancer, cutaneous T-cell lymphoma, head and neck cancer, Kaposi sarcoma, psoriasis, skin cancer) are treated by light after previous administration of the agent haemoporphyrin.

photodynamic therapy

Oncology The injection of a site-specific photosensitizer in the body which accumulates in rapidly dividing cells, activated by certain wavelengths of light to treat and diagnose CA–eg, in situ transitional cell CA of bladder and other proliferative disorders. See Phototherapy Ophthalmology A nonthermal process for ↑ local reactive O2 species which mediate local cellular, vascular, and immunologic injury; RT is used for outpatient treatment of macular degeneration–characterized by choroidal neovascularization of retina. See Age-related macular degeneration.

pho·to·dy·nam·ic ther·a·py

(PDT) (fō'tō-dī-nam'ik thār'ă-pē)
A surgical laser-assisted procedure to correct wet macular degeneration; excitable dye is injected into the venous system and a laser is used to treat those ocular areas that are found to be leaking dye.

photodynamic therapy

A treatment in which a photosensitizing drug is given intravenously, followed by a local targeted irradiation by light. The method is being used effectively with laser light in selected cases of age-related macular degeneration.

Photodynamic therapy

A novel mode of treatment that uses a combination of special light rays and drugs are used to destroy the cancerous cells. First, the drugs, which make cancerous cells more susceptible to the light rays, are introduced into the bladder. Then the light is shone on the bladder to kill the cells.
Mentioned in: Bladder Cancer

macular degeneration, age-related (ARMD, AMD)

A common, chronic degenerative condition found in a large percentage of elderly patients (and sometimes middle-aged ones) characterized by loss of central vision. There are two main forms of the condition: non-neovascular (dry, atrophic) AMD, which is the most common, and exudative (wet, neovascular) AMD in which the loss of vision is the most severe. The main features of dry AMD are the presence in the macular region of small, yellowish-white spots (hard drusen) and large, poorly defined, coalescing soft drusen, focal hyperpigmentation of the retinal pigment epithelium (RPE) and at a later stage geographic atrophy of the RPE and depigmentation exposing choroidal vessels. Visual acuity becomes markedly reduced, there is metamorphopsia and the condition usually becomes bilateral over several years. The condition is managed essentially by the use of low vision aids.Exudative AMD has a similar clinical picture initially but is followed by choroidal neovascularization (CNV), which gives rise to subretinal fluid, haemorrhages, exudation, RPE detachment and subretinal fibrosis in the macular region resulting in severe loss of central vision. If detected early (usually with an Amsler chart), treatment with laser photocoagulation will reduce the risk of further visual loss. Photodynamic therapy (PDT) is another method of reducing the risk of visual loss. It allows selective destruction of the choroidal neovascularization with minimal damage to the overlying retinal tissue. It consists of injecting a photosensitizing agent (e.g. verteporfin) that is taken up by the abnormal vessels and when activated by a laser light of a given wavelength (e.g. 689 nm) it damages and shrivels up the vessels. Recent drug therapies, such as the anti-VEGF ranibizumab and bevacizumab, which are injected intravitreally at regular intervals and designed to stop the leakage and the growth of blood vessels, not only reduce loss of vision but improve visual acuity in a significant percentage of cases of wet AMD. Syn. senile macular degeneration. See fluorescein angiography; disciform scar; drusen; macular dystrophy; lipofuscin; age-related maculopathy; oxidative stress; macular pigment; Kollner's rule; photostress test; VEGF.