Applications of Transpupillary Thermotherapy In Different Posterior Segment Disorders
Omnia Mahmoud Asaad Sherif;
Abstract
Hyperthermia is the elevation of temperature above the normal body temperature of 37°C and it has long been recognized as a useful treatment for human neoplasms. As regard the eye, thermotherapy has been applied for the treatment of intraocular tumors. Several thermotherapy sources have been used, including ultrasound, microwaves, localized current field and ferromagnetic thermoseeds in which heat is delivered in a transscleral fashion. Direct transpupillary thermotherapy using infrared radiation is used to avoid aberrations of transscleral thermotherapy.
Transpupillary thermotherapy (TTT) is a low irradiance, large spot size, prolonged exposure (Long-Pulse), infrared laser photocoagulation protocol. The low temperature, long-pulse photocoagulation is a potential strategy for decreasing neural retinal damage. Infrared diode laser with 810nm wavelength is currently used.
The objective is to cause tumor cell death by raising the temperature between 45°C and 60°C for about one minute. Diode laser applications, 3.0mm in diameter, are placed over the entire tumor surface. Each exposure is about 60 seconds long, with the power adjusted so that the treated area develop a light gray appearance at the end of each application. About 1.5-2.0mm of clinically normal choroid around the tumor is treated to prevent marginal recurrence. Histological studies suggest that a single treatment causes tumor necrosis to a depth of 3-
4mm, and this is believed to occur because the tumor blood vessels remain patent, transferring heat to the deeper part of the tumor.
The combined effect of hyperthermia when added to radiation therapy, is more than additive. Hyperthermia potentiates radiation therapy as heat renders cellular enzymes used to repair sublethal radiation damage ineffective, heat can directly kill cells and it also cause vascular damage.
TTT is applied for the treatment of choroidal melanomas, retinoblastoma, circumscribed choroidal hemangiomas, capillary papillary hemangioma and recently choroidal metastasis. It has also been used for the treatment of choroidal neovascularization secondary to age related macular degeneration.
Transpupillary thermotherapy (TTT) is a low irradiance, large spot size, prolonged exposure (Long-Pulse), infrared laser photocoagulation protocol. The low temperature, long-pulse photocoagulation is a potential strategy for decreasing neural retinal damage. Infrared diode laser with 810nm wavelength is currently used.
The objective is to cause tumor cell death by raising the temperature between 45°C and 60°C for about one minute. Diode laser applications, 3.0mm in diameter, are placed over the entire tumor surface. Each exposure is about 60 seconds long, with the power adjusted so that the treated area develop a light gray appearance at the end of each application. About 1.5-2.0mm of clinically normal choroid around the tumor is treated to prevent marginal recurrence. Histological studies suggest that a single treatment causes tumor necrosis to a depth of 3-
4mm, and this is believed to occur because the tumor blood vessels remain patent, transferring heat to the deeper part of the tumor.
The combined effect of hyperthermia when added to radiation therapy, is more than additive. Hyperthermia potentiates radiation therapy as heat renders cellular enzymes used to repair sublethal radiation damage ineffective, heat can directly kill cells and it also cause vascular damage.
TTT is applied for the treatment of choroidal melanomas, retinoblastoma, circumscribed choroidal hemangiomas, capillary papillary hemangioma and recently choroidal metastasis. It has also been used for the treatment of choroidal neovascularization secondary to age related macular degeneration.
Other data
| Title | Applications of Transpupillary Thermotherapy In Different Posterior Segment Disorders | Other Titles | تطبيقات العلاج الحراري عبر الحدقة في الإعتلالات المختلفة للجزء الخلفي من للعين | Authors | Omnia Mahmoud Asaad Sherif | Issue Date | 2002 |
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