| Objective Transpupillary thermotherapy (TTT) is a technique in which infrared light is delivered to the choroids and the retinal pigment epithelial (RPE) through the pupil. It has been reported to be effective on the small retinal and choroidal tumors, especially lying macular area and peripapillary. Recently it has been induced to treat the choroidal neovascularization (CNV). CNV can appear in lots of chorioretinal diseases, including age-related macular degeneration (AMD), pathologic myopia (PM)?central exudative chorioretinopathy (CEC), angoid streaks, choroidal injury and choroidal tumor. Among these diseases AMD is the most common. CNV secondary to AMD is the leading cause of irreversible blindness among the elderly in industrialized countries. But one problem that has been noted with TTT is its inability to be titrated. This stems primarily from our inability to adequately monitor the temperature of the surrounding retina as the CNV is being treated because of the absence of noninvasive monitoring devices. An ophthalmoscopic end point is invisible, or just barely visible. So the therapeutic effects are not steady and the key to therapeutic effects is how to select the appropriate power. Moreover, the mechanisms and parameters of TTT treating CNV come from TTT treating tumors. In order to improve the therapeutic effects of TTT, we should undertake further experimental and clinical studies. The aim of this study is to evaluate the factors influencing effectiveness of TTT by animal experimentsand the effectiveness of TTT for the treatment of CNV by clinical observation, thus help physician select the appropriate parameters when they perform TTTMethods This study was divided into two parts.1 Animal experiments: 8 white rabbits and 20 pigmented rabbits were divided into 4 groups and TTT was performed.1.1 The threshold power of normal pigmented rabbits and white rabbits: TTT was delivered to the fundus of 6 pigmented rabbits and 6 white rabbits with fixed spot size 1.2mm and exposure time of 60 seconds with a handheld contact lens. The power varied from 800~1800mW for white rabbits and 80~180mW for pigmented rabbits to get invisible or visible burns. According to the outcome, the threshold powers of normal white rabbits and pigmented rabbits were decided.1.2 The histological changes induced by TTT with different power: TTT was delivered to the fundus of 2 white rabbits and 2 pigmented rabbits with fixed spot size 1.2mm and exposure time of 60 seconds. The powers were 1000mW (subthreshold), 1200mW (threshold), 1400mW (surperthreshold ) for white rabbits and 100mW (subthreshold), HOmW (threshold), 140mW (surperthreshold ) for pigmented rabbits respectively. Eyes were enucleated at 7 and 28 days after treatment, fixed in acid formalin and embedded in paraffin. Histological examination by light microscopy was performed on hematoxylin-eosin (HE) stained paraffin embedded sections.1.3 The histological changes induced by TTT with different choroidal circulation: TTT was delivered to the fundus of 4 pigmented rabbits with fixed spot size 1.2mm and exposure time of 60 seconds. When TTT was performed to the right eye, the right eye was pressurized by handhold contact lens to decrease the choroidal blood flow. The left eye was not pressurized and used as the control. The powers were 100mW (subthreshold), 110mW (threshold) and 140mW (surperthreshold )respectively. Eyes were enucleated at 7 and 28 days after treatment, the histological changes were observed similar to the second group.1.4 The histological changes induced by TTT with low power irradiation early: TTT was delivered to the right fundus of 8 pigmented rabbits with fixed spot size 3.0mm, exposure time of 60 seconds and power of 250mW. 24 hours later, TTT was performed to the double eyes again with fixed spot size 1.2mm and exposure time of 60 seconds. The powers were 100mW (subthreshold), 110mW (threshold) and 140mW (surperthreshold ) respectively. Eyes were enucleated at 7 and 28 days after treatment, th...
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