Treatment Of Subf Oveal Choroidal Neovascularization With 810nm Diode Laser And The Laser Effects On The Retina In Rabbits

Aim:As the leading cause of severe ,irreversible vision loss , subfoveal choroidal neovascularization ( CNV ) is a major public health concern . Transpupillary thermotherapy(TTT) may stabilize subfoveal CNV. This study was to observe the beneficial effects of TTT and its effects on the retina in rabbits. Methods:Part 1 :In a retrospective study, 97 patients with FFA and ICGA defined subfoveal CNV were treated with diode laser(810nm)TTT.Laser beam sizes ranged between 1.20and 3.00mm and power settings between 150?OOmw.Treatment was given in one area for lmin,the end point being novisible change or a slight greying of the retina. Outcome wasassessed with FFA , ICGA and clinical examination and visual acuity .Part 2: Longpulse diode laser was used to produce clinically undetectable (subthreshold) or barely detectable (threshold) retinal lesions in pigmented rabbits. Tissue effects at intervals after treatment were determined in sections of retina and RPE by light and electron microscopy. Power .duration and beam spot diameter of long pulse 810nm diode laser irradiated to rabbit retina were 150mw?00mw;60s;2. Omm. (Energy density was2. 87 X 105mJ/cm2 ?5. 73X105mJ/ cm2)Part 3: Longpulse diode laser was used to produce clinically undetectable (subthreshold) or barely detectable (threshold) retinal lesions in pigmented rabbits. Duration and beam spot diameter of long pulse 810nm diode laser irradiated to rabbit retina were 60s and 2. Omm. The animals were euthanized at 12h and 24h after photocoagulation. Dot blot were used.Results:1. We followed 97 eyes of 68 patients with subfoveal CNV for a mean of 4 weeks following TTT. Among 25 AMD:5/25(20%)eyes experienced improvement;19/25(76%)eyes stabilisation of vision;1/25(4%)showed decreased. 29 central exudative chorioretinopathy eyes, 8/29(28%) experienced improvement ; 19/29 (65%) stabilisation of vision; 2/29(7%) showed decreased. 15 eyes with pathologic myopia, 12/15 (80%) stabilisation of vision; 1/15 (7%) showed decreased.2. Tissue effects of threshold are similar and resemble those in the subthresholdlesion. Under light microscope,milder changes are seen in diode laser irradiation. Photorecepter outer segments are intact. RPE is mainly involved. Transmission electron microscopy showed that the cytoplasm of RPE was cavitated with loss of apical membrane. Karyorrhexis was also seen.3. Compared with controls, significantly higher levels of PEDF were observed in rabbits retinas after irradiation from 12?4hs.Conclusion:1. TTT is effective to resolution of subfoveal CNV .2. Tissue effects of threshold are similar and resemble those in the subthresholdlesion. The 810nm diode laser mainly involved the RPE, while the ganglion cell layer remained spared. So 810nm diode laser is more suitable for macular disease.3. Upregulation of PEDF after diode laser might be one of factors in the beneficial effects of photocoagulation.