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W.R. Freeman, K. Bessho, N. Rodanant, D.G. Bartsch, L. Cheng; The Effect of Subthreshold Infrared Laser Treatment for Drusen Regression on Macular Autofluorescence in Patients With Age Related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5020.
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Purpose: Subthreshold diode laser therapy has been shown to cause regression of drusen as judged by fundus photography. Using this method, visible laser burns are not created in the retina; presumably the energy is absorbed by the RPE and stimulates phagocytosis or other methods of reabsorption of drusen material, sparing photoreceptors from destruction. We hypothesized that autofluorescence changes would be visible at the level of the RPE after such treatment and that this might be sensitive to quantify RPE changes after treatment. Methods: 288 subthreshold infrared diode laser spots (48 per eye) were placed around the macula following several test burns in six patients as treatment to cause drusen regression. Prior to, immediately after and three months after treatment, color fundus photograph (CF), fluorescein angiography (FA) and autofluorescence (AF) images were analyzed. FA and AF images were obtained using a confocal SLO (Heidelberg Engineering), and frame-averaged to gain higher quality. CF was performed using a conventional fundus camera. Excluding CF-visible immediately-after laser lesions (these were defined as overthreshold treatment), presence of laser lesions was determined at all time points using overlay technique for all three imaging methods. Results: Three of six eyes showed apparent drusen reduction in CF reading at three months. AF was more sensitive than FA in half of six eyes at the immediate-after period (72% vs 16%), and in four at three months (63% vs 49%). The overall sensitivity of AF compared to FA was 47% vs 22% (p<0.0001 Chi-Square Test) at the immediate-after period and 65% vs 58% at three months period. At three months post treatment, most lesions were detectable by both imaging modalities. Conclusion: Immediately after the subthreshold diode laser treatment in the macular region, changes in autofluorescence were more sensitive to detecting RPE changes than FA. This suggests that non-invasive AF imaging may allow prediction of effect of the subthreshold diode laser on the RPE and might be used to titrate treatment dose.
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