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K. Bessho, D.–U.G. Bartsch, H.–J. Koh, I. Kozak, W.R. Freeman; Characteristics of autofluorescence and optical coherence tomography imaging after prophylactic subthreshold diode laser treatment for drusen . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2204.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Subthreshold laser treatment affects the retinal pigment epithelium and secondarily causes re–absorption of drusen. It has also been suggested as a minimally invasive treatment for diabetic macular edema. Previously, we have shown that confocal scanning laser ophthalmoscopic (cSLO) autofluorescence imaging (AF) immediately after treatment detects 29.6% of applied subthreshold lesions those were opthalmoscopically invisible. We wished to study the appearance of these lesions by Optical Coherence Tomography (OCT). Methods: 12 eyes of 11 patients with dry type age–related macular degeneration underwent subthreshold diode laser (810nm) treatment to cause drusen regression. Prior to and immediately post treatment, conventional color fundus photography (CF), confocal fundus autofluorescence imaging (AF) using the Heidelberg Retina Angiograph (HRA, Heidelberg Engineering, Vista, CA) and third generation OCT (Stratus OCT, Carl Zeiss Meditec, Dublin CA) using a custom tight scan pattern were performed. Digital image overlays allowed analysis of OCT scans that transected known AF and CF changes. Results: Immediately post treatment, 29.1% of AF–detectable subthreshold laser lesions which were OCT transected were detected by OCT. OCT detected 60.4% of suprathreshold treatment lesions shown in CF. OCT–detectable changes were characterized as increased reflectivity in the outer retina and decreased reflectance in the presumed RPE band. OCT detected 8.5% of the total lesions which were not seen by AF or CF presumably detecting AF undetected subthreshold lesions. Conclusions: Fundus autofluorescence imaging is more sensitive than OCT in detecting the effect of subthreshold diode laser on the RPE and outer retina. Using current OCT technique there are gaps between scan lines, which prevent complete sampling of any given retinal area. The OCT characteristics of subthreshold RPE lesions may allow insight into the physiology of drusen resorption. The patho–anatomic nature of the subthreshold lesion remains unknown.
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