Purpose: To analyze the occurrence of near infrared (NIR) fluorescence in relation to NIR reflectance, blue-light-excited autofluorescence, angiograms, and funduscopy.
Methods: Observational consecutive case series in patients with macular diseases. Imaging was performed with a confocal scanning laser ophthalmoscope for NIR reflectance, blue-light-excited autofluorescence, NIR fluorescence, and fluorescein and indocyanine green (ICG) angiograms. In cases in which NIR fluorescence was observed, five to nine images were averaged. The leakage of the scanning laser ophthalmoscope was analyzed.
Results: In the 291 eyes analyzed, NIR fluorescence was observed in 51 and was graded weak in 27 with wet age-related macular degeneration (AMD, 10 cases), dry AMD with pigment clumping (n=7), chronic central serous choroidopathy (CSC; n=5), choroidal nevi (n=2), subretinal hemorrhages (n=2), and chloroquine maculopathy (n=1). Strong NIR fluorescence was found in 24 eyes, with wet AMD (n=14), subretinal hemorrhages (n=8), and choroidal nevi (n=2). Except for four eyes, we observed a strong correlation of NIR fluorescence and increased NIR reflectance at identical fundus location (92.2%). NIR fluorescence corresponded with increased blue-light-excited autofluorescence in 21 of 31 patients with AMD and in 4 of 5 patients with chronic CSC, but in none of the 4 patients with nevi. Funduscopy showed that structures with NIR fluorescence were pigmented or consisted of degraded blood. Barrier filter leakage of the imaging system was 6.2x10(-6).
Conclusions: The high correlation of NIR fluorescence and reflectance indicated that part of the observed NIR fluorescence is pseudofluorescence, whereas gray-scale analysis indicated that both NIR autofluorescence and pseudofluorescence contribute to the NIR fluorescence images. Quantification of leakage of the imaging system indicated a significant part of the observed NIR fluorescence is NIR autofluorescence. As NIR fluorescence derives from pigmented lesions, melanin is a possible source if NIR reflectance is also increased. Comparison with blue-light-excited autofluorescence showed differences between AMD and patients with nevi. NIR autofluorescence was also detected in single cases of maculopathy without corresponding NIR reflectance.