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F. N. Reinholz, I. J. Constable, A. Riono; Verteporfin Accumulation in Experimental CNV Rats’ Retinas as Studied With an SLO. Invest. Ophthalmol. Vis. Sci. 2007;48(13):29.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the locations of drug accumulation after verteporfin injection as a possible explanation for the variability in the outcome of PDT treatments in AMD patients.
Pigmented rats underwent retinal laser photocoagulation. After two weeks the rats had developed lesions similar to those of human CNV as detected from fluorescein leakage. Fluorecein angiography was performed with a prototype SLO that includes a 50 mm focal length correction lens near the rat’s eye. A week later Visudyne® was injected into the rats’ tail veins. The prototype SLO was modified (high gain, low noise photomultiplier; separation and blocking filters at 650 nm) to allow the detection of verteporfin autofluorescence. Verteporfin angiography - displaying on-line video images - was performed using the modified SLO with the 488 nm line of an Argon ion laser for excitation.
Dual-channel angiographic images (channel 1: fluorescence, channel 2: reflection) from fluorescein and verteporfin angiography were recorded at different times. The images were registered using the reflection views as reference frames. The fluorescein (green) and verteporfin (red) angiograms were then used as different bands to form a single false colour image of the retina, see Figure 1. This allows for easy - though subjective - evaluation of the locations of the photosensitizing drug. We found that verteporfin fluorescence peaked between 20 and 30 minutes after injection. Visudyne ® pooling was observed in neovascular membranes but also in choroidal scar tissue.
An SLO can be modified to perform verteporfin angiography though the signals are weak and the images are noisy. Overlaying these images with fluorescein angiograms allows judgments on the retinal locations of verteporfin buildup. In particular, their proximity to CNV areas (as indicated by fluorescein leakage) can be investigated. It appears possible to correlate the outcome of PDT treatment with the locations of drug accumulation. In a next step we will conduct a pilot study to find out whether there are indeed statistically significant differences in drug accumulation patterns in AMD patients.
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