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E. F. van Kuijk, B. Bell, R. Johnston, M. Motamedi; Assesment of Laser Tissues Interaction Using Fundus Autofluorescence. Invest. Ophthalmol. Vis. Sci. 2007;48(13):141. doi: https://doi.org/.
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Fundus autofluorescence is now more widely being used for phenotyping of inherited retinal disease. Fluorescence imaging may provide a highly sensitive method for non-invasive quantitative assessment of laser-induced lesions in the retina by monitoring of changes in autofluorescence of fluorophores in the retinal pigment epithelium (RPE) following laser irradiation.as function of exposure parameters
Retired female breeding stock Brown-Norway rats were purchased at an approximate age of 6 months. A modified Heidelberg Retina Angiograph (HRA I) was used to obtain images of the fundus by either infra red (IR) reflectance or autofluorescence using excitation wavelengths of 488 and 514 nm. A LaserTek Model 41 AK laser operating from 488-514nm in conjunction with a Zeiss Model 30 SL-M slit lamp was used to deliver laser radiation and induce lesions. Various powers ranging from 10-40mW were used to obtain both suprathreshold and subthreshold lesions. Subthreshold is defined a laser application that does not cause any minimal visible lesion (MVL). The lesions were imaged immediately post-irradiation and weekly for 5 weeks to follow any changes.
Individual lesions, both suprathreshold and subthreshold, were easily visualized immediately following laser treatment using HRA I in 488 and 514 autofluoresence mode. In fluorescence mode laser lesions appear as spots with reduced fluorescence relative to a broadly fluorescent background. In contrast, the same lesions visible by fluorescence were difficult to visualize in IR reflectance mode. Animals followed on a weekly basis reveal dynamic changes that begin with decreased autofluorescence immediately after laser treatment to increased autofluorescence at five weeks follow up.
Autufluorescence imaging of retina shows that alterations to the RPE occur at laser powers below those that cause minimal visible lesions and offer potentially a highly sensitive technique for assessing the influence of exposure parameters on laser-induced lesion in the retina.
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