Abstract
Purpose: :
Fundus autofluorescence imaging (FAI) is now more widely being used for phenotyping of inherited retinal disease. Because it is based on autofluorescence of fluorophores in the retinal pigment epithelium (RPE), it can also be used as a highly sensitive imaging technique for monitoring short term changes of laser light interaction with retina and wound healing following photothermal therapy.
Methods: :
Retired breeders of pigmented rats at an age of at least 6 months were studied as small animal models. Strong retina autofluorescence signal was observed in this model. A modified Heidelberg Retina Angiograph (HRA I) was used to obtain images of the fundus by autofluorescence at 488 and 514 nm. White light fundoscopy images were also obtained using a small endoscope. A coherent argon laser model was used to photocoagulate the retina at near threshold level, causing barely noticeable minimal visible lesions (MVL). The response of the retina was followed overtime using white light fundoscopy and FAI with two wavelengths
Results: :
Individual laser applications were barely visualized with white light fundoscopy but easily visualized with FAI immediately following laser treatment. Immediately after placing lesions at 13 mW and 15 mW the rats were imaged with a modified HRA I to characterize the laser tissue interaction. The 13 mW lesions appear as hypofluorescent spots in contrast to the RPE. At 15 mW, the center of each lesion shows distinct hyperfluorescence. Follow up imaging at 24 hours revealed the central hyperfluorescent area while the outer hypofluorescent was no longer visible. Most lesions at 13 mW disappeared after 24 hours. At 48 hours, both the 13 and 15 mW lesions reappeared at their original size as hyperfluorescent spots and retained this appearance in subsequent images
Conclusions: :
Rats provide an acceptable animal model to study laser tissue interaction. Autufluorescence shows the lesions better than white light fundoscopy and is a good non-invasive tool for monitoring and characterization of laser therapy in the retina.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retinal pigment epithelium • laser