Abstract
Purpose: :
To demonstrate the utility of dual wavelength fundus autofluorescence (FAF) imaging for non-invasive, quantitative monitoring of dynamic changes associated with healing of retinal photocoagulation lesions in a small animal model.
Methods: :
Brown-Norway rats (~9 Months), exhibiting substantial age dependent lipofuscin autofluorescence, were used to characterize kinetics of AF recovery following retinal photocoagulation. An argon laser with a beam diameter of 100 µm, exposure duration of 0.1 seconds and a range of laser powers from 5-40 mW was used to create subthreshold, threshold and suprathreshold lesions. A modified Heidelberg Retinal Angiograph I (HRA I) was used to obtain dual wavelength FAF images at 488 and 514 nm that were used to quantify and monitor changes in retinal fluorescence for up to six months.
Results: :
Compared to white light fundoscopy, the FAF images exhibited heightened definition and clarity of lesion boundaries immediately following laser exposure. Laser exposures at and above 13.5 mW resulted in significant reduction of FAF immediately after the lesions were created (P<0.001). No significant reduction in FAF was measured at or below laser powers of 8 mW. Furthermore, a linear, dose-dependent decrease in FAF (R2 = 0.9605) was observed immediately following laser exposure. Complete recovery of baseline FAF was observed for 13.5 and 16 mW exposures at 3 weeks and 4 months, respectively. However, retinal damage was still evident at 6 months following suprathreshold exposure induced using 22 mW laser power.
Conclusions: :
The accumulation of lipofuscin in the aged brown Norway rat makes this a suitable small animal model for the characterization of laser induced injury in the retina based on FAF. Dual-wavelength FAF measurements provide a sensitive, quantitative, non-invasive means of monitoring recovery of laser induced retinal injury.
Keywords: laser • ipofuscin • retina