Aim: To report the evolution of pattern scanning laser (Pascal®) photocoagulation burns in the treatment of diabetic retinopathy, using Fourier-Domain optical coherence tomography (FD-OCT) and fundus autofluorescence (AF), and to evaluate these characteristics with clinically visible alterations in outer retina (OR) and retinal pigment epithelium (RPE).
Methods: Standard red-free and colour fundus photography (FP), FD-OCT, and fundus camera-based AF were performed in 17 eyes of 11 patients following macular and panretinal photocoagulation (PRP).
Results: One hour following Pascal® application, visibility of threshold burns on FP was incomplete. AF enabled visualization of complete treatment arrays at one hour, with hypo-autofluorescence at sites of each laser burn. AF signals accurately correlated with localised increased optical reflectivity within the outer retina on FD-OCT. AF signals became hyper-autofluorescent at 1 week, and corresponded on FD-OCT to defects at the junction of the inner and outer segments of the photoreceptors (JI/OSP) and upper surface of RPE. A 10ms macular laser pulse produced a localized defect at the level of JI/OSP and RPE. Macular and 20ms PRP burns did not enlarge at one year and 18 months follow-up respectively.
Conclusions: We report the in vivo spatial localization and clinical correlation of medium-pulse Pascal® photocoagulation burns within outer retina and RPE, using high-resolution FD-OCT and AF. Ophthalmoscopically invisible and threshold Pascal® burns may be accurately localized and mapped by AF and FD-OCT, with monitoring of over time.