Purpose:
SW-AF has been suggested as being useful in identifying laser scars in the diabetic macula. We compared short wave autofluorescence (SW-AF) and near infra-red reflectance (NIR-RF) imaging for the identification of scars in diabetic macular oedema (DMO).
Methods:
Patients with a history of macular laser for DMO underwent imaging using SW-AF (excitation 488nm, detection >500nm), NIR-RF (emission 820nm) and NIR-AF (excitation 788nm, detection >820nm) using a Heidelberg HRA2 scanning laser ophthalmoscope (SLO). Images were graded by two medical retina specialists (AR, JS) for visibility and proportion of border that is delineated: 0 (none visible), 1 (<50% border delineated), 2 (50-90%), 3 (>90%). Mann-Whitney U and Kappa analysis was performed using SPSS version 19.
Results:
18 eyes of 17 patients were included. The appearance of laser scar was as follows: on SW-AF a focus of hyperfluorescence with a surrounding ring of hypofluorescence (Fig 1a); on NIR-RF a focus of hyper-reflectance, occasionally surrounded by a ring of hyporeflectance (Fig 1b); and on NIR-AF a focus of hypofluorescence with an occasional central spot of hyperfluorescence (Fig 1c). Agreement between graders was good: same grade assigned 85%; within 1 grade 100% (Κ = 0.722). 3 eyes (16.7%) did not demonstrate laser scars on SW-AF; these were visible in all on NIR-RF and NIR-AF. Although NIR-RF and NIR-AF provided clearer imaging of laser scars as compared to SW-AF, the difference did not reach statistical significance (p=0.19 and 0.45 respectively). Reflectance was easier to collect in most subjects.
Conclusions:
SLO based NIR techniques appear to be useful in detecting laser scars in the assessment of diabetic maculopathy. Based on the experience of our subjects, reflectance may be preferable to autofluorescence.
Keywords: laser • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • diabetes