Abstract
Purpose: :
To compare spectral domain OCT and autofluorescence findings of two laser photocoagulation techniques for treatment of diabetic macular edema: the modified Early Treatment Diabetic Retinopathy Study (ETDRS) direct/ grid photocoagulation technique and high density (increased number of spots to potentially enhance the area of retinal pigment epithelium activation) sub-threshold micro pulsed 810 nm diode laser technique.
Methods: :
Prospective, double-masked, controlled trial, 30 subjects with previously untreated diabetic macular edema randomly assigned to receive laser photocoagulation by the modified ETDRS Study (direct/ grid photocoagulation) in16 eyes or high density micro pulsed technique (Opto FastPulsetm Laser) in 14 eyes. Visual acuity, fluorescein angiography, autofluorescence (FAF, 488nm), near infra-red autofluorescence (NIRFAF, 790 nm) and spectral domain optical coherence tomography (OCT) were obtained at baseline and at 1, 3 and 6 months. Main outcome were accessed by OCT and FAF/ NIRFAF.
Results: :
No changes to retinal pigment endothelium (RPE) and photoreceptors were observed by OCT or FAF/ NIRFAF of the high density treatment group laser spots. In the modified ETDRS group we could clearly identify every spot by SD-OCT, FAF and NIRFAF, although a low intensity strategy (light grey) was used. SD-OCT showed an increased reflectivity in the RPE cells, which included the outer segment of the photoreceptors, although in the majority of cases the OS/IS line was present. There was no increase in size or area of laser spots in the follow up period.FAF and NIRFAF showed initially a decreased signal, however in time we could observe and increase in FAF and NIRFAF. No difference in central macular thickness and visual acuity was identified between groups.
Conclusions: :
These findings do not support the use of sub-threshold laser treatment of diabetic macular edema, but imply a short-term clinical performance comparable to the modified ETDRS technique, with no scarring observable with SD-OCT and FAF/NIRFAF. OCT findings suggest that a light treatment with continuous laser could selectively treat the RPE minimizing damage to the photoreceptors. The precise role of sub-threshold and threshold laser treatment may become more defined in further studies.
Clinical Trial: :
www.clinicaltrials.gov NCT00552435
Keywords: diabetic retinopathy • laser • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)