Abstract
Purpose :
Subthreshold laser treatment of diabetic macular edema (DME) enables selective treatment of chorioretinal microstructures with less deleterious effects on the photoreceptors and retinal pigment epithelium (RPE) cells than regular continuous wave laser. This comparative study is aimed to assess morphological changes after application of different technologies.
Methods :
This is a retrospective, comparative study. Patients with clinically significant DME who received subthreshold laser either with 577 nm μpulse technology (μp) or 577 nm continuous wave laser with endpoint management (EM) were included. Changes in retinal morphology due to laser-tissue interaction were assessed before and 1 hour, 1, 7, 14, 30, and 60 days after treatment with color and red-free fundus photography, blue-light and near-infrared fundus autofluorescence, and spectral-domain optical coherence tomography (SD-OCT). Subthreshold μp laser irradiation was performed with 5% duty cycle. Subthreshold EM laser irradiation was performed using the endpoint management algorithm at 30% energy.
Results :
Twenty-eight eyes were included in the study. Eleven eyes were treated with μp laser irradiation and 17 eyes were treated with EM. Mean (±SD) powers used for non-visible laser irradiation were 508±182 mW in the μp group and 288±99 mW in the EM group. Morphological changes due to laser-tissue interaction were most evident in blue-light fundus autofluorescence as an early hyper-autofluorescent area that then became hypo-autofluorescent at later follow-up timepoints. This finding was present in 9%, 27%, 36%, 27%, and 27% (μp) and 35%, 53%, 53%, 53%, and 53% (EM) of cases after 1 hour, 1, 7 ,14, 30 and 60 days after treatment. At SD-OCT, disturbances of RPE layer were less evident in the μp group than in the EM eyes.
Conclusions :
The characteristic in vivo effects of sub-visible retinal photocoagulation were monitored over time by the use of different imaging techniques. Best imaging systems in detecting retinal changes are fundus autofluorescence and SD-OCT. Differences exist between the two subthreshold laser technologies. The most remarkable being the more subtle and grainy appearance of μp spots in both fundus autofluorescence and SD-OCT images when compared to EM. In a large proportion of cases, laser-irradiated areas were not detectable with either sub-threshold laser technology.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.