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Anat Loewenstein, Michaella Goldstein, Adiel Barak, Dafna Goldenberg, Nurit Erlik, Neil M. Bressler; Sub-threshold Laser Treatment of Macular Edema in Patients with Diabetes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):417. doi: https://doi.org/.
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The objective of this study is to determine the effects of sub-threshold laser treatment in eyes with non-central diabetic macular edema through one year.
This prospective study includes patients with diabetic macular edema with at least one spectral domain optical coherence tomography (SD-OCT) inner or outer subfield macular thickness >2 standard deviations of the expected norm and a central subfield thickness ≤ 315 μm. Baseline evaluations include best-corrected visual acuity (BCVA) testing on an ETDRS chart, stereoscopic color and red-free photographs, fluorescein angiography (FA) and SD-OCT. Eligible patients are treated using a 527 nm laser (train of 30 1.7 microsecond pulses per shot) with a spot size of 200 μm. For each patient, 70% of the minimal energy required to produce a visible spot is applied to areas of macular thickening as determined by clinical examination and SD-OCT. Follow-up visits are at 4, 8, and 12 months after treatment. Patients are eligible for re-treatment (conventional photocoagulation/intravitreal Anti-VEGF injections) if subfield macular thickness (SD-OCT) is increased by >10% and at least >30 μm compared to baseline or if central subfield > 315 μm at each follow-up visit.
Twenty-four patients have been enrolled to date. Of 18 consecutive patients enrolled at least 1 year ago, 17 patients completed the 12-month follow-up visit. The mean change in BCVA from baseline to the 4- and 12-month follow-up visits, respectively, were +2.4 letters (95% CI:-2 to +10) and +4.2 letters (95% CI:-5 to +22). In 12 patients, OCT improved to within normal limits in treated areas. Intravitreal bevacizumab was injected in one other patient at the 4-month visit and additional macular photocoagulation was applied to another patient at 12 months due to an increase in macular thickness of >10% of baseline on SD-OCT. Three patients showed decrease in macular thickness but did not achieve normal limits in all SD-OCT subfields by month 12. Notably, analyzing the areas where the laser was applied with SD-OCT, the RPE layer as well as the outer and inner retinal layers appeared undamaged with no sign of scarring or malformation.
This is the first prospective clinical trial using the Lumenis Novus SRT sub-threshold laser for treating diabetic macular edema. Thus far, 24 out of 102 patients have been enrolled in the study and no serious adverse events were noted with SRT while resolution of DME with sub-threshold treatment was documented. Continued enrollment at multiple sites with longer follow-up is planned to confirm the potential value of these preliminary results.
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