Selective retina therapy (SRT) for clinically significant diabetic macular edema

Purpose: To test selective retina therapy (SRT) as a treatment of clinically significant diabetic macular edema (DME). Methods: Prospective two-center interventional uncontrolled phase II pilot study. Thirty-nine eyes of 39 patients with previously untreated non-ischemic DME were treated with focal laser treatment using a Q-switched frequency doubled Nd:YLF laser which selectively affects the retinal pigment epithelium while sparing the photoreceptor layer. Optoacoustic measurements, fundus fluorescein angiography (FFA), and funduscopy were used to determine the individual threshold of RPE damage of each patient. The pulse energy was adjusted to apply angiographically visible but funduscopically invisible effects. Optoacoustic measurements were correlated with funduscopy and FFA. Follow-up examinations at 3 and 6 months post-treatment included best-corrected ETDRS visual acuity (BCVA), FFA, fundus photography, and retinal thickness measured by optical coherence tomography. The primary outcome measure was change of BCVA. Other outcome measures were change of retinal thickness, presence of hard exudates, leakage in FFA, accuracy of optoacoustic measurements, and correlation of BCVA with change of anatomical and systemic parameters. Results: Mean BCVA improved from 43.7 letters (standard deviation, SD = 9.1) at baseline to 46.1 letters (SD = 10.5) at the 6-month follow-up (p = 0.02). BCVA improved (>5 letters) or remained stable (±5 letters) in 84% of eyes. Thirteen percent of eyes improved by ≥ 10 letters, while 16% of eyes lost more than 5 letters. There was no severe loss of vision (≥ 15 letters). Overall, retinal thickness, hard exudates, and leakage in FFA did not change significantly (p > 0.05), while improvement of BCVA correlated with a reduction of hard exudates (p = 0.01) and central retinal thickness (p = 0.01). Specificity and sensitivity of detecting the angiographic visible threshold of RPE damage by optoacoustic measurements were 86% and 70% respectively. No adverse effects or pain were noted during or after treatment. Conclusions: Functional and anatomical improvement or stabilization was observed in most patients. SRT appears to be safe. Optoacoustic measurements accurately detect the individual threshold of RPE damage. A randomized trial is required to further test efficacy and safety of SRT as a treatment of clinically significant diabetic macular edema (DME).