Abstract
Purpose:
SRT stimulates retinal pigment epithelium (RPE) cell migration and proliferation into irradiated areas using 1.7μs laser pulses, improving metabolism at diseased areas. RPE cells are selectively damaged without affecting the neural retina, photoreceptors or choroid. This is a prospective, interventional, single center, single arm, open label clinical study to evaluate the efficacy and safety of SRT in eyes with clinically significant DME.
Methods:
Twenty-three eyes of 21 consecutive patients (mean age 63.3yrs [48-77yrs]; 7 male) with clinically significant DME were treated with SRT and followed for 6 months with evaluations at 1 week, 1, 3 and 6 months. 86.9% had received prior DME treatment, including intravitreal anti-VEGF, subtenon triamcinolone and conventional laser. Evaluations included: Fundus fluorescein angiography, reflectometry, optical coherence tomography and macular sensitivity using microperimetry within central 10° field. Key outcome measures included: Proportion of eyes gaining ETDRS letters in BCVA from baseline, mean changes in BCVA, central macular thickness (CMT), maximum macular thickness (MMT) and macular sensitivity and incidence of adverse events over the follow-up period. Patients who met retreatment eligibility criteria could be retreated after a period of 2 months.
Results:
Seventeen eyes (16 patients) completed 6 months follow up. Mean BCVA improved from 67.7±11.1 letters at baseline to 73.71±11.9 at 6 months. The proportion of eyes gaining ≥5, ≥10 and ≥15 letters were 41.2%, 17.6% and 11.8% respectively. Two eyes lost ≥5 letters, but neither had considerable deterioration in OCT findings or macular sensitivity. Nine eyes (53%) showed >5% decrease in MMT compared to baseline at 6 months. Macular thickness decreased from 482.06±96.56μm to 465.06±101.45 (p=0.183) and mean macular sensitivity increased from 21.16±2.9 to 22.38±3db (p=0.019). Retreatment occurred in 12 eyes. No treatment-related adverse events were reported.
Conclusions:
BCVA gains and improved macular sensitivity have demonstrated that SRT, using reflectometric dosimetry, can be an effective treatment for clinically significant DME. The safety profile was acceptable and consistent with previous reports. The absence of collateral damage in the neural retina and choroid and selective effect on the RPE, sparing the photoreceptors makes SRT particularly suitable for treatment of DME.