Diabetic Macular Edema Laser Treatments Equally Effective

The clinical efficacy of subthreshold micropulse laser (SML) is equivalent to that of standard laser (SL) treatment for patients with diabetic macular edema (DME), according to a report published in Ophthalmology.

Researchers analyzed data from the DIAbetic Macular Oedema aNd Diode Subthreshold micropulse laser (DIAMONDS study, ClinicalTrials.gov Identifier: NCT03690050), a multicenter, allocation-concealed, double-masked, randomized, noninferiority trial to compare the safety, efficacy, and cost outcomes of SML and SL for the treatment of diabetic macular edema (DME). The trial included adult patients with center-involved DME with central retinal thickness (CRT) of less than 400 μm and best-corrected visual acuity (BCVA) of more than 24 Early Treatment Diabetic Retinopathy Study (ETDRS) letters in a single eye or both eyes. 

Patients were randomized (1:1) to treatment with 577 nm SML (n=133) or SL (n=133). Retreatment and rescue with intravitreal anti-vascular endothelial growth factor (VEGF) therapies or steroids (if >10 ETDRS-letter loss occurred and/or CRT increased to >400 μm).

The primary outcomes of the study were mean change in BCVA in the study eye at 24 months (noninferiority margin, 5 ETDRS-letters), and secondary outcomes included mean change from baseline to 24-month binocular BCVA, CRT, and mean deviation of 10-2 visual fields (VF) in the study eye. The percentage meeting driving standards, EuroQoL survey results (EQ-5D-5L), National Eye Institute-Visual Function Questionnaire (NEI-VFQ25), and Vision and Quality of Life Index (VisQoL) scores were also secondary outcomes. The researchers also accounted for cost per quality-adjusted life year (QALY) gained, adverse effects, and number of laser and rescue treatments.

The study obtained primary outcome data for 87% of the SML group and 86% of the SL group. The study shows a mean BCVA change from baseline to 24 months of -2.43±8.20) in the SML group and -0.45±6.72 in the SL group. The researchers report that SML was not only noninferior, but also equivalent to SL, reporting that the 95% confidence interval (CI) (-3.9 to -0.04) fell within the upper and lower margins of the permitted maximum difference (5 ETDRS letters). 

“We chose central vision as the primary outcome, as this is most important to people with diabetes and DME and set the non-inferiority margin at 5 ETDRS letters (equivalence margin as +5 ETDRS letters) as visual changes of this size or under it are unlikely to be clinically relevant to patients and could be even attributed to test/retest variability,” researchers report.

The team found no statistically significant differences in binocular BCVA (0.32 ETDRS letters; 95% CI, -0.99 to 1.64; P =.63), CRT (-0.64 µm; 95% CI, -14.25 to 12.98; P =.93), mean deviation (0.39 dB; 95% CI, -0.23 to 1.02; P =.21), meeting driving standards (% point difference, 1.6; 95% CI, -25.3 to 28.5; P =.91), adverse effects (risk ratio, 0.28; 95% CI, 0.06-1.34; P =.11), rescue treatments (% point difference, -2.8; 95% CI, -13.1 to 7.5; P =.59), or EQ-5D/VFQ-25/VisQoL scores. They reported that the number of laser treatments was higher with SML than SL (difference, 0.48; 95% CI, 0.18-0.79; P =.002), but found no differences in base-case analysis costs or QALYs.

Limitations of the study include poorly controlled diabetes in the majority of participants, no robust data supporting the use of +5 ETDRS letters as the margin for equivalence, and an inability to compare clinical efficacy and cost effectiveness of macular laser (SL or SML) vs anti-VEGF therapy.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.