Response to subthreshold micropulse laser treatment in the prophylaxis of diabetic macular oedema: A preliminary study.

Purpose: To evaluate the use of subthreshold micropulse laser (SMPL) in the prevention and management of mild diabetic macular oedema (DME).

Methods: This prospective, randomised and sham-controlled study included 159 eyes (123 patients) with diabetic retinopathy, central retinal thickness (CRT) ≤ 325 μm, and best-corrected visual acuity (BCVA) ≥ 80 ETDRS letters. The participants were assigned to either SMPL treatment (n = 103) or sham therapy (n = 56). Ophthalmic evaluations were performed at baseline (T1), 3 months (T2) and 12 months (T3) to assess BCVA and optical coherent tomography (OCT) parameters, including CRT, macular thickness (MT), macular volume (MV), and hyperreflective spots (HRS).

Results: In the SMPL group, BCVA improved after 3 months (T2 > T1; p = 0.002); MT decreased after 12 months (T2, T1 > T3; p < 0.001); MV decreased after 12 months (T2, T1 > T3; p < 0.001); HRS count decreased after 3 and 12 months (T1 > T2, T3, p < 0.001). The decrease in CRT after 3 months was greater in the SMPL group (p = 0.003). The need for rescue therapy was lower in the SMPL group (9.7% vs. 19.6%, p = 0.007). BCVA, CRT, MV, MT and HRS remained stable in the sham group, while microaneurysms count was stable in both groups.

Conclusion: SMPL is safe and effective for the prophylaxis of mild DME, as it reduces MT and MV while keeping BCVA stable. The decreased need for rescue anti-vascular endothelial growth factor therapy suggests that it may delay or reduce intravitreal injections.