Although researchers know hypoxia contributes to diabetic macular edema (DME), a novel therapy option using a mask that emits 500nm to 505nm light to stop dark adaptation may not be the answer. Rod photoreceptors consume the most oxygen for dark adaptation, suggesting any therapy that prevents rod-related dark adaptation could stave off DME progression.

Researchers in the United Kingdom tested this theory with a Phase III clinical trial that included 308 participants. During the study, 155 participants with non-center-involved DME wore a light mask at night for 24 months. Follow-up every four months showed no difference in effect compared with the control arm of 153 patients. While the primary outcome was a change in maximal retinal thickness, measured by spectral-domain optical coherence tomography, the study also recorded the reduction in total retinal thickness, macular volume, progression of central subfield thickness to ≥300µm, the number of participants requiring treatment for new-onset center-involving DME and the number of participants requiring standard therapy during the trial due to worsening DME. All of these parameters showed no significant difference between the treatment and control arms.

The researchers admit treatment compliance and participant dropout were both significant issues. Non-compliance became a concern as early as the first four-month follow-up visit, “highlighting that offering these light masks to wear during sleep is not an effective option for this condition,” the study notes.

Despite the light mask’s subpar performance, “our study results encourage more research on interventions for non-central DME,” the researchers wrote in their paper. Until more research reveals better preventative therapies, clinicians should focus on controlling systemic risk factors, the study concludes.

Sivaprasad S, Vasconcelos J, Holmes H, et al. Lightmasks that prevent dark adaptation for non-central diabetic macular oedema: the CLEOPATRA RCT. Efficacy and Mechanism Evaluation, No. 6.2. Southampton (UK): NIHR Journals Library; 2019 Feb.