An experimental light mask, the Noctura 400 Sleep Mask (PolyPhotonix Medical) did not help control non-central diabetic macular oedema, in a recent trial.
In CLEOPATRA, which investigators believe to be the first phase 3 clinical trial of this approach, the light mask was no more effective than a sham mask in reducing retinal thickness.
"The analysis of compliance highlighted that wearing these light masks over 24 months might also not be a sustainable option, as compliance decreased over time," wrote Sobha Sivaprasad of Moorfields Eye Hospital, London, UK, and colleagues, in Lancet Diabetes & Endocrinology.
Diabetes can compromise the capacity of ocular blood vessels to supply oxygen to the retina. This stimulates the development of new blood vessels, which often leak, causing retinopathy and – when the central macula is affected – macular oedema, impairing vision.
Diabetic macular oedema outside the centre of the macula can progress to the centre. Current treatments, which include intravitreal injections of anti-vascular endothelial growth factor (VEGF) agents, steroids and laser treatments, are invasive.
Demand for oxygen in the retina is greatest during dark adaptation, when rod photoreceptors consume nearly all the oxygen available. This observation has led to the hypothesis that macular oedema could be alleviated by preventing dark adaptation, providing a non-invasive supplement to standard treatments.
The light mask is designed to provide 500-505 nm light during sleep without interfering with sleep. A proof-of-concept study using a chemoluminescent source in 12 patients for 3 months suggested the treatment was safe, acceptable to patients and improved both colour vision and microaneurysm count.