Light Mask to Inhibit Dark Adaptation Does Not Prevent Diabetic Macular Edema Progression

Diabetic retinopathy.
Diabetic retinopathy.
The CLEOPATRA study provides evidence that the light mask offered to prevent dark adaptation is not recommended as a treatment option for non-center-involving diabetic macular edema.

An organic light-emitting sleep mask did not offer long-term therapeutic benefit in patients with non-central diabetic macular edema, according to the results of the CLEOPATRA study published in The Lancet Diabetes-Endocrinology.

Diabetes decreases the retinal oxygen supply. During dark adaptation, normal rod photoreceptors in the retina consume nearly all the oxygen available to the eyes. It is hypothesized that hypoxemia during dark periods may exacerbate microvascular changes and that an environment illuminated with 500 to 505 nm of light should suppress rods and prevent or reverse diabetic macular edema. Results from a few small studies have demonstrated some efficacy with no safety issues.

CLEOPATRA was a phase 3, single-blind, parallel-group, randomized, controlled trial conducted in 15 ophthalmic centers in the United Kingdom (Controlled-Trials Number: ISRCTN85596558). Study researchers randomly assigned adults with non-central diabetic macular edema to either a light mask during sleep or a sham mask for 24 months between April 10, 2014 and June 15, 2015.  The primary outcome was the change in maximum retinal thickness on optical coherence tomography (OCT) at 24 months, analyzed using a linear mixed-effects model that incorporated 4-monthly measurements and baseline adjustment.

Of 308 patients randomly assigned to one of the two groups, 246 patients had OCT data at 24 months. The change in maximum retinal thickness at 24 months did not differ in the two treatment groups (mean change −9.2 μm for the light mask vs −12.9 μm for the sham mask; adjusted mean different −0.65 μm; P =.84).

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At 24 months, median compliance with wearing the light mask was 19.5%. There were no serious adverse events in either group, and the most frequent adverse events were eye discomfort; painful, stick, or watery eyes; and sleep disturbance, all of which were more common with the light mask.

The investigators suggest that it is possible that the retinal illumination achieved with the light mask was insufficient to alter the hypoxic state, and note that other clinical trials of light masks to prevent dark adaptation in diabetic retinopathy are ongoing and 2 trials are underway for age-related macular degeneration. 

As for the possibility that poor compliance affected the outcome, the researchers argue that there was no discernible treatment effect favoring the light mask at 4 months and 8 months, when compliance was highest, and that this lack of effect remained constant.

“The light mask as offered in this study is not an effective intervention to prevent or treat patients with non-center-involving diabetic macular edema,” the study investigators concluded.


Sivaprasad S, Vasconcelos JC, Prevost AT, et al. Clinical efficacy and safety of a light mask for prevention of dark adaptation in treating and preventing progression of early diabetic macular oedema at 24 months (CLEOPATRA): a multicentre, phase 3, randomised controlled trial [published online March 5, 2018]. Lancet Diabetes Endocrinol.doi:10.1016/S2213-8587(18)30036-6