Light and diabetic eye disease

INTERVENTION: Patients will sleep wearing a device ('light mask') that illuminates one (closed) eyelid. The eye is chosen at random. The other eye acts as control. Each patient will be treated for 6 months CONDITION: Diabetic retinopathy ; Eye Diseases ; Other disorders of eye and adnexa in diseases classified elsewhere PRIMARY OUTCOME: 1. Ocular coherence tomography (OCT) ; 2. Microperimetry ; 3. Colour contrast sensitivity; 4. Visual acuity; 5. Digital fundus photography with quantitative analysis of microaneurysms ; ; Investigations are made at baseline, 3 and 6 months INCLUSION CRITERIA: 1. Adults age 18‐65 2. No systemic disease apart from diabetes (type I or II) 3. Symmetrical DME which cannot be treated surgically, or does not require immediate intervention