To evaluate the effect of alpha lipoic acid (ALA) on the occurrence of diabetic macular edema.

Randomised, double-blind, placebo controlled multicentre study. Patients were randomised to the treatment group with 600 mg ALA per day or the placebo group. At each examination we took stereo fundus photographs, HbA1c levels, and performed an ophthalmological examination. Primary endpoint of the study was the occurrence of clinically significant macular edema (CSME) within a follow-up period of 2 years.

Inclusion Criteria:

• Diabetes type II, mild non proliferative diabetic retinopathy,
• Microalbuminuria > 30 mg/L

Exclusion Criteria:

Ophthalmic exclusion criteria

• severe non-proliferative or proliferative diabetic retinopathy
• Macular edema
• Eye diseases interfering with the examinations of the fundus such as preretinal haemorrhage, cataract, vitreous haemorrhage
• Amblyopia
• Best corrected visual acuity (VA) over 0.5
• Glaucoma
• Patients with cataract surgery within a period of three months
• Other relevant retinal diseases
• Non-authorized interventional therapy of diabetic retinopathy (e.g. laser, kryo-coagulation, vitrectomy)
• General exclusion criteria
• Chronic administration of alpha lipoic acid or of more than five successive days during the last twelve months
• Known intolerance/hypersensitivity to alpha lipoic acid
• Type I diabetes mellitus
• Poor metabolic control with HbA1c >10.5 %/dl
• Late sequelae of diabetes with organic manifestation (e.g. dialysis in cases of renal insufficiency, history of kidney transplantation, creatinine > 1.6 mg/dl)
• Poorly controlled arterial hypertension (systolic blood pressure > 160 mmHg and/or diastolic blood pressure > 95 mmHg)
• Severe disturbances in lipid metabolism (triglycerides > 500 mg/dl or total cholesterol > 320 mg/dl)
• Unpermitted concomitant medication defined as any medicine with a potential interaction with alpha lipoic acid or with the effect of alpha lipoic acid were excluded as concomitant medication. These included aldose reductase inhibitors, substances promoting blood flow, anticoagulants apart from acetylsalicylic acid 500 mg/day and short-term treatment of diseases with the normal dose of acetylsalicylic acid, chronically and systemically administered corticosteroids, hormonal contraceptives
• Malignancies or life threatening diseases
• Drug or alcohol abuse
• Blood donation or blood loss greater than 500 ml) within the last 3 months
• Pregnancy or breast feeding
• Participation in a clinical trial within the last 30 days