Unexpected poor enrollment

The prevalence of diabetes mellitus (DM) is increasing worldwide. Diabetic retinopathy is the most prevalent complication of DM and a leading cause of visual impairment. Some factors are known to temporarily aggravate or improve diabetic retinopathy, but underlying pathophysiologic factors are still unknown. High-resolution imaging techniques of the retina and its supplying vascular networks now allow novel insight to subtle changes that cannot be appreciated in standard fundus examination. In detail, the investigators image study patients with optical coherence tomography (OCT) - technology, that provides morphological information of retinal structure and the supplying vessels in a non-invasive way. Retinal layer thickness as well as capillary density will be quantified and followed in patients that are in a critical period of disease transition to better understand the process of diabetic retinopathy.

Inclusion Criteria:

• Diabetes mellitus type 1 or 2
• Age 18-90

Exclusion Criteria:

• Media opacities like cataract or vitreous hemorrhage
• Active intraocular inflammation (grade trace or above) in either eye like infectious conjunctivitis, keratitis, scleritis, endophthalmitis as well as idiopathic or autoimmune-associated uveitis in either eye
• Structural damage to the center of macula in the study eye
• Atrophy of retinal pigment epithelium, subretinal fibrosis, laser scar within foveal avascular zone (FAZ) or organized hard exudate plaques
• Ocular disorders in the study eye including retinal vascular occlusion, retinal detachment, macular hole, choroidal neovascularization, macula dystrophies
• Intraocular surgery (including cataract surgery, YAG laser capsulotomy) in the study eye within 3 months preceding Day 0, or history of corneal transplantation in the study eye
• Uncontrolled glaucoma in the study eye (defined as intraocular pressure ≥ 25 mmHg despite treatment with anti-glaucoma medication)or history of glaucoma filtration surgery
• Inability to obtain fundus photographs or fluorescein angiograms of sufficient quality to be analyzed and graded

Patients with diabetes type 1 or 2 that enter a critical period of possible disease transition will be recruited in a tertiary referral center.