Difficulties in recruiting participants

Vitrectomy is the common treatment for patients with macular edema secondary to epiretinal membrane. Recently, in eyes with diabetic macular edema or persistent macular edema following retinal vein occlusion, vitrectomy will be increasingly performed as an additional treatment modality. In eyes with impaired oxygen situation vitrectomy may improve the retinal oxygen saturation. However, little information is available about the oxygenation and the blood flow of the retinal vessels after vitroretinal surgery.

Hypoxia is a the major trigger of vascular endothelial growth factor (VEGF), which is in turn the most important factor for the development of macular edema. It is a major issue to improve the oxygen situation and the blood flow of the retina and there are just a few not satisfactory procedures available to overcome this problem. However, vitrectomy would be an adequate therapy for many of these diseases, and it would be an appreciated side effect of the treatment in almost every case.

To investigate the influence of oxygenation and blood flow of the retina on clinical outcomes after a successfully 23 gauge vitrectomy in eyes with epiretinal membrane, persistent macular edema following diabetic retinopathy or retinal vein occlusion.

Inclusion Criteria:

• male or female, at least 18 years of age.
• ophthalmoscopic evidence of epiretinal membrane scheduled for vitrectomy and membrane peeling.
• persistent diabetic macular edema
• written informed consent
• female patients of childbearing potential must have a negative urine pregnancy test.

Exclusion Criteria:

• uncontrolled systemic disease
• symptoms of a clinically relevant illness in the 3 weeks before the first study day
• any ocular condition that in the opinion of the investigator would be a contraindication for the surgical procedure
• history of glaucoma, aphakie or presence of anterior chamber intraocular lens, choroidal neovascularisation, significant cataract, any ocular infection, - history of pars plana vitrectomy.
• contraindication to pupil dilation.
• need for silicon oil or gas after the surgery
• advanced diabetic retinopathy with vitreoretinal tear and/or bleeding

Group 1: 20 patients with macular edema following epiretinal membrane Group 2: 20 patients with persistent diabetic macular edema. Group 3: 20 patients with persistent macular edema following retinal vein occlusion