Diabetic retinopathy is still the leading cause of visual impairment worldwide. In the past, severe proliferative diabetic retinopathy (PDR) was regarded as an untreatable and blinding condition. Vitreous hemorrhage due to PDR was an indication for the very first pars plana vitrectomy (PPV) performed in 1970 by Machemer. Since then, the vitrectomy came a long way. The advent of a micro-incisional vitrectomy system and a better visualization system revolutionized the era of vitrectomy in diabetic retinopathy. Vitrectomy machines are increasingly advanced with high-speed cutting rates and optical intraoperative intraocular pressure control, as well as visualization equipment. The number of indications for PPV in PDR is increasing. From nonclearing vitreous hemorrhage (VH) or tractional or combined tractional and rhegmatogenous retinal detachment with diabetic macular edema, vitreomacular traction, and epiretinal membrane. Anterior segment ischemia such as neovascularization of the iris and neovascular glaucoma is currently considered as indications for vitrectomy. Combined cataracts and PPV are commonly performed to improve the intraoperative visualization during vitreoretinal surgery. Timing of PPV is a critical consideration for retinal surgeons in PDR.

Vitrectomy in PDR remains the most challenging condition, even with the most experienced surgeons. There are several approaches to initiating diabetic PPV. There are many techniques for relieving tangential traction – delamination, segmentation, and en bloc dissection. A bimanual technique has also been described for tractional retinal detachment with good visual outcomes and rate of reattachment. The introduction of preoperative adjuncts such as antivascular endothelial growth factor agents has reduced the risk of intraoperative and postoperative bleeding. Postoperatively after PPV, patients are monitored closely to evaluate for further complications, such as recurrent neovascularization, vitreous hemorrhage or diabetic macular edema, retinal redetachments, proliferative vitreoretinopathy, as well as cataract and epiretinal membrane formation. The goal for diabetic retinopathy surgical treatment is not only to prevent blindness but also to maintain good visual acuity after vitrectomy, thus patients with better and better visual acuity are selected for surgery. Macular microstructural changes can now be assessed better with higher resolution optical coherence tomography (OCT) and OCT-angiography. There is also growing evidence favouring vitrectomy for diabetic macular edema refractory to laser and medical therapy.

This Special Issue invites clinicians to provide novel insights into the treatment of complications of proliferative diabetic retinopathy and diabetic macular edema including minimally invasive vitreoretinal surgery techniques and pharmacologic interventions.

Potential topics include but are not limited to the following:

• Systemic conditions influencing the results of surgical treatment in PDR
• Imaging of the vitreoretinal interface before and after vitrectomy
• Long-term monitoring of the anatomical and functional results of surgical treatment of PDR
• Preoperative use of intravitreal anti-VEGF agents
• Chromo-assisted vitrectomy
• Timing of PPV in PDR
• Novel surgical techniques in releasing vitreoretinal traction
• Management of intra- and postoperative complications of vitrectomy
• Results of vitrectomy in tractional and nontractional diabetic macular edema