Retinal vein occlusion (RVO)-including central RVO, branch RVO, and hemicentral and hemispheric RVO-is the second most common vascular cause of visual loss, surpassed only by diabetic retinopathy. The presence and extent of retinal ischemia in RVO is associated with a worse prognosis. On this basis, most previously conducted studies considered ischemic retinal vein occlusion (iRVO) and non-iRVO as separate entities based on set thresholds of existing retinal ischemia as determined by fundus fluorescein angiography. Other diagnostic technologies have been used specifically in the differentiation of ischemic central retinal vein occlusion and nonischemic central retinal vein occlusion. To date, there is no fully accepted definition for iRVO. Some clinicians and researchers may favor establishing a clear differentiation between these forms of RVO; others may prefer not to consider iRVO as a separate entity. Whatever the case, retinal ischemia in RVO confers a higher risk of visual loss and neovascular complications; thus, it should be determined as accurately as possible in patients with this disease and be considered in clinical and experimental studies. Most recently conducted clinical trials evaluating new treatments for macular edema secondary to RVO included none or only few patients with iRVO based on previous definitions (i.e., few patients with sizeable areas of retinal ischemia were recruited in these trials), and thus it is unclear whether the results observed in recruited patients could be extrapolated to those with retinal ischemia. There has been scant research aiming at developing and/or testing treatments for retinal ischemia, as well as to prevent new vessel formation as a result of RVO. We provide a detailed review of the knowledge gathered over the years on iRVO, from controversies on its definition and diagnosis to the understanding of its epidemiology, risk factors and pathogenesis, the structural and functional effects of this disease in the eye and its complications, natural history, and outcomes after treatment. In each section, the definition of iRVO used is given so, independently of whether iRVO is considered a separate clinical entity or a more severe end of the spectrum of RVO, the information will be useful to clinicians to determine patient's risk, guide therapeutic decisions, and counsel patients and for researchers to design future studies.

Experimental animal models of RVO are available to study the pathogenesis of this disease and to evaluate diagnostic/prognostic biomarkers and to develop new therapeutics. Data available suggest laser-induced RVO in pigs and rodents to be overall the best models of BRVO and the laser-induced RVO rodents the best model for CRVO.

To assess the efficacy of using autologous stromal vascular fraction (SVF) to promote healing of controlled fistula tracts in the management of postoperative upper gastrointestinal leakage. This is an experimental study conducted on 10 experimental rabbits. Animal models were divided into the SVF group which received an autologous SVF and the control group which did not receive the implantation. Surgery was performed on both groups to induce a gastric leak and create a controlled fistula tract between the leakage site in the stomach and the skin. After 2 weeks, surgery was performed on the SVF group to harvest, process and then implant the autologous SVF in the fistula tract. Animal models were followed up and their fistula tracts were evaluated for healing by gross and microscopic examination of the fistula tracts before the SVF implantation and at 24 hours, 1 week, 2 weeks and 3 weeks after implantation. The control group revealed no closure of fistula tracts by the 3 rd week after implantation and there were no signs of inflammation or drainage. On the other hand, the SVF group showed signs of healing process with progressive closure of the fistula tract to about 95% by the 3 rd week after implantation. The use of autologous SVF implantation to promote