Creatine is neuroprotective to retinal neurons in vitro but not in vivo

Purpose: To investigate the neuroprotective properties of creatine in the retina using in vitro and in vivo models of injury. Methods: Two different rat retinal culture systems (one containing retinal ganglion cells [RGC] and one not) were subjected to either metabolic stress, via treatments with the mitochondrial complex IV inhibitor sodium azide, or excitotoxic stress, via treatment with N-methyl-D-aspartate for 24 hours, in the presence or absence of creatine (0.5, 1.0, and 5.0 mM). Neuronal survival was assessed by immunolabeling for cell-specific antigens. Putative mechanisms of creatine action were investigated in vitro. Expression of creatine kinase (CK) isoenzymes in the rat retina was examined using Western blotting and immunohistochemistry. The effect of oral creatine supplementation (2%, wt/wt) on retinal and blood creatine levels was determined as well as RGC survival in rats treated with N-methyl-D-aspartate (NMDA; 10 nmol) or high IOP-induced ischemia reperfusion. Results: Creatine significantly prevented neuronal death induced by sodium azide and NMDA in both culture systems. Creatine administration did not alter cellular adenosine triphosphate (ATP). Inhibition of CK blocked the protective effect of creatine. Retinal neurons, including RGCs, expressed predominantly mitochondrial CK isoforms, while glial cells expressed exclusively cytoplasmic CKs. In vivo, NMDA and ischemia reperfusion caused substantial loss of RGCs. Creatine supplementation led to elevated blood and retinal levels of this compound but did not significantly augment RGC survival in either model. Conclusions: Creatine increased neuronal survival in retinal cultures; however, no significant protection of RGCs was evident in vivo, despite elevated levels of this compound being present in the retina after oral supplementation.Paul Ikgan Sia, John P. M. Wood, Glyn Chidlow, Robert Casso

Orbital compartment syndrome following transvenous embolization of carotid-cavernous fistula

Case ReportSuperior ophthalmic vein (SOV) thrombosis is a rare complication of carotid-cavernous fistula (CCF) embolization and is usually associated with a paradoxical worsening of signs followed by subsequent spontaneous resolution. We report a case in a 69-year-old female who developed orbital compartment syndrome due to SOV thrombosis following transvenous embolization of an indirect CCF. The patient was treated with an urgent lateral canthotomy and cantholysis and had good recovery. This report demonstrates that the paradoxical worsening due to SOV thrombosis in CCF may result in orbital compartment syndrome and require early recognition and prompt decompressive measures to avoid permanent visual sequelae.Paul Ikgan Sia, David Ik Tuo Sia, Rebecca Scroop, and Dinesh Selv