• Sudden, painless and complete or partial loss of vision in one eye
• Occurs when a major blood vessel behind the eye becomes blocked. (much like a stroke confined to the eye)
• Medical conditions such as diabetes, raised blood pressure and smoking increase the risk
• Note: If sudden loss of vision occurs get to an ophthalmologist as soon as possible. Sometimes the vision loss is reversible but permanent defects in the vision often remain

Link: www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002023/
eyewiki.aao.org/Category:Retina/Vitreous