Please explain what are some symptoms of vitreous haemorrhage and retina detachment after retrobulbar injection?

Not from injection: Vitreous separation can rip the retinal and retinal blood vessels causing a vitreous hemorrhage and retinal detachment. Vitreous hemorrhage causes floaters. Detachment occurs as fluid flows though untreated tears and the retina falls off the back of your eye-like wallpaper coming off a wall. This causes a veil in your side vision then central vision loss. This isn't from retrobulbar injection.

Loss of vision: If there is inadvertent puncture of the eye during injection. Symptoms would be blurry vision, haze, curtain or shadow. This is a serious complication that can lead to loss of sight. It typically happens in myopic eyes which are longer and with a sharp rather than blunted tip needle. It often requires surgical repair and visual prognosis depends on what areas are damaged.