It seams your mother is suffering from age related retinal degeneration
or some retinal vascular disease
left > right eye (details not clear from your query). Injections are given in the eye to decrease the swelling with in the retina to save/recover whatever possible eye sight she can get. Since her eye condition is not good and you look confused I strongly advice you to take a second opinion
with a vitreo-retinal eye specialist. Hope your mother recovers fast. All the best.