I am feeling an eye flash in my left eye for the past 30-40 days.It is an oval shaped flash when I open and close my eye frequently ,It appers and become visible.Also I am feeling darker and smaller images from left eye as compared to right one.

If you are over ~50 years old, flashes, dark floaters, and loss of visual field are common and are usually signs of age related conditions such as cataracts and retinal scarring. But you DO need an eye exam because other conditions are possible that can lead to blindness. If you experience a sudden worsening (especially graying of your visual field), don't hesitate even one day.