What Causes Extreme Blurriness In Eyes After Injection Avastin?

I have taken Evista for over 20 years with no side effects to prevent breast cancer and bone loss. I am 73 years old and in very good health. Two months ago I had a BRVO in my right eye and I am distressed about it. Have had two injections of Avastin which improves the sight for three to four weeks and then the extreme bluriness returns. Are there substitutes for this drug which would do the same thing but not cause blood clots?