What Causes Double Vision While On Actonel For Osteoporosis?

I m 78, and still do Hormone replacement therapy. I was recently diagnosed with osteoporosis. At least 8 years ago I took 5 pills of Actonel over 5 weeks. By the 5th pill I wakened with a headache which did not respond very quickly to Excedrin but worse, I had double vision. I was sent to a neuropthamalogist with full eyes . He never found a cause. I believe it was the Actonel because it never happened again. Now my GYN wants me to start Prolia. A friend researched it and opted not to. I m really scared it might cause problems, as Actonel was the only drug reaction I ve had. (The dr. insisted that did not cause it, but I never experienced anything like it before or after. What do you advise?