I've been using Osta and S4 for about 6 weeks now. On and off I've had to discontinue the S4 with vision issues. At one point it really freaked me out. I had been splitting 35mg ED with yellow tint, light adjustment issues just like everyone else. I took a few days off and then boosted up to 50mg ED. After about 4 days I could not see in low light at all. I have an LED night light in my room which allows for a bit of light to enable seeing furniture, walls, doors, etc. I asked my wife "who took the night light out" since it was pitch black. All I was able to see was some random LED lights from electronic devices. I looked down and over the edge of the bed and low and behold the night light was there but the light looked yellowish and very dim. I was scared to death. Had to feel my way around (my sexy wife, lol) which lead to something positive.
The next morning, I woke up with a pinhole in my vision that if I looked through that part I could see fine but if I looked through all around it was dark, like sunglasses with a little hole in the center. Progressively, each day the vision got better and took about 4 days to get to 90% clear. I started the S4 again at 35mg ED and the side effects were less severe. I never let it get to total night blindness again.
I still get patches of dark spots in my vision which is most notable when I wake up and it's still dark as the shades are letting in a bit of light. That is when it is most noticeable that the dark spots are there. Otherwise in normal light conditions it's not noticeable. Right now I'm at 3 days off and have a little dark spots which have remained persistent on the peripheral vision. I will judge tonight if it fades away. If not then I will most likely discontinue the S4 completely. If I see some signs of improvement then I will take it slow again. Brand new bottle arrived 3 days ago. Maybe the brand I am using is potent as for me, I get those sides very easily. I have noticed all the positives with the product. I got mine from an American company, all of it.