The S4 definitely has visual side effects. I've really not noticed 'blurry' vision, but it does give light a yellow hue, especially about 30 minutes after dosing. And my night vision is worse. While driving I now drive with the sun visor down and just adjust the tilt of my head to block direct light from oncoming traffic, but I drive mainly country highway at night and don't encounter a lot so this works for me. It's not enough of an issue to change my dosing, I just deal with it. Now if in your line of work you deal with colors, like wiring, this may be an issue as the yellow hue is added to the colors you see changing the appearance. This tells me the S4 is in every part of my body, I assume it has infiltrated the aqueous chamber that covers the lens of the eye. I'd say it took about 1.5 weeks for maximum saturation as this is the time I noticed the night vision hitting the worse point. Been running the S4 for 3 weeks now and I notice increased strength and stamina in lifting. But I am also running MK677 and LGD4033. I started the S4 and LGD at the same time, but MK677 have been running for 5 weeks and I already notice a change in my body composition. Strength up, and look better in the mirror. I've also changed my diet so this is also a factor.