Hey guys! Glad to found this thread. I've been wondering the same thing. I'm actually able to voluntarily blur my vision. It's not the same as focusing and de-focusing. From my understanding, focus and defocus is when you look at a specific object, the surrounding is blurry (correct me if I'm wrong). In my case, I can voluntarily blur my vision even towards the thing I'm focusing on. I'm sure it's not a superpower lol but it can be beneficial, at least for me. For instance, when watching horror movies, I could just instantly blur my vision during the scary parts. And the blurriness can be adjusted as well, however I can't do it for too long because it hurts my head. I'm not sure if this is a common thing, I've been asking my friends and family in the past, none of them could do it. I thought it'd be nice to know there are others that can as well. oh and my sight is perfectly fine. Thought I should put it out there just in case.