thanks. i've read up on this. is it harmful to do this? i am 30?
You are purposefully making your focusing muscles work more than you actually need up close - which is something most younger people can do if they want to - but it could give you a heachache. This is how a normal, young human eye is able to focus clearly at distance one moment then arms length another moment then very close the next. It is called visual accommodation and you can look that up for more info.
MJK MD