It's hard to for my eyes to focus as well. Hard to see things.
Answer - Founder + Owner of ONA.life
Eyes getting tired is a side effect from smoking. It can be red eyes, itchy eyes, tired eyes - few different things can happen. I would recommend getting some "water eye drops" and dropping them into your eyes after you smoke. That should help.
"THC lowers blood pressure, which in turn causes blood vessels and capillaries to dilate. The ocular capillaries dilate, which increases the flow of blood to the eyes and reduces intraocular pressure. Increased blood flow creates the redness & dryness": https://www.leafly.com/news/cannabis-101/why-does-smoking-weed-make-your-eyes-red
I hope this was helpful!