Can I make my own bloodshot eye reliever?

I bought a little bottle of Visine the other day to clear up my bloodshot eyes. Now I must say that the stuff worked like a charm, perfectly clear eyes almost instantly. The only thing I disliked about the product was that it had written on the bottle “Discard 4 weeks after opening”. There is no way I would use the whole bottle within 4 weeks and Im not going to buy a new one every month so I wanted to know if I can make my own at home.

Visines’ webpage lists the active ingredient as
**Tetrahydrozoline Hydrochloride 0.05%. **

So what is this ingredient and can I make this product at home?