I have had glasses since I was about 12 years old. I am nearsighted. I would have to say get bi-focals if your eyes are straining now i know from personal experience the headaches can suck. I was i think 20/18 or vice versa and glasses completely eliminated all problems I was having. Alot of the bifocals have seemless design so you can not even tell they are bifocals. Just my two cents.
Hope it helps