I bought some cheap prescription[1] glasses ($20) just for computer use. They put optical infinity at around the distance to my monitor (~60 cm)[2], which keeps my ciliary muscles fully relaxed. It's completely fixed the soreness I'd feel in my eyes at the end of the day. I highly recommend it.

[1]: For those wondering, the calculation for required SPH is your_prescribed_SPH + (1/desired_distance). If you don't already wear glasses, then it's just (1/desired_distance).