Depending upon causes
muscular strain - Ruta 30
accomodation issues - onosmodium 30
dryness - Euphrasia 30, Puls 30
aesthanopia - jaborandi 30

lubricant eye drops like cinelube, and vitamin a supplementation helps in dryness.
usage of uv filter glasses. Washing eyes regularly with water.
reading in enough light.
using night mode in gadgets at night.
any underlying pathology must be identified if not responded to treatment within 2-3 weeks.