Interacting with a computer calls for concentration, and the sustained stress tends to fix vision in a stare. As blinking decreases, the eye muscles have difficulty focusing. Users also tend to hold their breath when trying to see the screen better. This decreases blood circulation and increases bodily tension. The resulting strain eventually leads to refractive error, most often chronic myopia.
Lenses are symbols of modern civilization.
The human eye evolved naturally to focus on distant objects. Looking into the distance, the internal eye muscles relax. Close-up work, on the contrary, causes the eye muscles to reshape the cornea. Protracted close work strains the eye muscles. If the eye strains sufficiently, the muscles undergo spasm, which then changes the actual shape of the eye.