1.3m: Clear vision at desk level. For example, a person who spend most of their time viewing monitors and working desk.
2m: Clear vision at desk level to small size room. For example, a person who utilize monitors and need to view another person for conversation.
4m: Clear vision at desk level to room size space. Presbyopes who work in a larger space. For example, a person who utilize monitors, view another person for conversation and move around wordspace.
