Office lenses: begin with your monitor distance

Define the work area

A reading distance and a screen distance demand different focusing. In a simplified optical model, the demand in dioptres is approximately one divided by distance in metres: 40 cm corresponds to 2.50 D and 80 cm to 1.25 D. These are teaching values for the task, not a prescription, because the eyes contribute accommodation and other factors matter. Office lenses allocate useful areas to near and intermediate tasks; the usable maximum distance varies with the design.

Write down the distance to each monitor, the desk and the people you speak to. Describe how often you stand or move around. A product label alone cannot describe that pattern of use.

Keep the claim proportionate

A 2018 Cochrane review found limited evidence when comparing optical interventions for computer-related symptoms. Discuss the specific viewing range of a proposed pair and its limitations, including whether it can be used for driving.

A worked example

Measure from your eyes to the screen in your normal chair position, not from the keyboard. Also note the height of the monitor and whether you use a second screen or need to recognise people across a room. A lens chosen only for reading a phone may make an elevated monitor uncomfortable. Ask the dispenser to explain the intended working range and whether a separate distance pair is needed for leaving the desk or driving.