The lenses contain three strengths in one, which allow you to go from reading to working on your computer, and then to interacting with others close to you
Multi Focus reading glasses feature three strengths in one lens- the bottom third has the highest strength (and the power you choose) for reading
The middle third has a slightly reduced magnification for computer use, and the top third has about half the strength of the bottom, for clarity when interacting with someone nearby (sitting across a desk, for example)