Differentials
Differentials are reduced glasses for close up activity. They have a lower correction than your normalized lenses that allows you to see clearly only up to the screen. The difference between normalized and differential lenses is usually between 1 and 2 diopters.[1][2]
Why are differentials worn?
The primary stimulus for axial elongation of the eyeball is hyperopic defocus, which occurs when someone:
- Is engaged in close-up activity
- Wears more correction than they need to when seeing the object that is close up.
Differentials allow the wearer to wear just what they need to, to see up close. This removes the stimulus of hyperopic defocus, and stops eyes from getting more myopic. In a sense, it's a quick fix. 
It's fairly easy to stop myopia from progressing, just by wearing differentials. The axial length of the eye does not randomly change by itself, it only increases in response to stimulus.
References
- ↑ The EndMyopia Blog, https://endmyopia.org/faq-items/what-is-the-differential-prescription/
- ↑ {{cite jake|https://endmyopia.org/choose-reduced-glasses-prescription-differential-close-friendly-glasses/%7CHow To Choose A Reduced Glasses Prescription (Differential / Close-Up Friendly Glasses)