Pair of Apple patent applications describe partial display updates for VR and AR headsets

It is advised that for each time a display updates, the circuitry inside the display will adjust every pixel in an LED or OLED panel to match the new image. As some displays have higher and higher resolutions, and in some cases a need to operate at high refresh rates, these situations can sometimes lead to unwanted artifacts appearing on the display, ruining the image.

https://www.blog.michiganfreelisting.com/pair-of-apple-patent-applications-describe-partial-display-updates-for-vr-and-ar-headsets/