Visual acuity produced by AR headsets can be calculated based on pixels per degree. It is the number of pixels per degree it present to the eye, the number of pixels in the horizontal display line has to be divided by the horizontal field of view provided by the optics of the headset (lens). E.g. In a display with 1280 x 800 px, the pixels per eye are 640 x 800 px, and with a FOV of 90 degrees the PPD comes out to be 7.1 (640/90). This is way too low as compared to the retina resolution of the eye, the PPD of the human fovea is approximately 60 PPD. A lower pixel density can cause blurring of text, pixelation and screen door effect (the visible fine lines between pixels on a display when seen up close). Assuming the optics is perfect, the current headsets are in the range of 20/80 which is low in comparison to a human eye. Additionally, the magnification of the optics (in some cases) is never perfect, so there is a reduction in actual PPD which further reduces the acuity.