Vatji the peripheral vision is made up of cones and rods. Focus is with the fovea which is a area of densely packed cones. This is the part of the eye that normally focuses on reading.
I feel it should also be mentioned that in reality, we are only ever seeing a "sharp focus" a tiny portion of the time. The eyes actually work to create a fully whole, detailed image by numerous automatic eye movements called saccades. The fovea is an insignificant portion of your whole eye. Most of what you perceive is actually delayed by the true mechanisms of perception, as well as actual cognition. When you're highly intoxicated from alcohol, saccade activity actually slows down, which is what creates a single point of sharpness surrounded by blurriness.
If you really dive into the heart of PhotoReading, you learn there's actually more than one way to do this thing called "PhotoFocus." The important concept behind it is simply than you're removing conscious interference and inputting whatever visual stimulus is in front of you only into subconscious processing.
