system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't we read text unless we look directly at it?

For text that is more than about a meter away from our eyes, we can't really read it without focusing on it. If you look just a tiny bit above the text, it just looks like a bunch of jumbled letters. Why?
gpt
The eye senses light using 2 types of cells, rods and cones.  Rods are highly sensitive to light, but can't see color and deactivate when there's enough light for cones to work.  Cones aren't as sensitive, but can see color and work in bright light.  There's an area in the center of your eye called the fovea, where you have the highest concentration of cones for easily seeing details in well-lit areas.  Through the rest of the eye, you have fewer cones, so you can't see the details of the letters that you need to read.