Question about Eyes, the Brain, and Reading

In this thread heavyarms553 mentions “Without the occipital lobe, your brain can’t understand the information it receives.”

Maybe that somehow deals with this question that I’ve had for quite a while. Why can you not read in your peripheral vision?

Now, I know about the fovea and how it has a greater density of receptors and has most of the color receptors. Outside of this you can still “see” with your peripheral vision although it is not as sharp. But I think there is some kind of brain interpretation problem going on here.

If I put a printed word in my peripheral vision, I can’t read it. I find it almost impossible to make out the letters. Of course, I make sure it is large print so that even though I do not have sharp vision there, I should still be able to make out the shapes of the letters and turn that into a word. It does not matter how big the print is or how close I hold it, my peripheral vision seems incapable of recognizing the shapes and orienting them in a fashion that makes sense to me.

This very much sounds like a brain thing, not an eye thing. Does anyone have any details on this?

This is not entirely correct. Patients with large central scars on the retina are capable of using their peripheral vision to read so long as text is adequately magnified. Sometimes it takes more practice than you, a normally sighted person, would have if you simply tried it out one time. Chances are the text you are looking at is simply not large enough for this to work; the visual acuity of the periphery is decreased, so text must be made correspondingly larger in order to be read via peripheral vision.

There is one aspect of the brain/eye connection that may interfere with using peripheral vision – the fovea is not just the area of greatest resolution, it’s also the area the brain interprets as “straight ahead.” Tell a patient with a large macular scar to read text and he or she will first attempt to use the scarred macular area before the healthy peripheral area. This will obviously make reading, which is a complex oculomotor activity involving saccades and fixations, more difficult.

Yes, and I strongly suspect that when Hermitian tries to see if s/he can read something in peripheral vision, s/he is fixating, i.e. staring straight ahead, keeping the eyes as still as possible. A person with healthy eyes who did not do this would find it very difficult to avoid occasionally foveating (i.e., looking more or less straight at) the writing, but the effort of holding the eyes still is going to interfere with the normal eye movements involved in normal reading. Also, for much the same reason, Hermitian is probably trying to read stuff in the far periphery, where the resolving power of the retina is a lot worse than it is in the near periphery, just a little way off the fovea.

The person with the scarred fovea is not going to have these particular problems. They are not actively trying not to look directly at the writing, so they can move their eyes in the way that they find most advantageous, and can use the near periphery of their retinas without fear that they will accidentally “cheat” and use their fovea after all.

(Sorry about the unisex pronouns, but it is often very difficult to know what sex a poster here actually is.)

A simple experiment shows just how bad your peripheral vision actually is – take a card at random, hold it out way to the edge of your field of vision, and gradually bring it nearer, all the while looking straight ahead. Note when you can identify colour, suit, whether it’s a picture or a number, and what exactly it shows.

The reason our field of vision doesn’t seem blurry except for a very narrow, sharp centre point is twofold: first, the eyes constantly dart around in quick, unconscious movements called saccades, bringing into focus areas of your view field without you consciously directing your attention to them; second, and more importantly, there’s noone there to complain about a dearth of visual data coming from the parts of the retina responsible for peripheral vision. Something seems blurry to us if, when we focus our attention on it, we can’t resolve it as well as we’re used to; but, in the peripheral areas, being unable to resolve it well is the norm, so nothing seems amiss to us.

It’s similar to how you don’t notice the blind spot; it’s not so much that the mind does any sort of sophisticated filling in, it’s just that nobody notices anything is missing. ‘Seeing’ any kind of dark spot in that place would be a representation of absence of visual data in that field, and seeing blurriness would be a representation of a loss of quality in the data received; but that would only make sense if usually, the data were of better quality (or there in the first place). Since that’s not the case, there is simply an absence of representation, not a representation of absence.

It’s probably not that bad in the case of a poster named Hermitian – even if you invert all the gender pronouns, they’d just have to mirror themselves on their main diagonal, and everything would come out right again.