What Causes the "Blind Spot" in Vision?

[Suraj M]

I know that the blind spot is formed because of the optic nerve leaving the eye ball.
Consider this..
Now once your seeing through just one eye you are not able to identify a small region of your vision, so shouldn't it be just dark or black, rather you just see the surroundings as though there's nothing there its like our brain is trying to fill in the gap by feeding us false info(seeing the thinks around the missing region). How is that possible?

 

[DaveC426913]

Your brain doesn't fill in the gap, it pulls the edges of the blind spot together so you see no gap.

The thing to keep in mind is that the brain is not a faithful recorder of reality. It is designed to hide confusing, distracting things from you. You can't trust it.

Jay Ingram wrote a look called Theatre of the Mind that goes into this in great depth.

 

[DiracPool]

You can actually detect your blind spot by moving your finger around in front of your eye. There's a place you can configure it at where you are unable to see the tip of your finger. But DaveC is right, your brain compensates for this trivial biological anomaly among many others to give you a coherent picture of the world. Run a search on change blindness.

 

[Graeme M]

But given that the blind spot is off centre, is that what's really happening? You can only really see clearly in a very small circle of attention, everything else is in your peripheral vision which is not at all clear. For example staring at the screen as I type I am aware of various other elements of the screen but I cannot see them clearly - it's largely a mush of colour and shapes. If I concentrate, I can see the blind spot blotting out one of the screen buttons, but generally speaking because you aren't really paying attention to things in your peripheral vision so an area of less clarity just blurs into the background. Normally with both eyes open of course your brain actually does have info for each blind spot, it's just coming from the other eye.

 

[DiracPool]

One thing that's important to realize is that the foveal representation of the retina in your striate cortex is grossly over-represented. But we really don't notice this. Again, our brains organize these anomalies to give us a smooth perception of our environs.

 

[Graeme M]

That's really interesting - I didn't realize the brain does so much adjusting of the input.

Although on reflection that's sort of what I was driving at - the central vision component is what occupies our attention and the rest is rather more of a background noise. We interpret that as a continuity but it isn't really in some respects.