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Background

Apart from being able to sense color, cone cells are able to perceive finer detail and more rapid changes in images, because their response times to stimuli are faster than those of rods.

The fovea centralis is where cone cells are most concentrated and is responsible for sharp central vision (foveal vision), which is necessary in humans for reading, driving, and any activity where visual detail is of primary importance.

Question

It is hard to imagine what it would be like to be missing the fovea centralis, and even harder to imagine what it would be like to have one the size of the entire retina! In any case it seems that having a bigger fovea centralis would be beneficial for survival, so why do we have so much peripheral vision?

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Fovea has very high resolution , color vision but low light sensitivity. So, if we consider the fact that most mammals are nocturnal doesn't this make sense ? –  biogirl Dec 8 '13 at 4:21
    
See this –  biogirl Dec 8 '13 at 4:28

1 Answer 1

We use central vision for a lot more things today than in the past. Peripheral vision is most important in navigation, so those who lose their central field retain the ability to navigate around objects. It is important that this is fast and sensitive in the dark as well as light. It isn't important for it to be in colour; this would mean it would be less sensitive in the dark and colour isn't important in navigation and also it would take longer. Navigation is of vital importance as it can be the difference between survival or death in the flight or fight response. Similarly it is important in the fight part, being able to see a foe.

Let's our foveas were bigger, well we would lose the above. What would we gain? The ability to see more at full resolution and colour. It's impossible for us to concentrate on more than we can see in our central field already. in fact we dart our gaze around to focus on many things because we can't focus on multiple things at once. By this I mean thinking about what we see not processing it. Of course we would also require a much larger brain to be able to process it all, processing the central field takes a lot of brain matter.

So in conclusion, it's not helpful.

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