Why Does My Vision Fade When I Stare At An Object For An Extended Period Of Time?

Question

For example; I tried to work on concentrating on a single spot for 30 or more seconds and after about that length of time, I notice that my vision (both peripheral and direct) begins to fade until I move my eyes again. I did this in an attempt to maybe make my peripheral vision and my focus better. I don't have trouble using my peripheral or regular vision normally, but every time I try to observe my surroundings while focusing on a chosen spot for a long enough time period, it just seems like everything becomes a blind spot.

And some personal info on my eyes: The last time I had them checked (about 4 years ago), I had 20/20 vision and I haven't noticed any decrease in vision since. I have protanomalia (mild color blindness with red and green). I also have light blue eyes; I read somewhere that eye color affects light absorption because of the different levels of melatonin. And, every now and then, my eyes decide to be very sensitive to sunlight, to the point of me being unable to keep them open without the help of sunglasses.

Is the whole vision fading thing something that happens to everyone when focusing on a spot for an extended period of time, or is it something I should get checked out?

Answer 1

It's quite normal, but most people find it easier to do with one eye rather than binocularly.

Non-intuitive though it is, the eye sees because it is vibrating, and the eye/brain system is set up to ignore images on the retina that are static. (See "Stabilized retinal image"* URL below)  Under normal circumstances this is a useful effect because allows the "filtering out" of shadows due to the internal structure of the eye.

With a high level of concentration on a single small object, that microscopic tremor can almost cease, and the brain then rapidly starts to ignore the light falling on the retina.  The very central area is the least affected though in theory, and in certain experiments, the whole world can be made to disappear.

*Both Google and the Y!A spell checker consider stabilised wrong.

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