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Utterly Awe-inspiring Bio-mechanism behind the Blink of an Eye

posted Apr 10, 2012, 7:14 PM by Pratik Panchal   [ updated Apr 10, 2012, 11:29 PM ]
9th April, 2012, @lab, Phillips Hall.

The other day, over some project work, Skye N. came over and bumped me with a question: "Why don't we feel our eye-blink?". 

"What do you mean by why don't we feel it? Obviously we feel it, see <blink> <blink> <blink>", said I with utter naivety. 

"No, that is what you feel when you blink your eyes consciously. What I mean is, why don't we feel it when we are not paying attention to that process, which happens continuously with such 'high' frequency?"

"Well, maybe we are not paying attention to it. Maybe, the brain is occupied with other activities and so doesn't notice this reflex."

"So, you mean to tell that if we 'blink' (switch-on - switch-off) the lights of the room for the duration of time it takes for the eye to blink, the brain wouldn't notice it?"

"I guess so - Well, lets try it."

So, over next hour, I spent finding out the duration of the eye-blink. I kept a light sensor near to my eye, which sensed the reflected light from my eye. I expected that when the eye-lid would close, the photo-sensor output might go low since its not getting as much reflected light as it got from shiny surface of my eye-ball. But to vain, it did pick up reflections from my eye-lid and didn't operate as I intended. So, I took a black marker and painted the eye-lid with it. Problem solved. No more reflections from eye-lid.

The oscilloscope said that the duration was about 310 milli seconds at about very 15 seconds. Well, I could have got this values through Google, but its interesting to get your "own" readings sometime.


So, the next step was writing a small code and deploying on a PIC18F4420 which would shut down all the lights of my room every 15 seconds for duration of 310 ms, and well that was pretty simple.

Well, this frequent 'blinking' became extremely annoying and frustrating. I couldn't comprehend why the same equivalent action wasn't so disturbing. The natural eye-blink goes almost unnoticed untill you do it consciously.

The awesomeness behind:
It turns out that when the eye blinks, the part of the brain which receives the visual signals from eye-balls and processes them, also shuts down for those 310 milli seconds of duration. Thus, the brain doesn't see a black dark patch for that duration, instead, it just 'skips' those 310 ms, unless and untill you consciously blink your eye which keeps that part of brain active and enables you to see that black dark patch for the duration of eye blink. A more biologically technical description can be found here: http://phys.org/news5431.html

This is something like an 'interrupt' routine of a processor; the processor will execute the task only when it receives the 'interrupt' signal to do so; else it simply doesn't acknowledges it. Well, in this case it is done to free up the processing space.

Isn't this simply awe-inspiring mechanism? Its such an elegant design! Such simple yet absolutely smart bio-mechanism deserves a moment of attention. It naturally leads us to think the complex behavior of the evolutionary path that we have been from. What a wonder, these carbon and hydrogen atoms can do when they are left for 13.7 billion years (the life of the universe)!!


P.S.: Please don't paint your eye-lid with a marker; It takes two days to get off  :)

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