We often confuse sensation and perception.
From: Wikipedia.
Think of the camera obscura. There is nothing but light which is making the image on the wall. Or think of a video camera attached to a video screen. The camera captures the light external to it, turns it into data and turns that data in to the video image on the screen. It does not “think” about the image. It does not “have an opinion” of it. It simply reproduces it.
The eye does the same thing. It captures light eternal to it, turns it into data and reproduces that in your brain. Until then it does not “think” about the image. Thinking occurs after that data is received. That raw data is sensation. The processed data after reception is perception.
If you are still not convinced then this talk by Sheila Nirenberg about her research on the prothetic eye is an excellent real-world demonstration of what sensation and sense data is.
