Im confuse about central fixation.Some people say to practice looking at one point best and others worst but other people say that central fixation is the result of looking in a passive way.Do we practice it or do we just let it happen as a result of relaxation?
Indeed, central fixation is a state rather than process, but you can obtain it by doing some simple things, such as looking at one point and noticing that the point you've been looking before is now seen worse. It is important not to try to see the point your are looking at best, because it is exactly what causes you strain, but do in reverse, notice the other point is seen worse. Central fixation is all about noticing the difference.
Another subtlety of central fixation is what exactly means "to see worse". I've used to over-complicate this question before, but finally concluded that it should be understood literally, just to see with less detail and with less brightness. It follows from the construction of the eye - the farther from the center of retina, the less cells there are, and they are packed with less density. It means less resolution and less light sensibility. The brain of course compensates for this effect so that people with normal sight are hardly aware of it, and think they see all at once and equally well, but by drawing their attention to the fact, they notice that too.
At first, central fixation should be practiced on the distance where you see best, i.e. close to your eyes if you are myopic. I used to underestimate this advice before and used to try to obtain central fixation on far objects, but often failed because when you don't see an object well, it's hard to see it even worse, and I didn't notice the difference. The difference in brightness is better noticed when you look on a light (such as candle or electric light) and then away from it.
The smaller is this point, the better is your vision. In fact, the size of the smallest detail you can see is equivalent to the size of your central fixation point.
The point is measured in angular units and theoretically can be as small as the angular size of a single light-sensitive cell, or even a half of it. Some people can see moons of Jupiter with naked eye, because they obtain high degrees of central fixation.
When I'm obtaining central fixation, I start with a bigger distance, e.g. first and last letters in a row on the test card, then neighbor letters, then sides of the same letter.
I can only see the sides of a letter distinctly when I can distinguish them, which is, to look at one and notice that I'm not looking at the other side. Otherwise, if I'm unable to look at one side only, it means that I see both at a time, i.e. I see blur. Central fixation is in fact very obvious and self-understood.
