Vision is like any biometric measurement, there is a range of normal rather than one single measurement. Google says that the average height of men in 1.7meters. That does not mean that anyone who is taller or shorter is abnormal, there is a range within which most of us are. The range of spectacle free vision is described in the diagram. The numbers are the lenses needed to put the eye into “perfect” focus. Someone whose focus is at point X has a spectacle prescription of -0.50 of myopia and 0.25 of astigmatism. Wearing this weak prescription would theoretically give the person better vision but in practice it’s so weak that nobody would bother wearing such a pair of glasses. Such people regard themselves as spectacle free. Anyone whose spectacle prescription falls in the blue zone would regard themselves as spectacle free and can see the world without glasses just as well as anyone else. They can perform all visual tasks perfectly with no glasses or contacts. You will notice that there is no sharp edge to the zone but rather there is a gradual transition into the zone were glasses are necessary to see clearly. The purpose of laser refractive surgery is to move your vision from the zone where glasses are necessary into the zone of spectacle free vision. We do not need to get you to the very centre of the zone to be successful. This is where the brain comes in.
Think of good vision as 20% optics (focus) and 80% data processing.
If the visual cortex gets an image from within the zone it will process it so that it will appear to come from the very centre. That is perfect vision. The software the brain uses to analyse vision is designed to work with eyes that are focused in the spectacle free zone. Evolution demanded this. That’s why we say that glasses, and to a lesser extent contacts, do not solve the problems of ametropia. They just make it survivable. Laser refractive surgery gives you the vision nature intended you to have. Laser vision correction is not a luxury; it’s a release from a handicap, the correction of a blemish.