The reason for being short or long sighted is simply to do with the physical distance between the lens of the eye and the retina/macula. The reasons why the length isnt optimal are a whole other story but once you are i that position i cant see how wearing on not wearing specs will worsen your eyes unless perhaps if you only have a very very low degree of correction an you wear specs, it makes your eye muscles lazy whereas if you dont, your eye will fight to try and correct the shortfall? im probably talking rubbish,,its just a theory..
Another point, if someone has perfect sight, is their eyeball perfectly spherical? How much does the distance between lens and retina/macula have to increase before you are aware of myopia? Whats the scale ofi t? Is it 1mm/5mm/ ?? What is the excess length from perfect vision per dioptre of myopia? or isnt it as simple as that?