Ever wonder why that person with -12 always said that she need her glasses all the time? Even for reading? Well, we know that -12 is bad for myopia. Every literature put it as high myopia. And if those with -3.5 myopia also complain that she need her glasses all the time, of course -12 will need it even worse, right?
Well, the pictures below will put things into perspective. The first picture is someone with -3.5 myopia reading a magazine. On the left side is vision through glasses. It is sharper than the right side without glasses. While it is impossible to read the smaller print, the larger print is pretty much readable with some difficulty.
The picture below is the same magazine, but from the point of view of someone with -12 myopia. It is impossible to read anything without glasses, even the large print on the right side. Texts are just black smears. But surprisingly, even the text on the left is much harder to read. It is smaller, distorted and also have some color fringe.
Thankfully, the brain of -12 adjust from those distortion and color fringe, having to adapt of wearing glasses for long time. However the brain can only adapt to the blur for so much, and -12 blur is definitely too much to adapt.