Children's eyecare is of particular importance, and we're not merely being sentimental!
If you have children under the age of 7 please read on.
The retina is the photosensitive layer in the back of the eye, responsible for transferring visual information to the brain. Photoreceptors known as rods and cones collect this information and transfer this to the brain via the optic nerve.
Rods and cones vastly outnumber the fibres in the optic nerve so what happens is that a number of photoreceptors will connect to a single nerve fibre. As vision is more highly defined centrally than peripherally, a mere handful will arrange themselves per fibre in the central retina while in the peripheral retina you would find many thousands per fibre as vision here is much less defined.
To demonstrate this point:
You're reading this text and it's nice and clear. Now look up to the Eyeful Tower logo, while you are looking at it, this text will no longer be in your central vision and won't be clear enough for you to read it.
The photoreceptors and nerve fibres arrange themselves while the eye is young, and this can only happen properly if the eye is focussing clearly. If the eye isn't receiving a clear image then the photorecptors and fibres will arrange themselves evenly rather than giving preference to central vision.
It's a done deal by around the age of 7 and if the eye hasn't been seeing clearly during this time the central vision won't develop as described above. The result being that the eye will be permanently incapable of highly defined central vision.
So in a nutshell!
As an adult you can't do yourself any harm, if you need glasses, whether you wear them or not. You vision is what it is and it will do what it is going to do.
However as a child regular eye exams are imperative as is wearing any glasses which have been prescribed.