This is one question on d lips of most spectacle/contact lens wearers. The truth is this notion has nothing to do with education as even professors, judges even foreigners (I have been opportuned to treat) end up expressing this fear. They'ld often say:
I used to see without glasses but since I started using glasses I can't see like I used to with my eyes.
Well if u have this notion, u are not alone. Besides, the fact that a notion is popular/widely accepted does not make it true!
Now let's understand how our spectacle lenses work:

The human eye has its own biological lens which cetaris paribus should be able to resolve both near and distant images clearly and bring them to focus on the retina which as you know is the centre of vision. Now recall the definition of myopia or any refractive error focuses on the inability of the visual system to bring an image to focus on the retina. In some cases the biological lens seem to posses a very high converging power which brings the image to focus in front of the retina, thus we introduce a diverging or a minus lens to reduce this power and bring the image to focus on the retina! All your spectacle lens does in lay man's term is to artificially help your biological lens!

Does it tamper with any ocular tissue?
NO, it only creates a virtual image (image formed by a diverging lens is virtual) that falls on the retina.

Why does my vision feel worse, when I take off my lenses?
This feeling is PURELY PSYCHOLOGICAL, you really can't remember how hard you used to squint before you got your lenses! One way to find out, each time you go for visual checkup (recommended every six months) try to read the chart with ur eyes and ALWAYS note where you stop.

NB: Some conditions such as presbyopia and progressive myopia are actually PROGRESSIVE in nature and as such your vision worsens with or without glasses. Also pathologies and degenerative conditions worsen vision with or without glasses.

Glasses do not improve vision. I have been wearing glasses since 2004 till now and I can say that there is no improvement, the eyes are just like they were when I started to wear glasses initially, The question of when I am going to drop it has plagued me for long but deep down I know I have to manage my eyes as they are for eternity.

Obinnau:
Glasses do not improve vision. I have been wearing glasses since 2004 till now and I can say that there is no improvement, the eyes are just like they were when I started to wear glasses initially, The question of when I am going to drop it has plagued me for long but deep down I know I have to manage my eyes as they are for eternity.

That is not entirely true, but conditions vary, u can get contact lenses to get a natural feel anyways.