I've been told that too-tight contacts can cause otherwise-symptomless
corneal damage -- how do you know whether your choice is too tight or not?

My 89-year-old MIL had terrible circulation (her feet were dark purple and
the skin was frighteningly thin) and with MD was unable to actually see her
feet, much less bend over to cut her own gnarly toenails.  Manicurists
refused to even touch her feet for fear of damaging them (as would I), much
less try to trim the nails.  In her case there was no other option, and the
cost was entirely justified.

The first podiatrist she tried made her cry from the pain, and the bitch
just told her to suck it up.  The second one was very gentle and was willing
to give her topicals if she needed them -- which she didn't.  Good guy.

A friend filled a prescription for 2.5x-strength naproxen, even though she
gave me a couple of big bottles of Aleve (good stuff!) after her mom died.
Go figure.

I have mixed feelings.  There is a podiatrist who visits my father's
Home.  He gets a bunch of money for trimming toenails.  It's all charged
to Medicare.  He wants my dad to get surgery.  My sister takes him in to
a doctor.  The doctor is not happy.  My dad has one kidney.  It barely
works.  He is diabetic.  He has no feeling in his feet.  He is 90.  He
has no problems with his feet other than needing the corns filed off.  
He is not a candidate for this surgery.  

Things are weird.  I shared an office for five years with a woman who's
father was a pharmacist.  They had prescription aspirin.  The tens
require a prescription.  Of course, you can just take two fives.  No
prescription.

Still, I'm going to see the OD.  If I had to pay for it, I might think
twice about it.

I can see why prescriptions are required for drugs, because those can
be easily abused or sold in the black market. But to me, eye
prescriptions don't seem that critical.

My analogy is shoes. You could probably mess up your
feet/knees/legs/back by wearing the wrong size or type of shoes, or
improper inserts long term. Yet a shoe prescription from a podiatrist
is not required for people to buy shoes.

Of course, everyone should get an initial refraction done
professionally. But what's wrong with buying disposable contacts that
are a little higher or lower than your prescription to see how they
perform? You're not going to be seriously injured. Maybe get some
headaches or eyestrain, that's all. And if you do have problems, then
go see the optometrist (just like you'd see a podiatrist if shoes were
giving you problems).