Verification tests are used as a way to make sure the user is not a bot. Or for insurance or fraud reasons (We use them for bots). As most bots cant figure out the way to trick this system (Thanks to Kevins leet coding). As for "Visually Impaired" people they will just have to do just as stated:
was told if I could not read it, to contact an administrator.
And the Admins will by-pass the code and grant them access or if it is a suspicious account then they will send them a Hearing test. After that they will be able to be an normal member.
As for insurance reasons this is for thinking like banks to stop them from getting sued by someone who cant see what they are reading. For example Jon Doe cant read print below 18 and he clicks a wrong box that says "Send 100 dollars to client" in his checking/billing account and then trys to sue them for lost money. So the bank says look you took this test when you joined our butts are covered.
~Hells