troyvit

It doesn’t take much to prove that computers are idiots, but most captchas go too far. Captchas based on graphics don’t work with blind people yet they dominate comment forums. This is a logical captcha that uses math and simple riddles to weed out the machines. This plugin comes with 10 predefined questions and the ability to add more. The math part isn’t too hard and can be disabled if you’re dealing with people who don’t like math. This plugin relies on php sessions to store information.

Text Captcha

Text Captcha uses riddles and math to make sure your posters are real instead of computers.

Petroit

Blindfriendly Admin is a plugin for blind and purblind administrators of WordPress. It enhances overall accessibility of admin area and tries to be more blind friendly. 
It can also remove any menu items so your screen reader does not read again and again menu items you don’t use. 
Also plugin adds option to hear sound after click. This is of course optional and can be turned off.

Blindfriendly Admin

Plugin for blind and purblind administrators of WordPress.

Text Captcha vs Blindfriendly Admin