Eye Chart pro is a free iPad app which lets you check if your vision is good by bringing the Eye Chart used by doctors for testing your vision clarity. iPad Portability has a lot of advantages and this is one of the best use you can make. Lets say if you doubt on your kid and is complaining often for not seeing things written on blackboard at school, Eye Chart Pro can at least give you an idea if he is going to get glasses or not.
This application displays the famous Snellen Chart and you can hold it at a minimum 20 feet and ask to read the alphabets loud. Also in case if you think the person has memorized the alphabet sequence you can randomize it. There is also Visual Acuity ratio mentioned for each line that one needs to read to get if the vision is 20/20 or 20/200.