The white chart with the big black E at the top and lines of letters that become increasingly smaller. The Snellen Test is one of many tests used to determine visual acuity. The term 20/20 means that the patient can see an item 20 feet away with the same clarity that a normally sighted person can see an item 20 feet away. 20/40 means that the patient can see an item 20 feet away with the clarity that a normally sighted person can see an item 40 feet away. This is worse than normal vision. 20/10 means that the patient can see an item 20 feet away with the same clarity that a normally sighted person can see an item 10 feet away. 20/10 is better than normal vision.