Tuesday, September 2, 2014
Eye and Vision Care
What line in the Snellen Chart can normal eyes see? Does it mean that you need to be able to read all the lines on the Snellen Chart correctly to be considered as having good eyes or there is a range in lines for good vision? What is the lines that tells a person that his eyes is not good if he cannot see the letter in that line? If the person can read all the lines in the chart with some mistakes (eg. read incorrectly some letter in the lines) does it mean that he has bad vision too?
Like blood pressure, heart rate and other metrics, there is a range of vision that can be considered normal. We talk about 20/20 vision, but many patients can see better than 20/20. Even if a patient doesn't see 20/20, their vision can still be considered normal. All US States have a vision criterion for an unrestricted driving license. This is usually 20/40 which implies the ability to see letters twice as large as the 20/20 line.
Finally, most letter charts contain lines of letters too small for anyone to see at the standard distance.
Ask your doctor how good your vision is. He or she will tell you.
Mark Bullimore, MCOptom, PhD
College of Optometry
The Ohio State University