Question
I was just wondering if you can tell me what the standard is that a prescription is allowed to be off and is it for a single number or for each number in the script. Additionally how is it that different places can read the same glasses as almost completely different prescriptions.
Answer
Dear Brian,
I have not completely understood the Q.
The standard is a chart either a Snellens chart or some other form of Visual acuity chart which is kept at specific distances.
hence the numbers SHOULD be the same wherever you test, unless being done on what is like a computer where the results are not constant but variable.
Hope this is what you meant???
Regards,
Dr Shroff
