**Usage:** In addition to interactive use of the calculator, links to the calculator may contain either logMAR or Snellen values that will be automatically evaluated. To evaluate a logMAR value, add the following to the link: '

**?l=x**', where x is the logMAR value to be evaluated. For example,

this link will automatically evaluate logMAR -0.2. To evaluate a Snellen value, you may provide just a denominator (sd), or both a numerator (sn) and denominator. If only a denominator is provided, the numerator is assumed to be 20. For example,

this link will evaluate 6/12.