How the calculators work
The transposition, Prentice's rule, vertex, meridian power, blank size, vertical imbalance, magnification and tolerance tools print the formula, the substitution and the result, not just the answer, since the method is what carries over to the exam. They and the drill generator take their arithmetic from one shared module, so a tool and a practice problem cannot disagree about the same equation.
Every calculator, guide and reference page is free, as are 10 untimed drills a day per skill. The paid tier adds unlimited drills, a timed exam mode, progress history and a downloadable formula sheet.
The tolerance tables give ANSI Z80.1 figures for finished single-vision lenses as commonly published; no edition is named, because the standard is revised, so check the edition in force where you work before applying a bracket to a real lens.
Who is behind it
One independent developer built OpticBench and runs it, together with DatumLab, PhysRef, Trigonify and TermDecode. The guides appear under the OpticBench name with no personal byline, and the structured data names the OpticBench organization as their author. No optician, optometrist or ABO certification is claimed. Each guide links the calculator it relies on, so a worked example can be re-entered and checked, and its date marks when its text last changed.
What this site is not
A study aid for optical mathematics, nothing more. It is not a prescription, a medical device or a fabrication order, and it does not replace licensed judgment, verified measurements or an ABO study course; it is a practice companion for the calculation questions inside one.
Corrections
A wrong formula, tolerance figure or guide is worth reporting at [email protected]. Data handling is covered by the privacy policy, conditions of use by the terms.