ABO and NCLE exam math practice
Optical math, drilled until it is automatic
OpticBench is a free trainer for the calculations opticianry students meet on the ABO exam and at the bench: transposition, Prentice's rule, vertex compensation, blank sizing, tolerance checking, and vertical imbalance. Every skill pairs a calculator that shows its work with an unlimited generator of practice problems, each graded exactly and explained step by step. Everything runs in your browser; nothing you enter leaves it.
Rx transposition
Convert between minus-cylinder and plus-cylinder form with the steps written out.
Prentice's rule
Prism from decentration: P = c x F with the correct meridian power and base direction.
Vertex compensation
Effective power when a lens moves toward or away from the eye, both directions.
Minimum blank size
ED + 2 x decentration + allowance from frame A, DBL, and the patient PD.
ANSI tolerance checker
Ordered against measured, per parameter, with the axis table applied for you.
Vertical imbalance
Per-eye Prentice prism at the reading level and when slab-off enters the picture.
Meridian power
F = S + C x sin^2(theta - axis) with a lensometer dial and power cross.
Spectacle magnification
The power-factor approximation: how much larger or smaller the retinal image gets.
Learn the why, not just the answer
The guides walk each formula from first principles with the canonical exam examples: transposing -2.00 -1.50 x 180 into -3.50 +1.50 x 090, why a +10.00 D lens at a 12 mm vertex needs +11.36 D at the cornea, and how a lensometer presents the two principal meridians. The reference section keeps the formula sheet, the ANSI axis table, and common vertex distances one tap away.
Frequently asked questions
What is OpticBench?
OpticBench is a free browser-based trainer for the math opticianry students meet on the ABO exam and at the dispensing bench: Rx transposition, Prentice's rule, vertex compensation, meridian power, minimum blank size, tolerance checking, and vertical imbalance. Every tool pairs a calculator with worked steps and an unlimited practice-problem generator.
Is OpticBench free to use?
Every calculator, guide, and reference page is free with no account. The practice generators include a free daily drill allowance per skill; the calculators themselves are never limited.
Does OpticBench replace an ABO study course?
No. It is a practice companion for the calculation questions. Use it alongside a full course or textbook that covers theory, materials, standards, and dispensing procedure.
Is anything I enter uploaded anywhere?
No. All calculations run in your browser and practice progress is stored on your device only.