Opterio

Opterio works the optics math on the ABO and NCLE optician exams, one step at a time. Ask about a prescription or a frame and Opterio runs the calculation, shows every step, points out the trap the exam likes to set, and rounds to the nearest quarter diopter where that matters.

Twelve calculators:

• Transposition: move a prescription between plus- and minus-cylinder form.
• Spherical equivalent: sphere plus half the cylinder, naming both quarter steps when the result lands halfway.
• Vertex distance: compensate a prescription for a change in vertex distance, one meridian at a time, for example from glasses to contact lenses.
• Prentice's rule: induced prism and its base direction when the eye looks away from the optical center, for spheres and sphero-cylinders.
• Lens thickness: edge or center thickness from power, index and diameter, compared across common lens materials.
• Minimum blank size: the smallest lens blank a frame needs, from its effective diameter, eye size, bridge and the patient's PD.
• Base curve: Vogel's estimate of the front curve for a prescription, halving the spherical equivalent first for a minus lens.
• Lens power: the power from the front and back curves, with back vertex power for a thick lens and lens clock readings converted for the material.
• Prism resolver: horizontal and vertical prism combined into one resultant prism in 360-degree notation, or one prism split back into its parts.
• RGP fitting: a GP contact lens power from the K readings, the glasses prescription and the base curve, with the tear lens and any residual astigmatism.
• Near PD: the reading PD from the distance PD and the reading distance, with the three-quarter rule.
• Effective diameter: twice the longest radius from the boxing center, or an estimate from the frame box and how rounded the corners are.

Every answer comes with a card that shows the result and the working. Open it full screen to change any number and watch the answer update, see the diagram, and try an exam-style practice problem. Answers come in English, Spanish, French, Chinese, Tagalog, Vietnamese or Korean, following the language you write in.

Opterio is for study and for checking your own working. It isn't a prescribing tool and doesn't replace a clinician's judgment.

There's no account to create, and the calculators don't save what you enter.