Launched an eyeglass prescription transposition explorer for plus-cylinder, minus-cylinder, spherical equivalent, and optical-cross checks
Searches for prescription transposition calculator, plus cylinder to minus cylinder conversion, minus cylinder to plus cylinder conversion, and spherical equivalent calculator usually land on a tiny form with one answer line. That is useful, but it leaves out the part optical students and lab staff actually need to trust the result: why the new notation is equivalent.
The new eyeglass prescription transposition explorer keeps the arithmetic instant but adds the missing visual proof. You enter sphere, cylinder magnitude, axis, and whether the starting form is written in plus or minus cylinder. The page then renders the transposed prescription, the spherical equivalent, and both principal meridian powers as an optical cross.
That optical-cross view is the differentiator. A transposed prescription should keep the same power in the axis meridian and the perpendicular meridian even though the written sphere, cylinder sign, and axis change. Showing both notations side by side makes it much easier to catch mistakes than a one-line converter that expects the user to trust the output blindly.
The next-best optical candidates were a diopter and working-distance explorer for magnifiers and a binocular low-light comparator. Both are still good ideas, but the transposition page won because the search intent is more obvious and the current result set is weaker: lots of calculators, not many pages that actually explain the equivalence well.
This belongs to the Optical tools niche from the inventory and leans on the Explorer and Interactive explainer themes. It also adds variety after recent lawncare and beach-safety launches by moving back into a technical optical workflow rather than another household planning page.
It is not a spacing or layout calculator in disguise. The useful work here is preserving lens power across notation systems and making the meridian logic visible enough that someone learning transposition can sanity-check themselves.
For the formulas, I cross-checked the standard transposition rules and spherical-equivalent definition against current optical training references before shipping. The page is educational rather than prescriptive: it helps interpret or restate an existing spectacle prescription, not generate a new one.
Ideas not chosen today were the diopter-distance explorer and the binocular low-light comparator. The diopter page is still promising for magnifiers, loupes, and close-up filters, and the binocular one could make a strong hybrid buyer's guide later.