LensCalc: The six most important calculations for all optical retail assistants, optical dispensers or dispensing optician. Oh, and optometrists might benefit too. LensCalc includes Vertex Distance, Effective Diameter, Lensmeter Helper, Transposition, Lens Thickness Estimation and Induced Prism, in a quick & easy to use format. It also includes a progressive lens markup helper!

Vertex Distance: Enter the lens power & two vertex distances. LensCalc will give you the new power required, and tell you if the difference is significant.

Effective Diameter: Enter the Frame PD, Widest Diameter & Patient's PD. LensCalc tells you the required blank lens diameter.

Vertometer / Lensmeter Helper: Enter the two powers and the axis of the second power. LensCalc gives you the proper minus cyl form. Because sometimes those plusses and minuses are just a bit too confusing!

Transposition: Enter the lens power in plus cyl form, and LensCalc will give you the minus cyl form. Useful when you've got to deal with those dinosaur Rxs. Or, if you are a dinosaur, convert those new-fangled minus cyl prescriptions into that old favourite, plus cyls.

Induced Prism: Enter the power, decentration and direction of decentration. LensCalc tells you how much prism and the base direction. It'll also tell you the effective power of the lens in that direction, to aid with dispensing advice.

Lens Thickness: Enter power, centre/edge thickness, lens diameter and refractive index. LensCalc tells you the resulting edge or centre thickness.

So, they're all there: the six most common calculations, and designed for speed and ease of use. What an excellent idea.

Multifocal markup: Place your marked-up lens on the iPhone screen, drag the top, bottom & centre markers to the appropriate place and LensCalc tells you the optical centre height, the frame depth and the datum measurement. Use it when fitting or when checking jobs!