Lens Calc - Optical Dispensing2.5 - App Store

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!

Version History Bug fix for effective diameter screen. 2.5 07/27/2025 Updated to work with modern devices.
Fixed bug with Vertex Distance screen. 2.4 07/24/2025 Version 2.3:
Oh dear. Version 2.1 had more bugs in it than an entomologist's office. Sorry about that.
This version fixes the inability to even use the Effective Diameter tab.

For 2.2:
Fixed bugs on the Vertex Distance page which kept flipping around the vertex of Rx and specs values. Also fixed the precision value not being remembered.
Also the plus cyl form switch on the power entry screen was messing up the cyl power.

For 2.1:
Fixed bugs on lens thickness page which always showed "edge thickness" even for a minus lens, and only allowed 1 decimal point for the refractive index.
Also updated to work well with iOS 15.

If you want new features or calculations, don't hesitate to contact me! 2.3 06/04/2022 For 2.2:
Fixed bugs on the Vertex Distance page which kept flipping around the vertex of Rx and specs values. Also fixed the precision value not being remembered.
Also the plus cyl form switch on the power entry screen was messing up the cyl power.

For 2.1:
Fixed bugs on lens thickness page which always showed "edge thickness" even for a minus lens, and only allowed 1 decimal point for the refractive index.
Also updated to work well with iOS 15.

If you want new features or calculations, don't hesitate to contact me! 2.2 05/29/2022 Fixed bugs on lens thickness page which always showed "edge thickness" even for a minus lens, and only allowed 1 decimal point for the refractive index.

Also updated to work well with iOS 15.

If you want new features, don't hesitate to contact me! 2.1 05/26/2022 - Added support for iOS 13 including Dark Mode.
- Updated some icons. 2.0 06/11/2020 - Fix for crash on iOS 7
- Fix for number conversion error on non-English locales.

Also from 1.51:
- Updated for iPhone 6 and 6 Plus screen sizes.
- New orange and purple colour scheme! Pretty! 1.52 11/07/2014 - Updated for iPhone 6 and 6 Plus screen sizes.
- New orange and purple colour scheme! Pretty! 1.51 10/08/2014 Updated for iOS 7, just in time for iOS 8... 1.5 08/20/2014 - Added precision option to vertex distance calculations
- Fixed script entry display on iPhone 4 1.4 12/21/2010 - Fixes bug in multifocal markup screen on iPhone 4 1.3 09/08/2010 - Support for OS 4.0
- Bug fixes

- Added lens thickness calculation

- Added multifocal markup checker

Lens thickness calculation uses the approximate sag method to determine centre or edge thickness of lenses. Please note that this gives an indicative value only, and should not be taken as accurate.

The multifocal markup allows you to measure the heights of a multifocal once its dotted up. 1.2 06/30/2010 - Significantly improved Vertometer calculator. Now much easier to enter the powers! 1.1 03/11/2010 1.0 03/05/2010