App Review: Crossed Cylinders

"Crossed Cylinders makes adding cylindrical lenses easy." says the blurb on the app store page, but does it? Find out in this edition of App Review.
Crossed Cylinders is a little app (both in popularity and size, weighing in at a piddling 0.1MB) developed by Diffraction Limited Design and released way back in 2008.

The premise is simple, enter your refraction in whichever form you like and the app will tell you all you need to know. This is remarkably useful for optometrists who do a lot of over-refraction. As you can see in the screenshot the facility to enter old rx and over-refraction makes what could be a fairly irritating piece of arithmetic in a busy clinic, something of a breeze.

 Overall the user interface is kept functional and the results section is very clearly laid out. Data entry for dioptric power is performed through either typing in the values or by using a slider. The system can handle +9.00 to -9.00 on the spherical component and +6.00 to -6.00 on the cylindrical. Axis entry is slightly different as it has small arrows, making one degree changes. This functionality is well thought out, making for simple fine tuning adjustments to axis after speeding along with the slider. Axis value is slightly out allowing the user to put in an entry of 0 as a degree, but it does auto-correct this on the results, making this a minor irritation at best.

Results are clearly displayed in both negative and positive cyl forms at the bottom of the screen. Ordinarily these show in raw arithmetic mode, ie allow from any digit not just 0.25 stepped results. There is a toggle switch which turns on rounding should you want this taken care of automatically. Next to the toggle switch there is a clear everything button, something very useful for a calculator application, but a function which is often overlooked.

Overall this is a well made, simple utility app which will vary in usefulness depending on your particular clinic scenarios. At £2.49/$3.99 how much you would benefit from this tool is something well worth considering before making a purchase.

Crossed Cylinders is available now from the App Store for £2.49