New Contact Lens Calculator

Long ago, after developing the contact lens searches for EyeDock, my next big programming project was to build a contact lens calculator. I'm embarrassed to say this, but that was nearly 15 years ago, and I hadn't really touched that calculator since.

CL calcs screenshot

Sure, contact lens calculations have changed very little in that span of time. The calculator still gives completely valid results. However, other things have changed. For one, browsers and web programming languages have grown much more powerful and are capable of so many more things. Also, to be honest, I've become a much better programmer over time and just have a better idea of the best way to do things. One of the curses of building applications is that you are your own worst critic. When you use your own products you're always seeing things you could have done better, or you wish you'd done differently.

Well, earlier this spring I decided it was time to buck up and rebuild the contact lens calculator from scratch. My main goals were as follows:

1. Give the interface a facelift. 

2. Make the fields for entering K's and refractions quicker and more flexible.

3. Add a SPE / CPE bitoric calculator (Using Tom Quinn OD's nomograms, which were also used on the GPLI calculator).

 4. Do a better job of making lens recommendations.

 5. Do a better job of explaining the calculations.

In the list above I'm most proud of item number 5. I've said on many occasions that EyeDock doesn't exist to replace thinking. The last thing I want is for people to just input numbers and blindly trust the results. This new calculator is made to "show it's work" so the practitioner can not only understand the results but make modifications if they choose to. My hope is that this will be helpful for both experienced contact lens fitting ODs as well as novices and students.

Here's a little video walkthrough of the new calculator:

EyeDock members can check it out the new calculator here.

I hope you find this useful. Once again, I'm considering it to be a beta product until you all get a chance to kick the tires a bit. As always, let me know if you run into any problems!

Your optometrist / programmer pal,


Todd M Zarwell OD FAAO

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