Parks Three Step Tool improvements

Just a quick post to make you aware that I’ve uploaded a new version of the Parks Three Step tool.

It works the same as always - just answer the three questions to establish which EOM is to blame for acquired vertical diplopia.

So what’s changed?

Eom parks three step explanation

Instead of just taking your input and spitting out an answer it now takes a “show your work” approach. For each of the three steps the tool will 

  1. Explain which muscles are suspected based on your observations of the patient.
  2. Show an illustration of #1


I’ve never been very keen on the idea of trusting a computer to make my clinical decisions. On the other hand, I don’t do the Parks Three Step test very often, and thinking through what each step means when I have a patient in my chair can be a bit taxing. Ideally, I’d like my the tools and calculators I create for EyeDock to make your clinical decision making easier, but I don’t want them to be a replacement for your thinking or common sense.

Hopefully this new version will strike the balance of being useful but also educational.

As an aside, this is why I decided to display optical crosses in the oblique cross cylinder calculator and outlined exactly how the contact lens calculations are done.

- Todd

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