# Parks Three Step

> Medical app for identifying paretic muscles in vertical diplopia using Park's Three-Step Test. (iPhone/iPad app by Todd Zarwell.)

- Source: https://appshunter.io/ios/app/parks-three-step/id858953524 (this page in markdown: same URL + `.md`)
- Developer: [Todd Zarwell](https://appshunter.io/developer/354889494)
- Category: Medical
- Price: Free
- Rating: 5.00/5 from 8 App Store ratings · 4 written reviews indexed
- Age rating: 4+
- Requires: iOS 8.0 · 5 MB
- Languages: English
- Released: 2014-04-29
- Data updated: 2026-06-10
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/parks-three-step/id858953524/reviews.md

## What is Parks Three Step?

The Park's Three-Step Test is used to isolate the paretic muscle in acquired vertical diplopia. 

Enter your observations for each of the three tests and the app will suggest which EOM is underacting. 

However, I firmly believe you should never fully trust an app to make your clinical decisions! This app explains how the each test is used to determine the final result. Consequently, this application is not only clinically useful but also helps you understand which are the primary EOMs in different fields of gaze.

## Key features

- Park's Three-Step Test implementation
- Identifies paretic muscles in vertical diplopia
- Explains test methodology
- Suggests underacting EOM
- Educational tool for understanding EOMs

## Recent user reviews (4 of 4)

All indexed reviews: https://appshunter.io/ios/app/parks-three-step/id858953524/reviews.md

### 5/5 — Fernando Aguilera MD

*2019-12-19, version 1.01*

Being a Strabismus Sub especialist for 30 years it is wonderful to see this app that takes the guess out of most vertical deviations, especially IV nerve palsy that are difficult to diagnose for the non Strabismus Surgeon
Congratulations !

### 5/5 — Great!

*2014-07-18, version 1.0*

A simple and to the point app that can be used chair side with out any added time.

### 5/5 — Love this!

*2014-04-30, version 1.0*

This app is easy to use and makes a complex concept simple. The explanations are great. It is also possible to take a screen shot of the result and then upload & attach it to the patients EHR or send it directly to a patient for their education.

### 5/5 — Simple and functional - excellent

*2014-04-30, version 1.0*

It's exactly what a clinical and educational tool should be: easy to use. More than worth the price.

## Frequently asked questions about Parks Three Step

### What is the Park's Three Step app used for?

The Park's Three Step app is designed to help identify the paretic muscle in cases of acquired vertical diplopia. It uses the Park's Three-Step Test to analyze user input and suggest which extraocular muscle (EOM) is underacting.

### How does the Park's Three Step app help users understand the tests?

Beyond providing a clinical suggestion, the app explains how each of the three tests is used to determine the final result. This educational component helps users understand the primary EOMs involved in different fields of gaze.

### Is the Park's Three Step app suitable for all devices?

Yes, the Park's Three Step app is available for iPhone, iPad, and iPod devices. It is designed to be accessible on Apple's mobile operating systems.

### What is the age rating for the Park's Three Step app?

The Park's Three Step app has an age rating of 4+. This indicates it is suitable for users of all ages, though its clinical utility is primarily for medical professionals.

### How often is the Park's Three Step app updated?

The Park's Three Step app was last updated on April 8, 2017, with version 1.01. While it has not received recent updates, its core functionality remains relevant for its intended purpose.

### Does the Park's Three Step app require an internet connection to function?

The provided data does not specify offline capabilities. However, medical diagnostic tools often function offline, and the app's primary function of inputting observations and receiving suggestions suggests it may operate without a constant internet connection.

### What do users think of the Park's Three Step app?

The Park's Three Step app has received excellent user feedback, boasting a perfect 5.0-star rating from 8 reviews. This indicates a high level of user satisfaction with its functionality and educational value.

### Can I rely solely on the Park's Three Step app for clinical decisions?

The developer explicitly states that users should never fully trust an app to make clinical decisions. The app is intended as a helpful tool and educational resource, not a replacement for professional medical judgment.

## Version history (last 1 release)

### 1.01 — 2017-04-08

This app has been updated by Apple to display the Apple Watch app icon.

Just a couple small changes to make sure this app remains compatible with new versions of iOS.

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## More apps by Todd Zarwell

- [EyeDock](https://appshunter.io/ios/app/eyedock/id354889491)

All apps by Todd Zarwell: https://appshunter.io/developer/354889494

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-10.*