Project Insights
Designing for usability: Improving the design of a medical device before user testing
19 Feb 2025
Research | Usability | UI Design | MedTech
User testing is essential for refining medical device interfaces, but it can be costly and time-consuming. Optimising the system with usability specialists is a cost-effective way to identify and resolve design flaws early, and ensures that user testing focuses on validation rather than discovery.
A software agency approached me with a prototype of a new point-of-care diagnostic device they were developing for a client. They had scheduled three days of user testing for the following week, and wanted to improve the usability of the current design. My challenge was to identify and address usability issues in the existing prototype and design a more intuitive, user-friendly version before it was tested with real users.
The research: Identifying usability barriers through interface analysis
To assess the usability of the current system, I used two expert evaluation techniques:
Cognitive Walkthrough: I stepped into the user’s shoes and carried out two key user tasks in the system – perform a test, and view test results – to pinpoint pain points in the task flows.
Heuristic Evaluation: I conducted a systematic review of the system based on Nielsen’s 10 usability heuristics to identify key areas of concern.
The findings: Navigation issues, ambiguous labels, and lack of guidance
The existing prototype had several strengths: it delivered essential functionality, effectively communicated test progress, and featured a visually appealing, minimalist design that promoted focus by eliminating unnecessary clutter.
The evaluations, however, revealed several usability challenges that hindered efficiency, clarity, and user confidence. Inconsistent navigation and signposting, ambiguous labels and action clarity, and a lack of visual instructions made it harder for users to complete tasks. Below are some of the key usability issues identified.
Missing status bar: The interface lacked a status bar to provide users with essential real-time feedback, such as device connectivity, Wi-Fi status, and result upload readiness. Additionally, the absence of date and time visibility reduced efficiency in a medical work setting where precise timing is critical.
Unclear navigation labels: The global navigation relied on unlabelled icons, some of which were non-standard, making it difficult for users to navigate and complete tasks, such as locating test results. Without universally recognised iconography, text labels are essential to ensure clarity and prevent cognitive strain.
Missing log-out button: The interface lacked a visible log-out button, which is essential in medical settings where multiple users may share the same device. Without a clear way to securely log out, there is a risk of unauthorised access to sensitive information. Implementing a prominent log-out option would enhance security and ensure compliance with standard medical protocols.
Missing clear entry points: The home screen lacks clear entry point for key tasks, including performing a test and viewing test results, creating unnecessary friction in the core workflow.
Missing screen title: The interface lacked clear screen titles in conventional places, making it difficult for users to orient themselves within the system and understand the current context. Clear signposts are essential for wayfinding and reducing cognitive load, especially in high-stakes medical environments.
Missing guidance: The test workflow lacked clear visual guidance for key actions, such as opening and closing the device drawer or scanning the sample code. Without intuitive instructions, users may experience uncertainty, leading to errors or delays in the testing process. Incorporating visual cues or step-by-step prompts would improve usability and reduce the risk of user mistakes.
Missing option to cancel test: The test workflow lacked a clear option to cancel or abort the process, limiting user control and flexibility. In medical environments, the ability to stop a test when needed is critical for safety and efficiency. Introducing a cancel button would enhance usability by allowing users to recover from errors or unexpected situations without completing an unwanted test.
Unconventional placement of back-button: The placement of the back button was inconsistent across screens – sometimes positioned on the top right, other times on the top left – causing confusion and disrupting navigation. Additionally, some screens lacked a back button entirely, limiting users' ability to return to the previous step. Consistent placement and availability of the back button are essential for effective navigation.
Unclear screen titles: Most screens lacked a screen title, and those that had one, was unclear – such as the test results screen, labelled as 'Data List'. This ambiguity can cause confusion and make it harder for users to quickly identify critical information. Using a more task-specific title, such as 'Test Results,' would improve clarity and usability.
Ambiguous button labels: Some of the screens contained buttons with ambiguous labels, making it difficult to understand their purpose. Clear, action-oriented labelling is essential to ensure users can confidently navigate the interface and make informed decisions.
Unclear error recovery: Error messages lacked clear guidance on how users could recover from issues, leading to potential frustration and uncertainty.
Misaligned visual hierarchy: The visual hierarchy did not prioritise critical information relevant to users, making it harder for them to quickly identify the necessary steps to resolve errors. Ensuring actionable error messages and a user-centred hierarchy would improve clarity and make it easier to resolve the issue.
Dark mode design: Finally the system was designed in dark mode, which is not optimal for medical environments where bright lighting is the norm. This contrast mismatch can reduce readability and strain visibility, potentially impacting efficiency and accuracy. A light mode or adaptable theme would better align with the typical medical setting.
The redesign: Improved navigation, clarity, and user guidance
With these usability challenges identified, I set out to design a new prototype that would deliver a more intuitive user experience and better support the workflows of medical professionals. Since the focus was on usability rather than visual aesthetics at this stage, I created a medium-fidelity prototype to refine the interaction design and task flows.
Hub-and-spoke navigation model: I designed a new navigation system, using the home screen as the central access point, making it easier to navigate and access key functions.
Device status bar: The new design uses a status bar displaying critical system information, such as device connectivity, Wi-Fi status.
Clear entry points to essential tasks: With the new buttons on the home screen, users can quickly and easily initiate a test, review result history, and access settings, reducing friction in task completion.
Logged-in user visibility: The new interface clearly displays the currently logged-in user, improving accountability and security in shared-use environments.
Prominent log-out button: A clearly visible log-out option ensures secure session management and prevents unauthorised access.
Real-time status updates of testing modules: The homepage provides immediate feedback on the test module’s operational state, enhancing efficiency and reducing uncertainty.
Clear error resolution guidance: The redesigned test error screens provide users with instructions in plain language, on how to resolve issues. Instead of using technical jargon, the screen outlines specific, step-by-step solutions, helping users quickly address the problem.
Improved visual hierarchy: Critical information is prioritised based on user needs, ensuring that the most important details – such as the error description and resolution steps – are immediately visible and easy to follow.
Improved screen orientation: The new navigation system uses a top bar with a clear screen title, which ensures users immediately understand where they are within the system and improves wayfinding.
Consistent navigation: Conventionally placed back buttons allows users to easily return to the previous screen without frustration.
Clear and intuitive action buttons: Buttons now feature explicit, action-oriented labels, eliminating ambiguity and making it easier for users to confidently complete key tasks.
Clear visual guidance: The new screen flow for performing a test includes clearer steps and visual instructions to help users navigate the test process with confidence.
Prominent cancel button: Users now have greater control with a visible option to cancel or abort a test, improving flexibility.
Confirmation step before test initiation: A final confirmation message displays the test type and sample ID, prompting users to review and verify details before the test begins, reducing the risk of errors.
Clear action buttons after test initiation: Once the test starts, clear-labelled action buttons encourage users to proceed in their workflow.
Light mode alternative: Finally, I redesigned the interface in light mode, which better aligned with typical lighting conditions in medical environments, for improved readability and visibility.
The impact: A cost-effective, user-friendly design ready for testing
Although I was not part of the user testing phase, my work laid a strong foundation for a more effective validation process. My contributions resulted in:
✔ Reduced friction before usability testing, allowing the agency to focus on refining the design rather than discovering and fixing core usability issues.
✔ Saved time and costs by addressing major usability flaws before they escalated into larger problems.
✔ A clear, test-ready design that served as a blueprint for user validation and future iterations.
Why UX matters in medical device design
While user feedback is essential for medical device compliance, it’s not the only way to uncover usability issues. This project demonstrates how expert-driven UX evaluation can proactively identify and resolve friction points, preventing costly issues down the line.