That is why usability engineering is a regulatory and safety discipline, not just a design activity. For medical device manufacturers, IEC 62366-1 provides a structured way to identify, reduce, and evaluate risks connected to the user interface.
What IEC 62366-1 Covers
IEC 62366-1 focuses on applying usability engineering to medical devices where use-related problems could affect safety. The standard describes a process for analysing users, intended use, use environments, user interface characteristics, and potential use errors.
The user interface is broader than the screen or physical controls. It can include:
- Hardware controls and displays
- Software screens and workflows
- Alarms, indicators, and feedback
- Packaging and setup materials
- Labelling and instructions for use
- Training materials and other safety-related information
The goal is not simply to make the product pleasant to use. The goal is to reduce the likelihood of use errors that could lead to harm.
Usability vs User Experience
Usability and user experience are related, but they are not the same.
Usability asks whether intended users can use the device safely and effectively in the intended environment. User experience is broader and may include satisfaction, brand perception, convenience, and emotional response.
For medical devices, regulators are primarily concerned with safety and effectiveness. A device can look modern and feel polished while still having serious usability risks. Conversely, a simple interface may be acceptable if users can complete critical tasks correctly and safely.
Why Use Errors Matter
A use error is a problem that occurs when a user action, or lack of action, leads to a different result than intended. Use errors are usually not best handled by blaming the user. They often point to problems in the design of the device, interface, labelling, workflow, or training.
Common causes include:
- Similar-looking controls
- Ambiguous icons or abbreviations
- Poor alarm prioritisation
- Missing feedback after a user action
- Instructions that do not match real-world use
- Workflows that rely too heavily on memory
- Designs that do not account for stress, fatigue, gloves, lighting, noise, or limited training
A strong usability engineering process looks at these risks early, tests assumptions with real users, and confirms that risk controls actually work.
Key Activities in the Usability Engineering Process
1. Define intended users and use environments
Start by identifying who will use the device. This may include healthcare professionals, patients, caregivers, service technicians, or other groups. Each group may have different skills, expectations, limitations, and responsibilities.
The use environment also matters. A hospital, ambulance, home, laboratory, and operating room create very different usability challenges.
2. Identify critical tasks
Critical tasks are user actions where incorrect or missed performance could cause harm. These tasks deserve special attention because they directly influence the usability evaluation strategy.
Examples might include setting a dose, connecting tubing, interpreting an alarm, preparing a sample, confirming patient data, or responding to device failure.
3. Analyse use-related risks
Usability engineering should connect with the broader risk management process. Manufacturers should identify foreseeable use errors, hazardous situations, possible harms, and risk control measures.
Good analysis considers how users perceive information, understand it, decide what to do, and act. This helps teams find design weaknesses before they become validation failures.
4. Design the user interface and risk controls
Risk controls should be built into the product wherever possible. Labelling and training may help, but they are usually weaker controls than a clear, intuitive, well-constrained design.
Useful controls may include clearer status feedback, forcing functions, confirmation steps for high-risk actions, better alarm design, improved physical differentiation, simplified workflows, and more accessible instructions.
5. Conduct formative evaluation
Formative evaluation happens during development. It helps the team learn where users struggle and improve the design before final validation.
Methods may include expert reviews, cognitive walkthroughs, simulated-use sessions, prototype tests, interviews, and observation. The purpose is to find problems early, not to prove final compliance.
6. Conduct summative evaluation
Summative evaluation is typically performed when the design is mature. It provides evidence that intended users can perform critical tasks safely and effectively under realistic conditions.
A summative usability test should use representative users, realistic scenarios, appropriate environments, and predefined acceptance criteria. Any observed use problems should be analysed carefully, especially when they involve critical tasks.
Documentation Manufacturers Should Maintain
A usability engineering file should tell a coherent story from risk identification to final evaluation. It should make clear what was analysed, what was tested, what changed, and why the remaining risk is acceptable.
Typical documentation includes:
- User profiles
- Use environments
- User interface specification
- Use-related risk analysis
- Critical task analysis
- Formative evaluation plans and results
- Summative evaluation protocol and report
- Residual risk evaluation
- Links to labelling, training, and risk management documentation
The file should be practical and traceable. Auditors and reviewers should be able to understand how usability risks were identified, reduced, and evaluated.
EU and FDA Considerations
In the EU, usability connects to the Medical Device Regulation's general safety and performance expectations, including safe use, suitable information for users, and risk reduction.
In the United States, FDA guidance on human factors and usability engineering explains how manufacturers should consider users, use environments, and user interfaces during device development. FDA also expects human factors information in certain marketing submissions based on risk.
Manufacturers planning to market in both the EU and the U.S. should align their usability engineering strategy early. Doing so can reduce duplicated work and help create a stronger technical file or submission package.
Common Mistakes to Avoid
Many usability problems come from treating the process as a late-stage documentation exercise. By the time a final usability test fails, design changes are usually more expensive and timelines are harder to protect.
Avoid these mistakes:
- Starting usability work after the design is already frozen
- Testing only employees or highly trained internal users
- Treating user preference surveys as proof of safe use
- Ignoring packaging, labelling, setup, cleaning, or maintenance tasks
- Assuming training can compensate for a confusing interface
- Failing to connect usability findings to risk management
- Under-documenting design changes made after formative studies
Practical Takeaway
Usability engineering is most effective when it starts early and stays connected to design, risk management, clinical workflow, and regulatory strategy. IEC 62366-1 gives manufacturers a process for doing this in a structured way.
A well-run usability process does more than support compliance. It helps create medical devices that users can understand, trust, and operate safely when it matters most.