Privacy

Patient Data Privacy: Why 100% Local Measurement Changes Everything

September 4, 2026 · 3 min read

A centering measurement almost always relies on a photo of the client's face. That is sensitive personal data, and the question of where it goes, where it is stored, and who can access it deserves to be asked just as seriously as it would be for a medical record.

The most common setup

Many modern measurement tools send the photo or the extracted data to a server — the equipment manufacturer's, sometimes a partner lens group's — for processing or storage. That is a perfectly legitimate architectural choice in many cases, but it means a longer GDPR chain of responsibility: the store, the equipment manufacturer, the hosting provider, and potentially other subcontractors.

The alternative: processing everything in the browser

A measurement can also be computed entirely in the browser of the device taking the photo, with nothing sent to a server at all. The photo, the detected landmarks, the final calculation: everything stays local, and nothing leaves the device.

At IO Tech This is the principle we built the tool on from day one: no photo, no measurement, no client data is ever sent to a server. All of the computation — landmark detection, pupillary distance, centering height — runs in the browser of the phone used in-store. For the optician, that means a much shorter GDPR chain of responsibility: the data never leaves their own device.

It isn't just a technical argument — for many clients, it's also a trust argument that gets noticed, and talked about.

A measurement that never leaves your device

No client data is ever sent to a server, at any point.

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