Serial imaging only means something if the comparison is fair, and the commonest way it stops being fair is invisible: the patient was scanned on a different device, or the same device after a software update, or by a technician using a different scan protocol.
So fix what you can. Record the device and software version in the note alongside the measurement. Use the same scan pattern each time and the follow-up or registration mode where the machine offers one, so the scan lands in the same place. Have the technician check axial length or refraction where the measurement is magnification-sensitive. And where a patient arrives with imaging from elsewhere, treat the outside measurement as a separate series rather than as the first point in yours - a change between two different machines is a change in machines until proven otherwise.
When a number moves and the clinical picture has not, check the acquisition before you act on it. Re-scan on the original device if you can. Most of the surprising changes in serial retinal and choroidal measurements resolve at that step.
- Record device and software version with every measurement you intend to compare over time
- Use follow-up or registration mode so serial scans sample the same retina
- Treat imaging from another centre as a separate series, not a baseline for yours
- Re-scan before acting on an unexpected change in a serial measurement
- Correct for ocular magnification where it applies, particularly in high myopia
Why it matters
A measurement that looks like progression is often a change of equipment, and nothing in the chart says so.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for ophthalmology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free