Inside Eye Consults · Glaucoma
Assessing optic-disc progression
I use a consistent sequence when reading a ZEISS CIRRUS RNFL report. I check the patient and scan quality first, inspect the segmentation, then assess the thickness maps and thickness profile. Progression software comes after those checks.
The standard report
My reading sequence
When a serial OCT appears to show progression, the first question is whether the change is real. I do not begin with the quadrant summaries or normative colour labels.
I work through the report in the same order each time. This makes it less likely that an artefact or an unusually shaped disc will be mistaken for progression.
Confirm the patient and scan quality
First, I check the patient's name and identifier. I then check the signal strength. Poor signal strength can produce false blue bands on the RNFL thickness map, so a low-quality scan should not be used to call progression.
Inspect the segmentation scans
At the bottom of the report, I inspect the extracted horizontal, extracted vertical and RNFL circular tomograms for both eyes. The circular tomogram is the direct check of RNFL layer segmentation.
Segmentation errors, movement and decentration usually produce black or missing areas rather than a false blue band. These errors still need to be recognised before the thickness maps are interpreted.
- Extracted horizontal tomogram
- Extracted vertical tomogram
- RNFL circular tomogram
Read the RNFL thickness maps
These are the two maps I use most. In a healthy eye, the superior and inferior nerve-fibre bundles form distinct red and yellow bands.
Progression may appear as a blue band developing within one of these bundles and then widening over time. I would want a new blue band to persist on a repeat scan before calling it progression.
Read the thickness profile
I look at the height and width of the superior and inferior peaks. Over time, a change in the shape of the curve—or a broader loss of its apparent volume—can be more informative than one summary number.
The green normative range can create false concerns in myopic tilted discs. I therefore interpret the curve's shape and serial change rather than treating the normative band as a diagnosis.
Serial analysis
GPA and FORUM Glaucoma Workplace
When serial scans were acquired on the same machine, the built-in Guided Progression Analysis can match, rotate and recentre them and generate a progression report. Where the scans are available in ZEISS FORUM, FORUM Glaucoma Workplace provides a more comprehensive longitudinal workspace.