Nerve fiber layer trend

About this calculator

Enter serial OCT thickness values for one measurement to see the trend over time, or the change from first to last scan when there are fewer than five scans over two years.

What you need

• The date and thickness of each scan for one measurement (RNFL average, one RNFL sector, GCIPL or GCC)
• Scans from the same device, software version and scan protocol

How it is calculated

Each test date is converted to years from the first test. The trend is an ordinary least-squares line of the result against time. Its 95% confidence interval uses the standard error of the slope (residual variance with n − 2 degrees of freedom) and the two-sided Student t value. The trend is shown only with at least 5 included tests spanning at least 2 years; shorter series show the change from the first to the last test.

What the result can and cannot tell you

Keep RNFL, GCIPL and GCC as separate series, and global and sector values separate. These layers thin slowly with age, scan quality and segmentation can shift values, and very thin layers reach a floor where further loss is hard to measure. Your eye doctor interprets the trend with your visual fields and any treatment changes.

References

1. Clinical factors associated with long-term OCT variability in glaucoma
2. Optical coherence tomography in glaucoma: a practical guide
3. Netra Eye Institute: Glaucoma

Related

• Eye pressure reduction
• Ocular perfusion pressure
• Eye pressure fluctuation
• Glaucoma guide
• All eye calculators

For information only. These tools explain numbers and do not replace an eye examination or your eye doctor’s advice. Values you enter stay in your browser.