Ellipsoid zone width change

About this calculator

Enter the ellipsoid zone width from two OCT scans to see the change in micrometres, as a percentage and per year.

What you need

• The date and EZ width (µm) from each scan, measured in the same direction
• Both scans from the same device with the same alignment

How it is calculated

Change = later − earlier width. Percentage change = 100 × change ÷ earlier width. Yearly change = change ÷ (days ÷ 365.25). Horizontal and vertical widths are kept separate.

What the result can and cannot tell you

Ellipsoid zone width has been studied mainly in retinitis pigmentosa. Scan alignment, grading and disease stage all affect it. Width is a structural measure, not the same as area or how well you see, so it is read alongside visual acuity and visual fields.

References

1. A comparison of progressive loss of the ellipsoid zone band in autosomal dominant and X-linked retinitis pigmentosa
2. Netra Eye Institute: Retinitis pigmentosa

Related

• OCT macular thickness change
• Amsler grid self-check
• Geographic atrophy growth
• Retinitis pigmentosa 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.