Why Your Glaucoma Scan Numbers Depend on the Software: An OCT Angiography Study of 93 Patients

Glaucoma care relies on measurements over time: eye pressure, visual fields, and scans of the optic nerve and retina. A newer scan, OCT angiography (OCTA), maps the tiny blood vessels of the retina without dye. A study published in Optometry and Vision Science shows why the numbers from these scans must be interpreted carefully.

What the researchers did

A team working with data from a glaucoma study at the Lions Eye Institute in Australia took OCTA images of the macula from 93 people with glaucoma (average age 67), scanned at two visits about 113 days apart. They then ran the same images through two free, open-access analysis programs, called EA-tool and OCTAVA, which use different methods to decide which pixels count as blood flow.

What they found

• Both programs were similarly repeatable from visit to visit.
• But they gave different answers from the same images. OCTAVA reported vessel density about 8.4 percentage points higher on average and a larger central vessel-free zone.
• With both programs, higher vessel density was linked to better central visual field sensitivity.
• Based on measurement noise, a change in average vessel density of more than about 5% (EA-tool) or 6% (OCTAVA) between visits is unlikely to be noise alone.
• One measure, the roundness of the central vessel-free zone, was not reliable with either program.

The authors concluded that the tools cannot be used interchangeably to monitor glaucoma and that absolute values should not be compared across platforms.

Why this matters to you

The same lesson applies to most glaucoma tests. A number from one machine or software version may not match a number from another. What matters most is the trend on the same device, interpreted by the same practice over time.

• If you change eye doctors, bring or request your prior scans and visual fields so a new baseline is not started from zero.
• Ask whether your follow-up scans are done on the same machine.
• OCTA is still mainly a research and supporting tool in glaucoma; standard OCT of the nerve fiber layer and visual fields remain the core tests.

For more reading on eye health, see laservisioncost.com.

Source: Study: OCTA analysis tools report different macular vessel density values for glaucoma (Optometry Times, 10/23/2026). This article is an educational summary written by Khanna Vision Institute and is not a substitute for medical advice.