Concepts

Normal-tension glaucoma

In normal-tension glaucoma (NTG) the optic nerve is damaged although IOP never measures above 21 mmHg. It isn't rare: in Japan's Tajimi Study, 92% of people with open-angle glaucoma had IOP of 21 mmHg or less.[5]

Lowering IOP still helps many NTG patients. In the Collaborative Normal-Tension Glaucoma Study, a 30% reduction slowed visual-field loss once the effect of cataract was accounted for.[6] But some patients get worse at low pressure, which points to other drivers, above all the blood supply of the optic nerve.[7]

Eye pressure (IOP)within 10–21 mmHgBlood supplylow or unstable perfusionmechanical strain at the lamina cribrosatoo little or unstable blood flowoptic nerveheadGanglion-cell axons diethe cup widens, the rim thinsblind spots in the visual field

IOP is normal, yet the nerve is damaged. Many researchers think too little or unstable blood supply weighs more here, which is what GlaucomAI's vascular axis looks for.

Interactive SchematicConceptual: pressure and blood supply both act on the optic nerve head, with different weight in different patients.
Key facts
  • Tajimi: open-angle glaucoma in 3.9% of people aged 40 and over, and 92% of them with normal IOP.[5]
  • Vascular factors discussed in NTG include low or unstable blood pressure, night-time dips and a tendency to vasospasm.[7, 8]
In GlaucomAI

A screening model trained on PAPILA with age, sex and IOP misses 33 of the 63 LSMU NTG patients. That blind spot is why GlaucomAI looks beyond pressure.

References on this page

  1. 5.Iwase A, Suzuki Y, Araie M, et al. The prevalence of primary open-angle glaucoma in Japanese: the Tajimi Study. Ophthalmology. 2004;111(9):1641–1648. PubMed search ↗
  2. 6.Collaborative Normal-Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the treatment of normal-tension glaucoma. Am J Ophthalmol. 1998;126(4):498–505. PubMed ↗
  3. 7.Flammer J, Orgül S, Costa VP, et al. The impact of ocular blood flow in glaucoma. Prog Retin Eye Res. 2002;21(4):359–393. PubMed search ↗
  4. 8.Flammer J, Konieczka K, Flammer AJ. The primary vascular dysregulation syndrome: implications for eye diseases. EPMA J. 2013;4(1):14. PubMed search ↗
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