Why People (Still) Go Blind from Glaucoma

Reason #1: Underdiagnosis

It is universally recognized — and has been for more than four decades — that the number one reason people still lose vision from glaucoma is that the disease remains undiagnosed. Both landmark papers on this topic (“Why Do Some People Go Blind from Glaucoma?” in 1982 and “Why Do People Still Go Blind from Glaucoma?” in 2015) identify underdiagnosis as the leading cause.¹⁻²

However, a closer look reveals a much more complex landscape. Patients remain undetected for multiple overlapping reasons — some tied to access and affordability, others to clinical decision-making and evolving diagnostic technology.

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Barriers to Detection: Beyond “Patients Don’t Get Eye Exams”

1. Limited Access and Affordability

Many people simply cannot afford routine eye care. They may lack vision insurance, have limited coverage, or be unable to meet out-of-pocket costs. Even those with insurance may not prioritize an eye examination if they feel they have “no problems.”

1. Absence of Symptoms

Glaucoma is asymptomatic until late in the disease.
Emmetropes and patients with mild refractive error — who often skip routine care for decades — frequently present only once presbyopia begins in their 40s or 50s. By then, early glaucomatous damage may already be present.

This is so common that emmetropia itself has been discussed as a potential risk factor, not because it biologically predisposes patients to the disease, but because it delays examination.³

1. Geographic Barriers

Large segments of the population live in underserved regions with inadequate access to optometrists or ophthalmologists. This structural issue remains a major contributor worldwide.⁴

Although access and affordability are major factors, they lie largely outside the direct control of clinicians. Where eye care providers can make the greatest impact is within the examination itself — and here, the evidence shows we continue to fall short.

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The Diagnostic Problem: We Miss Too Many Cases — and Mislabel Others

The Thessaloniki Eye Study revealed two striking findings:

• About 50% of undiagnosed glaucoma cases were missed during routine care.⁵

• Even more concerning, **60% of individuals labeled as having glaucoma actually did not have the disease.**⁵

In practical terms:
Sensitivity ~50% and specificity ~40%.

These numbers reflect a time when diagnostic tools were limited — but even today, despite enormous technological advances, the pattern persists.

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A Look Back: Why Diagnosis Was So Difficult

When I began practice in 1983, diagnostic tools were rudimentary:

Optic Nerve Examination

For decades, the direct ophthalmoscope (invented by Helmholtz in 1851) was the standard. Its key limitations:

• non-magnified

• monocular

• non-stereoscopic

• narrow field

Fundus lenses introduced in the early 1990s finally allowed stereoscopic viewing. Many nerves once described as “cup 0.2” suddenly became “0.9.”

Visual Field Testing

Before automated perimetry, most practices relied on tangent screens.
Goldmann perimetry was excellent but limited to academic centers.

This changed in 1986 with the arrival of automated static perimetry, and eventually with the development of robust progression analysis algorithms — essential for monitoring change over time.

The Pressure Dogma

Prior to the Ocular Hypertension Treatment Study (OHTS) in 2002, the prevailing belief was simple:

• IOP > 21 mmHg → glaucoma

• IOP ≤ 21 mmHg → no glaucoma

This misconception alone explains a large portion of over- and under-diagnosis.⁶

Given these historical constraints, poor diagnostic yield was almost inevitable.

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Where We Stand Now: A Different Disease with Better Tools

Today, it is firmly established that glaucoma is a disease of the optic nerve, not of pressure alone.⁷

• People with normal pressures can have glaucoma (“normal-tension glaucoma”).

• Many with pressures above 21 mmHg will never develop damage (ocular hypertension).⁶

The most transformative innovation has been Spectral-Domain Optical Coherence Tomography (SD-OCT):

• real-time, high-resolution 3D imaging

• quantitative RNFL and GCIPL measurements

• highly sensitive progression analysis

Its ability to track structural change over time fundamentally reshaped glaucoma care.

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So Why Do We Still Underdiagnose Glaucoma?

In my view, the primary reason is improper interpretation and underutilization of OCT data.

Common factors include:

• Over-reliance on pie charts, global metrics, and color codes

• Failure to examine the actual B-scan images

• Limited exposure to OCT during training (especially for mid-career clinicians)

• Loss of detailed optic nerve examination skills as reliance shifts toward device-generated summaries

• Variability in training, adoption, and clinical workflow integration

These issues reflect an educational gap, not a technological one.

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The Path Forward: Education

Of all the reasons people still go blind, this is the one where we can make the greatest immediate impact.

And that is precisely the mission of Evergreen Eye Consultants:
reducing blindness from glaucoma through comprehensive, evidence-based education — for clinicians and patients alike.

Our work includes:

• national and regional lectures

• OCT interpretation workshops

• clinical decision-making training

• practical guidance on diagnosing and managing glaucoma

Our aim is simple:
Improve diagnostic accuracy, elevate standards of care, and help clinicians teach their colleagues.

But underdiagnosis is only the first part of the story — and the first major reason people still lose vision to this disease.

Stay tuned for the next installment.

— J.J. O’Donnell, OD, FAAO (Dipl. Glaucoma)
Evergreen Eye Consultants

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Selected Citations

1. Kolker AE. Why do some people go blind from glaucoma? Ophthalmology. 1982;89(9):991–998.

2. Weinreb RN, Aung T, Medeiros FA. Why do people (still) go blind from glaucoma? Trans Am Ophthalmol Soc. 2015;113:T8.

3. Tham YC et al. Global prevalence of glaucoma… Ophthalmology. 2014;121(11):2081–2090.

4. Stein JD et al. Geographic and socioeconomic barriers to glaucoma care. Ophthalmology. 2011;118(8):1549–1556.

5. Topouzis F et al. Prevalence of glaucoma in the Thessaloniki Eye Study. Am J Ophthalmol. 2007;144(4):511–519.

6. Kass MA et al. The Ocular Hypertension Treatment Study. Arch Ophthalmol. 2002;120(6):701–713.

7. Weinreb RN, Khaw PT. Primary open-angle glaucoma. Lancet. 2004;363(9422):1711–1720.