Reason #3: Inadequate Treatment
In the previous two installments of this series we discussed two major reasons patients still go blind from glaucoma:
- Failure to diagnose the disease
- Poor patient compliance with therapy
The third reason is less frequently discussed, but equally important:
The disease is simply not treated aggressively enough.
There are several reasons this occurs in everyday clinical practice.
The Severity of Damage Is Underestimated
One of the most common problems in glaucoma care is underestimating how advanced the disease actually is.
Clinicians often rely heavily on visual field results to judge disease severity. However, numerous studies have demonstrated that structural damage to the optic nerve often precedes measurable functional loss on standard automated perimetry. In other words, by the time a visual field defect becomes detectable, substantial retinal ganglion cell loss has already occurred.
For this reason, once a visual field defect is present, the disease should generally not be considered early glaucoma.
Another contributor to underestimation of disease severity is the reliance on global visual field indices such as mean deviation (MD), visual field index (VFI), or automated analyses including the Glaucoma Hemifield Test (GHT) and Guided Progression Analysis (GPA). While these tools are useful, they should not replace careful clinical interpretation of the complete structural and functional picture.
Population data illustrate the consequences of delayed recognition. In one analysis, more than 90% of patients predicted to progress to legal blindness already had a mean deviation worse than –6 dB in at least one eye at the time of presentation, indicating that significant disease was already present when treatment began.
These findings were highlighted in a review by Susanna and colleagues, who examined the clinical factors that continue to lead to preventable blindness in glaucoma despite modern diagnostic and therapeutic advances.6
Insufficient Reduction of Intraocular Pressure
Lowering intraocular pressure (IOP) remains the only proven modifiable risk factor for slowing glaucoma progression. However, many patients do not achieve sufficient pressure reduction.
Clinical trials demonstrate that modest IOP reductions may not be adequate to prevent progression.
In the Early Manifest Glaucoma Trial (EMGT), an average reduction of approximately 25% in IOP still resulted in progression in 59% of patients over four years.1
In contrast, studies achieving larger pressure reductions have shown better outcomes. The Collaborative Initial Glaucoma Treatment Study (CIGTS) reported IOP reductions of 35–48%, which were associated with minimal visual field progression.2 Similarly, the Advanced Glaucoma Intervention Study (AGIS) demonstrated that maintaining a mean IOP around 12 mmHg with pressures consistently below 18 mmHg significantly reduced the risk of disease progression.3
Even in normal-tension glaucoma, lowering IOP is beneficial. The Collaborative Normal-Tension Glaucoma Study showed that a 30% reduction in IOP decreased progression rates from 60% to 20%.4
These observations reinforce the point emphasized by Susanna et al. that inadequate pressure reduction remains one of the major contributors to preventable glaucoma blindness in real-world practice.6
IOP Is a Dynamic Parameter
Another important factor is that IOP fluctuates throughout the day and night.
Many clinicians base treatment decisions on single measurements obtained during office visits. However, research has shown that more than half of IOP peaks occur outside office hours, meaning they are frequently missed during routine clinical examinations.
Studies using diurnal pressure curves have demonstrated that peak pressures detected during extended monitoring are often higher than those observed during routine office measurements.5 These transient IOP spikes may play an important role in glaucoma progression.
Consequently, relying solely on office measurements can lead clinicians to overestimate the degree of pressure control.
Failure to Evaluate the Rate of Progression
One of the most important determinants of visual disability in glaucoma is the rate at which the disease progresses.
Two patients may have similar visual field defects at a given point in time, yet their long-term outcomes may be very different. One patient may progress slowly and never develop significant disability, while another may lose vision rapidly.
Despite its importance, studies show that clinicians often do not formally assess progression rates, frequently due to time constraints, insufficient data, or unfamiliarity with progression analysis tools. As a result, testing intervals and monitoring strategies often differ substantially from guideline recommendations.
Susanna and colleagues have emphasized that decisions regarding treatment intensity should incorporate real-world estimates of progression risk, rather than relying solely on randomized clinical trial populations.6
Conclusion
Preventing blindness from glaucoma requires more than simply diagnosing the disease and prescribing medication.
Clinicians must also:
- Recognize the true severity of structural damage
- Achieve adequate intraocular pressure reduction
- Understand that IOP fluctuates throughout the day
- Carefully monitor the rate of disease progression
When these factors are not addressed, glaucoma may continue to progress despite treatment.
And when progression goes unrecognized, preventable vision loss can occur.
References
- Heijl A, Leske MC, Bengtsson B, et al. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol.2002;120:1268-1279.
- Musch DC, Gillespie BW, Lichter PR, et al. Visual field progression in the Collaborative Initial Glaucoma Treatment Study. 2009;116:200-207.
- The AGIS Investigators. The Advanced Glaucoma Intervention Study: the relationship between control of intraocular pressure and visual field deterioration. Am J Ophthalmol.2000;130:429-440.
- Collaborative Normal-Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the treatment of normal-tension glaucoma. Am J Ophthalmol.1998;126:498-505.
- Barkana Y, Anis S, Liebmann J, et al. Clinical utility of intraocular pressure monitoring outside of normal office hours in patients with glaucoma. Arch Ophthalmol.2006;124:793-797.
- Susanna R Jr, Vessani RM. Why do people still go blind from glaucoma?Translational Vision Science & Technology. 2014;3(2):1. https://doi.org/10.1167/tvst.3.2.1
Final Thoughts
In this series we examined three major reasons why patients still lose vision from glaucoma despite the availability of effective diagnostic tools and treatments.
The first is failure to diagnose the disease early enough. Many patients with glaucoma remain undiagnosed for years because early structural damage is subtle and often missed during routine examinations.
The second is poor compliance with therapy. Even when treatment is prescribed, a significant proportion of patients discontinue their medications within months—often without informing their physician. Poor adherence remains one of the most persistent challenges in glaucoma care.
The third is inadequate treatment once the disease has been diagnosed. This may occur when the severity of damage is underestimated, when intraocular pressure is not reduced sufficiently, or when progression is not monitored carefully.
Taken together, these three factors explain why preventable vision loss from glaucoma still occurs. Importantly, each of them is potentially correctable.
Improved diagnostic strategies, better patient education, and more systematic approaches to treatment and monitoring can significantly reduce the risk of blindness.
Glaucoma does not inevitably lead to vision loss.
Preventing blindness requires early diagnosis, consistent treatment, and thoughtful long-term management.
Blindness from glaucoma is often described as inevitable. In reality, most cases of severe vision loss occur not because the disease is untreatable, but because it is not diagnosed early enough, not treated aggressively enough, or not followed carefully enough.
When glaucoma is identified early and managed appropriately, the vast majority of patients can retain useful vision for the rest of their lives.
Reducing blindness from glaucoma will not come from new medications alone. It will come from improving how we diagnose, treat, and monitor the disease in everyday clinical practice.
That goal—eliminating preventable blindness from glaucoma—should remain the central mission of everyone involved in glaucoma care.