Deep dive into Ocular hypertension ( OHT )

By Dr. Phornrak Sriphon, Ophthalmologist and Glaucoma Specialist

Introduction

"Your eye pressure is high, but you do not have glaucoma."

This is one of the most common statements ophthalmologists make during an eye examination, yet it is also one of the most misunderstood. For many patients, hearing this immediately raises concerns about future vision loss. Others assume that because they do not have glaucoma, no further follow-up is necessary. In reality, neither interpretation is entirely correct.

This condition is known as Ocular Hypertension (OHT), which refers to elevated intraocular pressure (IOP) in the absence of structural or functional evidence of glaucomatous optic nerve damage. In other words, although the intraocular pressure is higher than normal, examinations of the optic nerve head, retinal nerve fiber layer (RNFL), and visual field remain within normal limits. Therefore, these patients do not meet the diagnostic criteria for glaucoma.

This naturally leads to an important clinical question:

Should every patient with Ocular Hypertension be treated?

Historically, treatment decisions were largely based on the level of intraocular pressure alone, as elevated IOP has long been recognized as the most important modifiable risk factor for glaucoma. However, over the past two decades, evidence from high-quality clinical research—most notably the Ocular Hypertension Treatment Study (OHTS)—has fundamentally changed this approach.

The OHTS demonstrated that although lowering intraocular pressure significantly reduces the risk of developing glaucoma, the majority of patients with ocular hypertension do not progress to glaucoma during the first five years of follow-up. This finding suggests that treating every patient solely because of elevated IOP may result in unnecessary treatment for many individuals, while those at genuinely high risk may benefit from early intervention to prevent irreversible optic nerve damage.

Consequently, the management of Ocular Hypertension has shifted from focusing solely on intraocular pressure to a more comprehensive individualized risk assessment. Rather than relying on IOP alone, clinicians now consider multiple risk factors—including age, central corneal thickness (CCT), optic nerve appearance, visual field findings, and other clinical characteristics—to estimate an individual's likelihood of developing Primary Open-Angle Glaucoma (POAG).

In this review, we explore the current understanding of Ocular Hypertension, beginning with its definition and clinical characteristics, followed by the landmark studies that have shaped modern management strategies. We also discuss the role of the OHT Risk Calculator, the principles of individualized risk assessment, indications for initiating treatment, and the current evidence supporting both medical therapy and Selective Laser Trabeculoplasty (SLT).

Ultimately, the goal of managing Ocular Hypertension extends far beyond lowering a numerical eye pressure value. The primary objective is to prevent irreversible optic nerve damage, preserve visual function, and maintain patients' quality of life over the long term.

By the end of this article, readers will appreciate that Ocular Hypertension is not simply a condition of elevated eye pressure, but rather a clinical entity that requires careful risk stratification and evidence-based decision-making to ensure that each patient receives the most appropriate, individualized care.

Topic 

1. What Is Ocular Hypertension?

2. Can High Eye Pressure Turn into Glaucoma?

3. How Is Your Risk Assessed?

4. When Should Treatment Start?

5. What Is the Goal of Treatment?

6. Key Takeaways

Topic 1  What Is Ocular Hypertension?

What Is Ocular Hypertension?

Ocular Hypertension (OHT) refers to a condition in which the intraocular pressure (IOP) is higher than normal—generally greater than 21 mmHg—but there is no evidence of damage to the optic nerve and no visual field loss. Therefore, individuals with Ocular Hypertension do not meet the diagnostic criteria for glaucoma, according to the European Glaucoma Society (EGS) Guidelines, 6th Edition (2025).

One important concept to understand is that high eye pressure is not the same as glaucoma. Instead, elevated IOP is the most important known risk factor for developing glaucoma. In other words, people with Ocular Hypertension have a higher risk of developing Primary Open-Angle Glaucoma (POAG) than the general population, but not everyone with Ocular Hypertension will eventually develop glaucoma.

For this reason, diagnosing Ocular Hypertension involves much more than measuring eye pressure alone. A comprehensive eye examination is required to confirm that the optic nerve remains healthy and to rule out other conditions that may cause elevated eye pressure.

How Is Ocular Hypertension Diagnosed?

In general, the diagnosis of Ocular Hypertension includes the following features:

• Intraocular pressure (IOP) greater than 21 mmHg without the use of pressure-lowering medication.

• Normal visual field testing (Standard Automated Perimetry) with no evidence of glaucomatous visual field defects.

• A healthy optic nerve head (optic disc) and normal retinal nerve fiber layer (RNFL), with no signs of glaucomatous optic neuropathy on clinical examination or Optical Coherence Tomography (OCT).

• Open angles on gonioscopy, after excluding primary angle closure or intermittent angle closure.

• No other eye diseases or secondary causes of elevated IOP, such as uveitic glaucoma, pigment dispersion syndrome, pseudoexfoliation syndrome, or steroid-induced ocular hypertension.

How Is Ocular Hypertension Different from Glaucoma?

Although patients with Ocular Hypertension have elevated eye pressure, they do not have the structural or functional damage that defines glaucoma.

Glaucoma is diagnosed when there is evidence of optic nerve damage and/or corresponding visual field loss. In contrast, patients with Ocular Hypertension have elevated eye pressure without detectable damage to the optic nerve or vision.

Put simply, Ocular Hypertension is a risk condition—not a disease.

Because there is no permanent damage at this stage, regular monitoring is essential. Detecting early changes in the optic nerve or visual field allows treatment to begin before irreversible vision loss occurs.

Clinical Pearl

A single elevated eye pressure measurement is not enough to diagnose Ocular Hypertension. Intraocular pressure naturally fluctuates throughout the day (diurnal variation) and may also be influenced by factors such as corneal thickness, measurement technique, and other physiological variables.

Therefore, the diagnosis should be based on repeated IOP measurements, together with a comprehensive evaluation of the optic nerve, retinal nerve fiber layer, visual field, and anterior chamber angle.

Although most patients with Ocular Hypertension do not develop glaucoma in the short term, they should be considered an at-risk population and undergo regular follow-up examinations. This is particularly important for individuals with additional risk factors, such as thin central corneal thickness (CCT), older age, or suspicious optic nerve findings, all of which increase the likelihood of developing Primary Open-Angle Glaucoma (POAG) over time.

Reference: European Glaucoma Society. Terminology and Guidelines for Glaucoma. 6th Edition. 2025.

Topic 2 Can High Eye Pressure Turn into Glaucoma?

Does Everyone with Ocular Hypertension Develop Glaucoma?

The way we manage Ocular Hypertension (OHT) has changed dramatically over the past two decades. Instead of treating every patient with elevated eye pressure, today's approach focuses on assessing each individual's risk before deciding whether treatment is necessary.

This change was largely driven by one of the most influential studies in glaucoma research—the Ocular Hypertension Treatment Study (OHTS).

The Ocular Hypertension Treatment Study (OHTS)

The Ocular Hypertension Treatment Study (OHTS) is considered one of the landmark studies in glaucoma research.

A landmark study is a research study that significantly changes medical knowledge or clinical practice. Its findings are highly influential and are widely incorporated into clinical guidelines and everyday patient care.

OHTS fundamentally changed the way ophthalmologists approach patients with Ocular Hypertension by demonstrating that not every patient with elevated eye pressure requires immediate treatment.

Study Design

OHTS was a multicenter randomized clinical trial, which means the study was conducted across multiple medical centers, and participants were randomly assigned to different treatment groups.

This type of study design is considered one of the highest levels of clinical evidence because it helps minimize bias and ensures that the results are reliable and applicable to a broad range of patients.

A total of 1,636 patients with Ocular Hypertension were enrolled and randomly assigned to one of two groups:

• Treatment group: Received topical intraocular pressure-lowering eye drops.

• Observation group: Received no immediate treatment and was closely monitored.

The treatment goal was to:

• Reduce intraocular pressure to below 24 mmHg, and

• Achieve at least a 20% reduction from baseline IOP.

The primary outcome was the development of Primary Open-Angle Glaucoma (POAG), defined by either:

• Reproducible glaucomatous visual field defects, or

• Characteristic glaucomatous changes of the optic nerve.

Key Findings

The study demonstrated that treatment effectively lowered intraocular pressure by an average of 22.5%, whereas eye pressure decreased by only about 4% in the observation group.

After five years of follow-up:

• 4.4% of patients in the treatment group developed glaucoma.

• 9.5% of patients in the observation group developed glaucoma.

In other words, lowering intraocular pressure reduced the risk of developing glaucoma by approximately 50%.

However, one of the most important findings is often overlooked:

More than 90% of untreated patients did not develop glaucoma during the first five years of follow-up.

This finding highlights that elevated eye pressure alone does not mean a patient will inevitably develop glaucoma.

Long-Term Follow-up (OHTS II)

The long-term extension of the study (OHTS II) followed participants for approximately 13 years.

The investigators found that:

• About 16% of patients who received early treatment developed glaucoma.

• Approximately 22% of patients whose treatment was delayed developed glaucoma.

Interestingly, among patients who were considered low risk at baseline, delaying treatment did not significantly increase the risk of developing glaucoma.

These findings reinforced the concept that treatment decisions should be based on an individual's overall risk profile rather than eye pressure alone.

Major Risk Factors Identified by OHTS

OHTS identified several factors that increase the likelihood of developing Primary Open-Angle Glaucoma:

• Thin central corneal thickness (CCT)

• Higher intraocular pressure (IOP)

• Older age

• Larger vertical cup-to-disc ratio

• Higher visual field Pattern Standard Deviation (PSD)

• Optic disc hemorrhage

These factors are now routinely considered when assessing glaucoma risk in patients with Ocular Hypertension.

An Interesting Finding

Another important observation from OHTS was how glaucoma was first detected.

Among patients who eventually developed glaucoma:

• Approximately 50% were first diagnosed based on changes in optic disc photographs.

• Around 40% were first identified through visual field testing.

This finding highlights an important clinical message:

No single test is sufficient for glaucoma monitoring. A comprehensive follow-up should include evaluation of the optic nerve, retinal nerve fiber layer, visual field testing, and intraocular pressure.

Key Messages from OHTS

The Ocular Hypertension Treatment Study transformed the management of Ocular Hypertension and established several important principles:

• Not all patients with Ocular Hypertension have the same risk of developing glaucoma.

• Lowering intraocular pressure significantly reduces the risk of glaucoma.

• However, immediate treatment is not necessary for every patient.

• The most important step is to assess each patient's individual risk before making treatment decisions.

Today, this risk-based approach has become the cornerstone of modern glaucoma care and forms the basis of recommendations in major international clinical guidelines, including those from the European Glaucoma Society (EGS) and the American Academy of Ophthalmology (AAO).

Topic 3 How Is Your Risk Assessed?

Risk Assessment: Why Doctors Don't Rely on Eye Pressure Alone

The modern approach to managing patients with Ocular Hypertension (OHT)—a condition in which eye pressure is elevated but glaucoma has not yet developed—is based on individualized risk assessment, rather than intraocular pressure (IOP) alone.

Scientific evidence has shown that two patients with similar eye pressure may have very different risks of developing glaucoma. While one person may never develop optic nerve damage, another may progress to glaucoma despite having a similar IOP. This is why eye pressure is considered an important risk factor, but not the only factor that determines whether glaucoma will develop.

Based on data from the Ocular Hypertension Treatment Study (OHTS), researchers developed the OHT Risk Calculator, a tool that estimates an individual's 5-year risk of developing Primary Open-Angle Glaucoma (POAG). Today, this calculator is widely used in clinical practice and has been incorporated into several international glaucoma guidelines to help ophthalmologists decide whether treatment should be started or whether careful observation is sufficient.

What makes the OHT Risk Calculator more accurate than relying on eye pressure alone is that it considers multiple clinical risk factors simultaneously, recognizing that glaucoma develops through the interaction of several factors rather than elevated IOP alone.

What Factors Does the OHT Risk Calculator Consider?

The calculator uses several clinical measurements that are routinely obtained during a comprehensive eye examination.

Age

Older age is associated with a higher risk of developing glaucoma because the optic nerve becomes more vulnerable to damage over time.

Intraocular Pressure (IOP)

Higher eye pressure places greater mechanical stress on the optic nerve and remains the most important modifiable risk factor for glaucoma. However, it is only one part of the overall risk assessment.

Central Corneal Thickness (CCT)

The OHTS identified thin central corneal thickness as one of the strongest predictors of glaucoma development. Patients with thinner corneas have a higher risk of developing POAG than those with thicker corneas. This may be partly because thin corneas can lead to underestimation of the true eye pressure, but they may also reflect a structurally more susceptible eye.

Vertical Cup-to-Disc Ratio

Patients with a larger vertical cup-to-disc ratio at baseline are more likely to develop glaucomatous optic nerve damage over time, even if they do not currently meet the diagnostic criteria for glaucoma.

Visual Field Pattern Standard Deviation (PSD)

The Pattern Standard Deviation (PSD) is a measurement obtained during visual field testing that helps detect subtle, early abnormalities. A higher PSD may indicate an increased risk of future glaucoma, even when the overall visual field appears normal.

By combining all of these factors, the OHT Risk Calculator estimates a patient's probability of developing Primary Open-Angle Glaucoma within the next five years, allowing treatment decisions to be based on scientific evidence rather than eye pressure alone.

The OHT Risk Calculator

The OHT Risk Calculator was developed using data from the Ocular Hypertension Treatment Study (OHTS) and is freely available through the Washington University School of Medicine.

OHT Risk Calculator:https://ohts.wustl.edu/risk/

The calculator provides an estimated 5-year percentage risk of developing Primary Open-Angle Glaucoma, helping ophthalmologists and patients make informed treatment decisions together through shared decision-making.

How Is the Risk Calculated?

The OHT Risk Calculator offers two methods of estimating risk.

1. Continuous Method

This method uses the patient's actual clinical measurements, including age, intraocular pressure, central corneal thickness, and optic nerve findings. Because it analyzes continuous numerical data, it provides the most accurate and individualized risk estimate and is preferred in clinical practice and research.

2. Point System

The Point System is a simplified approach that converts clinical measurements into score categories. For example, age and eye pressure are grouped into ranges, with each range assigned a specific number of points. Although this method is less precise than the Continuous Method, it produces very similar results and is useful when a calculator is not readily available.

Interpreting the Results

Although there is no universally accepted cut-off value, clinicians generally classify patients into three risk categories based on their estimated 5-year risk of developing glaucoma.

Low Risk

Less than 5%

Most patients in this group do not require immediate treatment. Instead, regular monitoring with eye pressure measurements, optic nerve evaluation, OCT imaging, and visual field testing is usually appropriate.

Moderate Risk

Approximately 5–15%

Treatment decisions should be individualized by considering additional factors, including:

• Age and life expectancy

• Intraocular pressure

• Optic nerve appearance

• Central corneal thickness

• Family history of glaucoma

• Ability to attend regular follow-up visits

• Patient preferences and concerns

Some patients may benefit from early treatment, while others can be safely monitored.

High Risk

Greater than 15%

Patients in this category are generally recommended to begin treatment to reduce intraocular pressure because they have a substantially higher likelihood of developing Primary Open-Angle Glaucoma. Initial treatment may include pressure-lowering eye drops or Selective Laser Trabeculoplasty (SLT), depending on the patient's individual circumstances and preferences.

Clinical Pearl The most important contribution of the Ocular Hypertension Treatment Study (OHTS) was not simply the development of a risk calculator—it fundamentally changed the way ophthalmologists manage patients with Ocular Hypertension. Rather than treating everyone with elevated eye pressure, modern glaucoma care focuses on treating patients who are at the greatest risk of developing glaucoma. This risk-based approach has become a cornerstone of contemporary glaucoma management and reflects the principles of personalized, evidence-based medicine.

Topic 4 When Should Treatment Start?

Once a patient is identified as having a high risk of developing glaucoma, treatment may be recommended. The primary goal is to lower intraocular pressure (IOP) in order to reduce the risk of future optic nerve damage and preserve vision over the long term.

Today, two main treatment options are commonly used.

1. Pressure-Lowering Eye Drops

Eye drops remain the most widely used first-line treatment for Ocular Hypertension. Depending on the type of medication, they work by either:

• reducing the production of aqueous humor (the fluid inside the eye),

• increasing its drainage, or

• both.

By lowering intraocular pressure, these medications help reduce the risk of developing glaucoma.

2. Selective Laser Trabeculoplasty (SLT)

Selective Laser Trabeculoplasty (SLT) is a laser procedure that improves the eye's natural drainage system by stimulating the trabecular meshwork, allowing aqueous humor to drain more efficiently. As a result, intraocular pressure decreases without the need for incisional surgery.

SLT is a minimally invasive procedure, is performed in the outpatient clinic, and can often reduce or even eliminate the need for long-term glaucoma medications in selected patients.

Choosing the Right Treatment

For most patients with Ocular Hypertension, treatment usually begins with the least invasive options, such as pressure-lowering eye drops or SLT. The choice of treatment depends on several factors, including the patient's risk of developing glaucoma, age, lifestyle, medical history, and personal preferences.

Rather than adopting a one-size-fits-all approach, treatment should be individualized to achieve the best long-term outcome for each patient.

The LiGHT Trial: A Landmark Study on First-Line Treatment

Another landmark study that has influenced modern glaucoma management is the LiGHT Trial (Laser in Glaucoma and Ocular Hypertension Trial).

This large multicenter randomized clinical trial conducted in the United Kingdom compared two initial treatment strategies for patients with Primary Open-Angle Glaucoma (POAG) and Ocular Hypertension:

• Starting treatment with pressure-lowering eye drops

• Starting treatment with Selective Laser Trabeculoplasty (SLT)

The study found that SLT was as effective as eye drops in controlling intraocular pressure, while allowing many patients to remain drop-free for several years.

In addition, patients who received SLT as their initial treatment were less likely to require glaucoma medications in the future and achieved excellent long-term IOP control.

These findings have led to a significant change in clinical practice. Today, several international guidelines—including those from the European Glaucoma Society (EGS) and the National Institute for Health and Care Excellence (NICE)—recommend SLT as a first-line treatment option for appropriately selected patients with Ocular Hypertension and Primary Open-Angle Glaucoma.

Clinical Pearl The choice between eye drops and SLT is not about which treatment is "better" for everyone. Instead, the best treatment is the one that matches the patient's individual risk profile, lifestyle, treatment goals, and personal preferences. Modern glaucoma care emphasizes shared decision-making, ensuring that patients and their ophthalmologists work together to choose the most appropriate treatment strategy.

Topic 5 What Is the Goal of Treatment?

According to the Ocular Hypertension Treatment Study (OHTS), the initial goal of treatment for patients with Ocular Hypertension is to lower intraocular pressure (IOP) by at least 20% from baseline while aiming to keep the IOP below 24 mmHg.

However, the true goal of treatment extends far beyond simply lowering a number on the eye pressure measurement.

The ultimate objective is to reduce the risk of developing glaucoma and prevent irreversible damage to the optic nerve.

The optic nerve is responsible for transmitting visual information from the eye to the brain. Once it is damaged, the vision that has been lost cannot be restored. This is why glaucoma is considered a chronic, progressive disease that can lead to permanent vision loss if left untreated.

For this reason, treatment is not focused solely on achieving a target eye pressure. Instead, the aim is to maintain the intraocular pressure at a level that is safe for each individual patient, based on their overall risk profile.

Equally important is regular monitoring of the optic nerve and visual field. Even when eye pressure appears well controlled, periodic examinations are essential to detect any early signs of disease progression.

Ultimately, successful management of Ocular Hypertension is about protecting the optic nerve, preventing the development of glaucoma, preserving vision, and maintaining quality of life over the long term.

Conclusion

Ocular Hypertension (OHT) is a condition in which the intraocular pressure (IOP) is higher than normal, but there is no evidence of optic nerve damage or visual field loss. Therefore, it does not meet the diagnostic criteria for glaucoma. Nevertheless, Ocular Hypertension is an important risk factor for developing Primary Open-Angle Glaucoma (POAG) and should not be overlooked.

Over the past two decades, landmark studies—most notably the Ocular Hypertension Treatment Study (OHTS)—have fundamentally changed the way ophthalmologists manage this condition. Rather than making treatment decisions based solely on eye pressure, today's approach focuses on individualized risk assessment. By considering multiple clinical factors, including age, intraocular pressure, central corneal thickness, optic nerve appearance, and visual field findings, clinicians can better estimate each patient's likelihood of developing glaucoma and tailor treatment accordingly.

Patients at higher risk may benefit from early treatment with pressure-lowering eye drops or Selective Laser Trabeculoplasty (SLT) to reduce the risk of future glaucoma. In contrast, patients at lower risk may not require immediate treatment but should undergo regular follow-up examinations to monitor for any changes in the optic nerve or visual field.

Most importantly, the goal of treatment is not simply to lower eye pressure. The real objective is to protect the optic nerve, preserve vision, and maintain quality of life over the long term. Treatment decisions should therefore be based on the best available scientific evidence while taking into account each patient's individual risk factors, overall health, lifestyle, and personal preferences.

If you have been told that "your eye pressure is high, but you do not have glaucoma," there is no need to panic—but it is equally important not to ignore the diagnosis. Regular eye examinations, appropriate risk assessment, and timely intervention when necessary remain the most effective strategies for preventing glaucoma-related vision loss.

Take-Home Message We do not treat the eye pressure—we treat the patient's risk. The true purpose of managing Ocular Hypertension is not simply to lower a number on the tonometer, but to protect the optic nerve, preserve vision, and maintain lifelong visual function. This risk-based, individualized approach has become the cornerstone of modern glaucoma care.

Reference

1. Ocular Hypertension Treatment Study (OHTS)

Kass, M. A., Heuer, D. K., Higginbotham, E. J., Johnson, C. A., Keltner, J. L., Miller, J. P., Parrish, R. K., Wilson, M. R., & Gordon, M. O. (2002).The ocular hypertension treatment study: A randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Archives of Ophthalmology, 120(6), 701–713. https://doi.org/10.1001/archopht.120.6.701

2. European Glaucoma Society Guideline (6th edition)

European Glaucoma Society. (2025).European glaucoma society terminology and guidelines for glaucoma (6th ed.). PubliComm.

3. LIGHT Trial

Gazzard, G., Konstantakopoulou, E., Garway-Heath, D., Garg, A., Vickerstaff, V., Hunter, R., Ambler, G., Bunce, C., Wormald, R., Nathwani, N., Barton, K., Rubin, G., Morris, S., & King, A. (2019).Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): A multicentre randomised controlled trial. The Lancet, 393(10180), 1505–1516. https://doi.org/10.1016/S0140-6736(18)32213-X

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