Illustration of an eye with normal pressure but a damaged optic nerve, symbolizing normal-tension glaucoma.

Normal Eye Pressure, Hidden Threat: Understanding Normal-Tension Glaucoma

Jordan Keane in Health & Wellness December 2025 • 5 min read.

"Uncover the Surprising Prevalence and Characteristics of Primary Angle Closure Glaucoma with Normal Intraocular Pressure."

Glaucoma, often associated with elevated intraocular pressure (IOP), is a leading cause of irreversible blindness worldwide. However, a significant subset of glaucoma patients presents with normal IOP, a condition known as normal-tension glaucoma (NTG) or primary angle closure glaucoma with normal intraocular pressure. This article explores the complexities of NTG, shedding light on its prevalence, characteristics, and the importance of comprehensive eye examinations for early detection and management.

Primary angle closure glaucoma (PACG) occurs when the angle between the iris and cornea narrows, blocking fluid drainage and increasing eye pressure. In many cases, PACG is asymptomatic until significant damage has occurred, making early detection crucial. While elevated IOP is a hallmark of PACG, it's increasingly recognized that a substantial number of individuals with PACG exhibit normal IOP at their initial examination.

This article provides a comprehensive look into normal-tension glaucoma, drawing upon recent research to explain the condition, its risk factors, diagnostic challenges, and management strategies. It emphasizes the importance of regular eye exams, including gonioscopy, to identify angle closure and other subtle signs of glaucoma, even when eye pressure is within the normal range. By understanding the nuances of NTG, individuals can take proactive steps to protect their vision and prevent irreversible sight loss.

What is Normal-Tension Glaucoma?

Illustration of an eye with normal pressure but a damaged optic nerve, symbolizing normal-tension glaucoma.

Normal-tension glaucoma (NTG), also known as primary angle closure glaucoma with normal intraocular pressure, is a type of glaucoma in which damage to the optic nerve occurs despite having IOP within the normal statistical range. This challenges the traditional understanding of glaucoma as solely a pressure-related disease. While the exact cause of NTG is unknown, several factors are believed to contribute to its development.

It's essential to understand that "normal" IOP is a statistical concept. What is normal for one person may be damaging to another. Individuals with NTG often have optic nerves that are more susceptible to damage, even at pressures considered normal for the general population.

Vascular Factors: Reduced blood flow to the optic nerve may play a role in NTG. Conditions like migraines, Raynaud's phenomenon, and sleep apnea have been associated with an increased risk of NTG.
Optic Nerve Sensitivity: Some individuals have optic nerves that are inherently more vulnerable to damage from pressure, even within the normal range.
Anatomical Factors: Specific anatomical features of the eye, such as a narrow angle between the iris and cornea, may contribute to NTG.
Systemic Conditions: Certain systemic diseases, such as autoimmune disorders, may increase the risk of NTG.

Identifying NTG requires a comprehensive eye examination that includes more than just measuring eye pressure. Gonioscopy is a crucial diagnostic procedure that allows the eye doctor to visualize the angle between the iris and cornea, assessing whether it's open, narrowed, or closed. This is essential to rule out angle-closure glaucoma, even when IOP is normal.

The Importance of Early Detection and Comprehensive Eye Exams

Normal-tension glaucoma can be challenging to diagnose, as it often presents without the typical symptom of elevated eye pressure. This is why regular, comprehensive eye examinations are so important. These exams should include gonioscopy to evaluate the drainage angle, as well as optic nerve imaging and visual field testing to assess for any signs of glaucoma damage. Early detection and management of NTG can help prevent further vision loss and maintain quality of life. If you have any risk factors for glaucoma, such as a family history of the disease, it's especially important to have regular eye exams, even if your eye pressure is normal. Protecting your vision starts with proactive care.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

What is Normal-Tension Glaucoma (NTG) and how does it differ from glaucoma associated with high eye pressure?

Normal-Tension Glaucoma (NTG), also known as primary angle closure glaucoma with normal intraocular pressure, is a form of glaucoma characterized by optic nerve damage despite the Intraocular Pressure (IOP) being within the normal statistical range. This differs significantly from glaucoma typically associated with elevated IOP. In the traditional understanding of glaucoma, elevated eye pressure is a primary cause of optic nerve damage. However, NTG demonstrates that damage can occur even when IOP is considered normal. This highlights the complexity of the disease, where factors beyond IOP play a crucial role in its development and progression.

What are the primary risk factors associated with Normal-Tension Glaucoma, and what role do they play in the disease's development?

Several factors contribute to the development of Normal-Tension Glaucoma. Vascular factors are significant, with reduced blood flow to the optic nerve potentially playing a key role. Conditions such as migraines, Raynaud's phenomenon, and sleep apnea have been linked to an increased risk of NTG. Optic nerve sensitivity also matters; some individuals have optic nerves that are inherently more vulnerable to damage even with normal IOP. Anatomical factors, such as a narrow angle between the iris and cornea, can contribute, and systemic conditions like autoimmune disorders may increase the risk. These factors can act individually or together to make the optic nerve susceptible to damage.

Why is Gonioscopy a crucial diagnostic procedure for Normal-Tension Glaucoma, and what information does it provide?

Gonioscopy is a critical diagnostic tool in diagnosing Normal-Tension Glaucoma because it allows the eye doctor to visualize the angle between the iris and cornea. This angle is crucial for the drainage of fluid from the eye. Gonioscopy helps determine if the angle is open, narrowed, or closed. In the context of NTG, gonioscopy helps rule out Primary Angle Closure Glaucoma (PACG), even when IOP is within normal limits. If the angle is narrowed or closed, it could indicate PACG, a condition that can lead to elevated IOP, but can sometimes present with normal IOP, thereby assisting in accurate diagnosis and treatment planning.

How does Normal-Tension Glaucoma impact the traditional understanding of glaucoma, and what are the implications for diagnosis and treatment?

Normal-Tension Glaucoma challenges the traditional view of glaucoma being solely a pressure-related disease. This shifts the focus to multiple factors beyond IOP. The implications are significant; diagnosis requires a comprehensive approach that extends beyond just measuring IOP. This includes gonioscopy to assess the drainage angle, optic nerve imaging, and visual field testing. Treatment strategies for NTG may also need to be adapted, as simply lowering IOP might not be sufficient, and addressing other risk factors could become important. Early detection and management, through regular eye exams and comprehensive assessments, are crucial to preventing further vision loss and maintaining quality of life.

What steps can individuals take to protect their vision if they are at risk for Normal-Tension Glaucoma?

Individuals can take proactive steps to protect their vision by prioritizing regular, comprehensive eye examinations. These exams should include gonioscopy to evaluate the drainage angle, as well as optic nerve imaging and visual field testing. If there are risk factors, such as a family history of the disease, it is especially important to have regular eye exams, even if the eye pressure is normal. Lifestyle adjustments, such as managing vascular health and addressing systemic conditions like sleep apnea, may also be recommended. Early detection and management of NTG can help prevent further vision loss and maintain quality of life.