Causes of Glaucoma
The causes of glaucoma vary depending on the specific type of the condition. At its core, glaucoma is linked to damage of the optic nerve, often—but not always—caused by elevated intraocular pressure. Understanding what leads to increased pressure, as well as what can damage the optic nerve in normal-tension cases, is key to recognising risks and preventing sight loss.
Although many factors contribute to the development of glaucoma, most involve the build-up of fluid in the eye, poor drainage, or damage from compromised blood supply. Genetics and systemic health conditions also play significant roles.
Eye Fluid Dynamics
The eye continuously produces a fluid called aqueous humour, which:
Nourishes the eye tissues
Maintains proper pressure inside the eye
Drains through the trabecular meshwork at the drainage angle between the iris and cornea
When this drainage system becomes blocked or inefficient, fluid builds up, leading to:
Increased intraocular pressure (IOP)
Compression of the optic nerve fibres
Gradual death of nerve cells responsible for vision
This process is central to primary open-angle glaucoma, the most common form of the disease.
Causes of Different Types of Glaucoma
1. Primary Open-Angle Glaucoma
This is usually caused by:
Age-related changes in the eye’s drainage system
Resistance to fluid outflow, even though the angle is open
Genetic mutations affecting pressure regulation
While eye pressure increases slowly, it eventually reaches a level that damages the optic nerve. Some people with high eye pressure never develop nerve damage, while others with normal pressure can develop glaucoma.
2. Angle-Closure Glaucoma
This occurs when:
The iris bulges forward, narrowing or blocking the drainage angle
Fluid builds up rapidly, causing a sudden spike in IOP
The eye cannot drain fluid quickly enough, creating acute symptoms
Common triggers include:
Pupil dilation in low light
Certain medications
Hyperopia (farsightedness), which can alter eye anatomy
This type is more common in women, older adults, and people of Asian descent.
3. Normal-Tension Glaucoma
In these cases, optic nerve damage occurs despite normal eye pressure. Possible causes include:
Poor blood flow to the optic nerve
Vascular conditions like low blood pressure or Raynaud’s disease
Genetic factors
Structural vulnerability of the optic nerve
This form is more common in people of Japanese ancestry and those with a family history of glaucoma.
4. Congenital Glaucoma
This rare form occurs in infants and young children. Causes include:
Malformation of the drainage system during development
Genetic defects affecting eye growth
Inherited mutations passed from parents
Early surgical treatment is often required to preserve vision.
5. Secondary Glaucoma
Secondary glaucoma results from another condition that interferes with fluid drainage or increases pressure. Causes include:
Eye trauma or surgery
Inflammatory eye diseases (e.g. uveitis)
Steroid medications
Diabetes, which can cause neovascular glaucoma
Tumours or lens dislocation
Managing the underlying condition is essential for treating this form of glaucoma.
Genetic and Family Factors
Genetics play a significant role in all types of glaucoma. Those with a family history—especially first-degree relatives—are at four to nine times greater risk of developing the disease.
Specific genes linked to glaucoma include:
MYOC – associated with juvenile open-angle glaucoma
OPTN and TBK1 – linked to normal-tension glaucoma
CYP1B1 – associated with congenital glaucoma
Because of the genetic link, screening and early testing are advised for relatives of diagnosed patients.
Systemic Conditions That Increase Risk
Certain systemic illnesses and lifestyle factors can contribute to glaucoma:
Diabetes mellitus
Hypertension or hypotension
Obstructive sleep apnoea
Migraine
Use of steroids (oral, inhaled, or topical)
Smoking and poor cardiovascular health
These conditions may either raise eye pressure or reduce blood supply to the optic nerve.
Environmental and Behavioural Factors
While less clearly established, other potential contributors include:
Chronic eye strain
Low oxygen levels at high altitudes
Excessive caffeine intake, which may raise IOP temporarily
Prolonged stress, affecting vascular tone
Though not direct causes, these factors may compound risk in already susceptible individuals.
Summary of Main Causes
| Glaucoma Type | Primary Cause |
| Open-Angle | Slow fluid drainage, age, genetics |
| Angle-Closure | Iris position, anatomy, sudden blockage |
| Normal-Tension | Poor blood flow, nerve vulnerability |
| Congenital | Developmental defects, genetic mutation |
| Secondary | Trauma, inflammation, medications |
Conclusion | Causes of Glaucoma
The causes of glaucoma are diverse and often interrelated. Elevated eye pressure, poor fluid drainage, genetic predisposition, and vascular problems all contribute to the development of this sight-threatening condition. Identifying risk factors early and understanding the underlying mechanisms allows for better prevention, early diagnosis, and timely treatment.
