Understanding Glaucoma: Causes of Blindness and Early Detection

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• What is Glaucoma? A Neurodegenerative Eye Disease
• What Causes Blindness in Glaucoma?
• First Symptoms of Glaucoma: Why It's a Silent Thief
• The Critical Importance of Glaucoma Screening
• How Glaucoma is Diagnosed: Pressure, Imaging, and Visual Fields
• Family History and Other Glaucoma Risk Factors
• Preventing Blindness from Glaucoma

What is Glaucoma? A Neurodegenerative Eye Disease

Glaucoma is fundamentally a neurodegenerative disease of the eye, not merely a condition of high pressure. As Dr. Francesca Cordeiro, MD, clarifies, increased intraocular pressure is a significant risk factor that modulates the disease but is not its root cause. The condition involves the progressive death of specific nerve cells in the retina, leading to irreversible vision loss over time. This modern understanding shifts the focus from pressure management to neuroprotection.

What Causes Blindness in Glaucoma?

Blindness in glaucoma results from the death of retinal ganglion cells. Dr. Francesca Cordeiro, MD, explains that these specialized nerve cells are responsible for transmitting visual information from the eye to the brain. As these cells die over time due to the disease process, they create permanent blind spots in a person's field of vision. These spots gradually enlarge and coalesce, ultimately leading to significant visual disability and, in advanced cases, complete blindness.

First Symptoms of Glaucoma: Why It's a Silent Thief

Glaucoma is notoriously asymptomatic in its early stages, earning it the nickname "the silent thief of sight." Dr. Francesca Cordeiro, MD, notes that patients typically notice nothing wrong initially. This is because the brain employs sophisticated compensatory mechanisms to "fill in" the missing patches of vision caused by dying retinal cells. A person may be completely unaware of their peripheral vision loss until the damage is severe and central vision is affected, often only discovered through a screening test.

The Critical Importance of Glaucoma Screening

Because glaucoma has no early symptoms, proactive screening is the only way to detect the disease before major vision loss occurs. Dr. Francesca Cordeiro, MD, emphasizes that this is crucial for preventing blindness. The asymptomatic nature of glaucoma has real-world consequences; research shows patients with glaucoma have a higher incidence of traffic accidents because their brain may fill in a blind spot, causing them to miss hazards like a child running into the road. Regular eye exams are essential for early intervention.

How Glaucoma is Diagnosed: Pressure, Imaging, and Visual Fields

Diagnosing glaucoma involves a multi-faceted approach. As Dr. Cordeiro outlines, an optometrist or ophthalmologist will measure eye pressure, though this is not a definitive diagnostic criterion. They also examine the back of the eye with an ophthalmoscope to assess the health of the optic nerve for signs of damage. Imaging tests measure the thickness of the optic nerve fiber layer. The functional gold standard, however, is the visual field test, where a patient presses a button when they see lights flash in their peripheral vision to map out any blind spots.

Family History and Other Glaucoma Risk Factors

A primary risk factor for developing glaucoma is a family history of the disease. Dr. Francesca Cordeiro, MD, states that first-degree relatives of a glaucoma patient are at a much greater risk. This is why many healthcare systems offer free sight tests to these individuals. While high eye pressure is a major modifiable risk factor, other factors include advanced age, certain medical conditions like diabetes, and extreme nearsightedness. Understanding these risks helps identify who should be most vigilant about screening.

Preventing Blindness from Glaucoma

The goal of glaucoma treatment is to prevent blindness by slowing or halting the progression of the disease. As Dr. Francesca Cordeiro, MD, explains, this requires patients to see an ophthalmologist early, long before symptoms appear. While existing vision loss cannot be reversed, current treatments—including prescription eye drops, laser therapy, and surgery—aim to lower eye pressure and protect the remaining retinal ganglion cells from dying. Early detection through regular screening is the most powerful tool for preserving vision and maintaining quality of life.

Full Transcript

Dr. Francesca Cordeiro, MD: Glaucoma is often defined as high pressure in the eye, but it is not the cause of glaucoma. Increased eye pressure is merely an associated risk factor that affects the disease. Glaucoma is a neurodegenerative disease. Nerve cells in the retina start to die.

Dr. Anton Titov, MD: Let's start the conversation with glaucoma. Glaucoma results in increased pressure in the eye. It is often a silent eye disease until patients go blind. When patients with glaucoma develop blindness, it's a significant disability. What is responsible for causing blindness in glaucoma when pressure in the eye is increased?

Dr. Francesca Cordeiro, MD: The concept of high pressure being the cause of glaucoma has changed over time. We now say that pressure being elevated in the eyes is a risk factor. It's not a criterion for diagnosis of glaucoma. We think now that glaucoma is more of a neuropathy. It’s a nerve eye disease. The eye pressure can modulate how the patient is affected.

What happens is this: the nerve cells of the eye are specialized. These nerve cells are called the retinal ganglion cells. These are the cells that die over time in glaucoma. That's what leads to vision loss that develops in glaucoma.

Dr. Anton Titov, MD: How does blindness develop in glaucoma? What are the first symptoms that patients with glaucoma notice? What are the symptoms that patients notice if they are having this increased pressure in the eye?

Dr. Francesca Cordeiro, MD: The thing about glaucoma is there are no symptoms. That's why it's called the silent thief of sight. Patients don't recognize they have glaucoma because there's no way of knowing you have it. Your brain compensates. Special compensatory mechanisms are filling in that we know a lot more of nowadays.

What that means is where you cannot see things, the brain patches missing information. The brain fills up those patches of lost vision. As a patient, you wouldn't know you have the eye disease. That's one of the reasons why there is increasing evidence for traffic accidents. Patients with glaucoma are involved in road traffic accidents more often.

There's great research being done around the world. This shows quite clearly the fact that because your brain is filling things in, you may miss a child running through a road. Sometimes it happens to be in one of the areas that your brain has filled in, but you have not actually been able to see.

What has to be done when you're talking about an eye disease that is asymptomatic and silent? You have to find ways of picking it up for the patient. That is where screening for glaucoma comes in. In this country, one of the things that is offered to patients is glaucoma screening.

We know that if you have a family history of the eye disease, you are at much greater risk of glaucoma than if you didn't. Especially if you're a first-degree relative with glaucoma. Those patients who have first-degree relatives with glaucoma are offered free sight tests.

What the sight tests do, in addition to measuring pressure—increased eye pressure is a risk factor for glaucoma, but it's not actually a diagnostic criterion—is they look to see if there are nerve changes at the back of the eye. You may be familiar with this. When you're going to the optician or your optometrist, they look at the back of your eye. They use the ophthalmoscope and go very close to your eye.

What they are looking at there is the visible structures of the nerve, the optic nerve that supplies vision. The optometrist sees if there's any damage to the back of the eye. In addition to that, they will do some imaging.

Physicians will look to see if the optic nerve fiber layer of your eye is thinned. Ophthalmologists will also do what is called a visual field test. The visual field test still is the gold standard function test for glaucoma.

It's a little bit like playing a Space Invaders game. You're positioned in a globe, and the machine lights up at different places around this globe randomly. You rely on the patient pressing the button every time that they are aware of light, some light that's flashing or coming into their field of vision.

Those ways of screening for the eye disease are the way we try to detect glaucoma. But it is very difficult to detect glaucoma. Often this is the real issue that we have. Patients present, more than anything else, with a loss of vision.

In other words, you're already a long way down this decline of your vision loss. Patients are much nearer to blindness than if you had a symptomatic eye disease.

Dr. Anton Titov, MD: You should be presenting to your ophthalmologist much earlier. Then you will possibly have better chances of stopping blindness occurring in the first place.