Glaucoma Beyond Eye Pressure: Understanding a Neurodegenerative Disease

Host: Welcome back to the show. Today we're tackling a condition that affects more than 80 million people worldwide and remains the leading cause of irreversible blindness. But the way we understand it has been shifting in some really fascinating ways. Joining me is Dr. Saikumar Gandapodi from the Netra Eye Institute. Dr. Gandapodi, thank you for being here.
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Dr. Gandapodi: Thank you for having me. It's a pleasure. Glaucoma is something I've spent a good part of my career on, and the topic you've chosen is close to my heart, because I think it represents where the field is genuinely headed.
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Host: Let's start there. For most people, including many patients, glaucoma equals "high eye pressure." Is that wrong?
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Dr. Gandapodi: Not wrong, but incomplete. For decades we treated intraocular pressure, or IOP, as essentially synonymous with glaucoma. And there's good reason for that. Elevated pressure is the single most important modifiable risk factor we know of, and lowering it is still the only proven way to slow the disease. So I never want to dismiss it. But here's the puzzle that's reshaped our thinking: a significant proportion of patients develop glaucoma with completely normal pressures. We call it normal-tension glaucoma. And conversely, many people walk around with high pressure their entire lives and never lose a single nerve fiber. So if pressure were the whole story, neither of those groups should exist.
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Host: So the pressure is a clue, not the whole crime.
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Dr. Gandapodi: That's a lovely way to put it. Exactly. What's actually dying in glaucoma is a population of cells called retinal ganglion cells. These are the neurons that carry visual information from the eye to the brain. Their axons bundle together to form the optic nerve. When we say someone is going blind from glaucoma, what we really mean is that these neurons are progressively dying. And that reframes the entire disease. Glaucoma isn't fundamentally a plumbing problem in the eye. It's a neurodegenerative disease, in the same broad family as Alzheimer's or Parkinson's.
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Host: That's a striking comparison. Can you unpack it?
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Dr. Gandapodi: Sure. In Alzheimer's, neurons in the brain die through a cascade of mechanisms: protein misfolding, inflammation, energy failure in the cells, oxidative stress. What we've discovered is that the retinal ganglion cells in glaucoma die through remarkably similar pathways. There's growing evidence of mitochondrial dysfunction, meaning the cell's energy factories start failing. There's oxidative stress, where damaging molecules accumulate. There's neuroinflammation, where the eye's own immune cells turn against the neurons. And some researchers have even found deposits of the same proteins implicated in Alzheimer's. So at the cellular level, the optic nerve is behaving like a piece of brain tissue that is degenerating.
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Host: And the eye is technically part of the central nervous system, isn't it?
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Dr. Gandapodi: Precisely. Embryologically, the retina and optic nerve develop as outgrowths of the brain. The optic nerve is myelinated by the same type of cells you find in the brain, not the ones in peripheral nerves. So when I tell patients the eye is a window to the brain, I mean it almost literally. The retinal ganglion cell is a brain neuron that happens to live in the eye.
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Host: So let's go back to pressure for a moment. If glaucoma is multifactorial, why does pressure still matter so much?
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Dr. Gandapodi: Because pressure is one of the major stressors that pushes these vulnerable neurons over the edge. Think of the optic nerve head, where all those axons funnel out of the eye through a sieve-like structure called the lamina cribrosa. Elevated pressure causes mechanical stress and deformation at that point. It can pinch the axons, impair the transport of essential molecules up and down the nerve fiber, and reduce blood flow. So pressure is a real and important insult. But it's acting on cells whose survival depends on many other factors. Lower the pressure and you reduce one major stressor. But if the other factors are unfavorable, the neurons can keep dying anyway. That's exactly what we see clinically: patients whose pressure we've controlled beautifully who continue to progress.
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Host: What are those other factors? You mentioned blood flow.
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Dr. Gandapodi: Vascular health is a big one. The optic nerve is metabolically hungry and depends on a steady, well-regulated blood supply. We see strong associations between glaucoma and conditions like low blood pressure, especially nocturnal dips where pressure falls too far at night, migraine, and a phenomenon called vascular dysregulation, where the small vessels don't respond properly to the body's needs. There's a well-known link with cold hands and feet, what's sometimes called Flammer syndrome, which seems to identify a subset of patients whose vessels are overly reactive. For these patients, perfusion of the optic nerve is unstable, and that instability appears to damage the neurons independent of pressure.
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Host: So blood pressure that's too low can actually be bad for the eyes? That's counterintuitive.
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Dr. Gandapodi: It surprises people, yes. We spend so much public health energy worrying about high blood pressure that the idea of pressure being too low for the optic nerve feels strange. But what the nerve needs is something called perfusion pressure, essentially the difference between the blood pressure pushing blood into the eye and the eye pressure resisting it. If systemic blood pressure drops too low, particularly during sleep, perfusion to the nerve can fall to dangerous levels. This is why I'm cautious with patients who are on aggressive blood pressure medication taken at night. Sometimes a well-meaning cardiology regimen can have unintended consequences for the optic nerve.
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Host: That's a fascinating example of how interconnected the body is. What else feeds into this multifactorial picture?
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Dr. Gandapodi: Genetics is enormous and increasingly well mapped. We've identified numerous genes associated with glaucoma. Some affect the drainage structures and therefore pressure. But many others affect things like mitochondrial function, the structural integrity of the optic nerve head, and how neurons handle stress. Then there's age, which is the strongest non-modifiable risk factor, partly because aging neurons are simply less resilient. There's a strong genetic and racial dimension too. People of African ancestry develop glaucoma earlier and more severely, while certain forms like angle-closure glaucoma are more common in East Asian populations. Family history matters enormously. And then there are emerging contributors we're still characterizing, like the role of cerebrospinal fluid pressure behind the eye, sleep apnea, and even the gut microbiome's influence on inflammation.
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Host: Sleep apnea and glaucoma. Walk me through that.
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Dr. Gandapodi: Sleep apnea causes repeated episodes of low oxygen throughout the night, along with surges and crashes in blood pressure. For a tissue as sensitive to oxygen and perfusion as the optic nerve, that's a hostile environment. Studies have found higher rates of glaucoma among people with untreated sleep apnea. It fits perfectly into the multifactorial model: it's not pressure in the eye, it's a systemic condition creating oxidative and vascular stress that the neurons ultimately pay for. And it's a good reminder that managing glaucoma sometimes means looking well beyond the eye.
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Host: This raises an obvious question. If glaucoma is multifactorial and neurodegenerative, why are nearly all our treatments still aimed at pressure?
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Dr. Gandapodi: It's the honest tension in our field right now. Lowering pressure, whether with eye drops, lasers, or surgery, remains the only intervention proven in large trials to slow progression. And it genuinely works for many patients. So it would be irresponsible to abandon it. But you're right that it addresses only one node in a complex network. The frontier of research is what we call neuroprotection: treatments that protect the neurons directly, regardless of pressure. The dream is a therapy that keeps retinal ganglion cells alive even when other stressors are at play.
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Host: Where does that research stand?
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Dr. Gandapodi: It's promising but humbling. Various approaches are being explored. There are agents aimed at supporting mitochondrial function, including something as simple as nicotinamide, a form of vitamin B3, which in early studies showed some benefit to optic nerve function. There's work on neurotrophic factors, which are essentially survival signals for neurons. There's research into reducing the neuroinflammation I mentioned. And further out, there's regenerative medicine: stem cell approaches and even gene therapy attempting to protect or eventually replace lost neurons. I want to be measured here, because the history of neuroprotection in glaucoma is littered with therapies that looked exciting in the lab and failed in human trials. The retinal ganglion cell is stubborn to protect. But the momentum and the science are better than they've ever been.
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Host: The nicotinamide finding is interesting because it's so accessible. Should people be running out to take vitamin B3?
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Dr. Gandapodi: I get this question a lot, and I'd urge caution. The early results are encouraging and have generated real excitement, but we're talking about specific doses studied in controlled settings, and larger definitive trials are still underway. It is not yet standard of care, and high doses of any supplement carry their own considerations. So my answer is: talk to your ophthalmologist, don't self-prescribe based on a headline, and let the evidence mature. But I do find it heartening that one of the more promising leads is something so fundamental to cellular energy. It reinforces the whole metabolic, neurodegenerative framework we've been discussing.
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Host: Let's talk about what this reframing means for patients practically. If you're a patient hearing this for the first time, what should change in how you think about your glaucoma?
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Dr. Gandapodi: A few things. First, it should reinforce why adherence to pressure-lowering treatment matters, because that's still our best tool, and we see far too many patients stop their drops because the disease is silent and they feel fine. Second, it should broaden the conversation to overall health. Your blood pressure, your sleep, your cardiovascular fitness, whether you smoke, your management of conditions like diabetes and sleep apnea, these all plausibly influence the health of your optic nerve. Glaucoma care is increasingly whole-body care. And third, it should bring hope. Understanding glaucoma as neurodegeneration opens doors to entirely new categories of treatment that simply weren't conceivable when we thought of it purely as an eye-pressure problem.
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Host: You mentioned the disease is silent. That's one of the cruel features of glaucoma, isn't it?
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Dr. Gandapodi: It's the cruelest part. Glaucoma typically attacks peripheral vision first and does so painlessly and gradually. The brain is remarkably good at filling in the gaps, so patients often don't notice until they've lost a substantial amount of vision, sometimes irreversibly. By the time someone says, "I think my vision has changed," significant nerve damage may already have occurred. This is why screening is so vital, especially for anyone with risk factors: family history, older age, African or Asian ancestry, high pressure, or being very nearsighted. A simple eye exam can catch it long before symptoms appear. I cannot overstate this. The vision you lose to glaucoma does not come back, but the vision you still have can almost always be protected if we catch the disease in time.

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Host: Does the neurodegenerative framework change how you detect the disease, not just treat it?
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Dr. Gandapodi: Increasingly, yes. Our imaging has become extraordinary. With optical coherence tomography, we can measure the thickness of the nerve fiber layer down to microns and detect cell loss before the patient notices any visual change. That's essentially watching neurodegeneration in real time. There's also exciting research using the eye as a window to detect brain neurodegeneration more broadly. Because the retina is accessible brain tissue, some researchers believe retinal imaging may one day help screen for conditions like Alzheimer's. So the relationship runs both ways: brain science informs how we understand glaucoma, and the glaucomatous eye may teach us about the brain.
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Host: That's a remarkable note. We're nearly out of time, so let me ask you to look ahead. Where do you hope this field is in ten or fifteen years?
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Dr. Gandapodi: My hope is that we move from a single-target disease to a personalized, multi-target one. I imagine a future where we assess each patient's particular combination of risk factors, their pressure, yes, but also their vascular profile, their genetics, their metabolic and inflammatory status, and we tailor a combination of therapies accordingly. Pressure-lowering for those who need it, neuroprotection for the neurons, vascular support where perfusion is the problem. And ultimately, I'd love to see regenerative approaches restore at least some of what's been lost, which would be revolutionary, since irreversibility has defined this disease for all of history. We're not there yet. But the shift from thinking of glaucoma as a pressure problem to understanding it as a complex neurodegenerative disease is the conceptual leap that makes all of that possible.
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Host: Dr. Saikumar Gandapodi of the Netra Eye Institute, this has been genuinely illuminating. Thank you for helping us see glaucoma in a completely new light.
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Dr. Gandapodi: Thank you. And if listeners take away just one thing, let it be this: get your eyes checked, even when they feel perfectly fine. It's the simplest thing you can do to protect a lifetime of sight.
Host: Wonderful advice to end on. Thanks to all of you for listening, and we'll see you next time.