Glaucoma is a slowly progressive disease characterised by a rise in the pressure inside the eye. This pressure has nothing to do with the blood pressure your family doctor measures on your arm: it is measured during an eye examination, and the patient does not feel it.
This is the key point. Glaucoma takes away sight a little at a time, without symptoms, and by the time symptoms appear the damage has already been done. The optic nerve fibres compressed by the pressure die and do not regenerate. This is why glaucoma cannot be cured: it has to be diagnosed early and kept under control over time.
What glaucoma is and why it gives no symptoms
If it is not diagnosed in time, glaucoma progressively narrows the visual field: you no longer see “out of the corner of your eye”. The loss advances slowly over the years, up to the so-called tunnel vision, which is the last stage before blindness.
Prevention happens in the eye clinic, because only there can the eye pressure be measured and checked against normal values. After the age of 40 to 50, a yearly eye examination with pressure measurement is the simplest way to catch early glaucoma, or to rule it out. When the optic nerve is already damaged, treatment is still useful to stop progression, but it does not recover what has been lost.
How it is diagnosed: the tests I request
Measuring the pressure alone is not enough. My approach is to cross-check three tests and compare them over time with the previous ones: it is the serial comparison that tells whether the disease is stable or progressing.
The visual field
Computerised visual field testing measures the function of the optic nerve. A patient can have full visual acuity and already have significant visual field damage, because the part that is lost first is the peripheral one. The test is harmless, done in the clinic and takes a few minutes: the patient presses a button every time a light appears on an illuminated dome. The real value of this test lies in repetition: a single visual field is a snapshot, a series of visual fields shows whether treatment is working.
Pachymetry, the thickness of the cornea
Optical pachymetry measures the thickness of the cornea without contact. Average corneal thickness is around 540 microns, with a normal range of roughly 520 to 580. Tonometers give a number (16, 18, 20 millimetres of mercury) that must always be related to corneal thickness. A cornea thinner than average makes the measurement underestimate the real pressure; a thicker cornea makes it overestimate it. In practice: a reading of 22 mmHg on a very thick cornea may be within the normal range, while the same 22 mmHg on a thin cornea may correspond to a considerably higher real pressure, and becomes a finding to investigate. Conversion tables that take thickness into account exist. This is why pachymetry is requested for anyone who has, or may be at risk of, glaucoma.
OCT of the optic nerve
OCT is a non-invasive test that maps the anatomy of the structures of the eye. In glaucoma it focuses on the optic nerve head and makes it possible to quantify the nerve fibres present. Visual field and OCT are two sides of the same coin: OCT tells how many fibres there are, the visual field tells whether they work. When the damage is real, the two tests usually match, and a loss of fibres in one quadrant corresponds to a visual field defect in the same area.
Patients diagnosed with glaucoma generally have two eye examinations a year and a full set of instrumental tests once a year.
Available treatments, from eye drops to surgery
Today there are medical, laser and surgical treatments, and in most cases they keep the disease under control for years. My approach is gradual: start with the least invasive option and step up only if needed.
Eye drops
They are the first step: pressure-lowering drops prescribed by the ophthalmologist. They can have local and general side effects, so it is worth checking that the patient tolerates the chosen molecule well. They are, however, a lifelong therapy, and this is their real limit: they have to be instilled every day, for decades, without forgetting. Not every patient manages to keep up this consistency, and consistency is exactly what the result depends on.
Laser on the trabecular meshwork: SLT and MLT
Selective laser trabeculoplasty (SLT) improves the outflow of fluid from the eye. It is an outpatient treatment lasting a few minutes, well tolerated, which increases the outflow of aqueous humour and lowers the pressure. A more recent variant is micropulse laser trabeculoplasty (MLT), which works on the same target with a different thermal profile.
810 nm micropulse laser
It works on the other side of the problem: instead of increasing outflow, it reduces the production of aqueous humour by acting on the ciliary body. It is covered in more detail further down this page.
Minimally invasive surgery of the trabecular meshwork
The trabecular meshwork is the natural route through which fluid leaves the eye: it works like the knit of a wool jumper, and the tighter or more blocked the stitches, the less fluid can pass. There are micro-stents, a few hundred microns in size, that are inserted exactly there to reopen the passage. They are the entry point of glaucoma surgery, and they are most often considered during cataract surgery in a patient who has both conditions: the operation takes a few minutes longer and uses the micro-incision already made.
Filtering surgery
When the previous options are not enough, the next step is classic filtering surgery, sclerectomy and trabeculectomy. These operations are more effective at lowering the pressure, but require more demanding post-operative management. This is why the order matters: eye drops, laser, minimally invasive surgery, and only then filtering surgery.
Acute glaucoma
Acute glaucoma, unlike chronic simple glaucoma, stays silent most of the time: it occurs in patients who have no eye symptoms and no other evident disease. It is one of the few true eye emergencies, together with retinal detachment and retinal vascular events, and it appears suddenly: after stress, after drops that dilate the pupil, after anaesthesia, in situations where adrenergic tone is particularly high.
What happens inside the eye
The eye predisposed to an acute attack is a small eye, with little space in its front part. When the pupil dilates, the iris crowds the iridocorneal angle and the fluid can no longer drain. The pressure rises quickly: from a normal value of around 16 mmHg it can reach 50 to 60 mmHg. At that point the eye is hard, red and painful, the pupil is mid-dilated and does not react, and nausea, vomiting, headache, intense photophobia and restlessness appear. These are the symptoms that bring the patient to the eye emergency department.
How it is treated, and why it should be treated earlier
Treatment consists of making a small opening in the iris: this is done with the YAG laser (iridotomy) or surgically (iridectomy). The point is that this opening should be made in calm conditions (eye not inflamed, normal pressure, relaxed patient) and not as an emergency. Having to do it in the emergency department means that the anatomical predisposition had not been identified beforehand.
Who is at risk and how they are identified
An acute attack affects people with a particular anatomy: a smaller than average front part of the eye. It happens mainly in long-sighted (hyperopic) people and in those whose lens has swollen because of cataract. A long-sighted patient between sixty and eighty years old with advanced cataract fits the risk profile.
Identifying them requires the slit lamp and a study of the iridocorneal angle. Traditional gonioscopy works, but today I prefer to document the angle with anterior segment tomography: it produces an image that shows the patient the narrowed space and the iris closing the angle, and the decision is made together on that image.
If the angle is at risk, the way forward is laser iridotomy. There is also a more radical solution: removing the natural lens. Once cataract surgery has been performed, the risk of an acute attack drops substantially, because the artificial lens is much thinner than the natural one and gives space back to the angle. This is why, in an at-risk patient who is already due for cataract surgery soon, iridotomy is often not necessary.
Glaucoma treatment with 810 nm micropulse laser
Glaucoma is treated by lowering the pressure in the eye, and there are only two ways to do it: reduce the production of aqueous humour or increase its outflow. Most eye drops and traditional angle lasers work on outflow; surgical procedures, as a rule, also serve to let more fluid out of the eye.
The 810 nanometre micropulse laser works on the other side instead. The wavelength is infrared and the pulse is micropulsed, that is, delivered as a train of short pulses: this makes it possible to act on the ciliary body (the part of the eye that produces aqueous humour), reducing its activity without destroying it, as happened with earlier-generation lasers.
This difference has widened the indications. Previously this type of treatment was reserved for refractory absolute glaucoma, that is, painful eyes with no remaining visual function, with the aim of preserving the eyeball. With micropulsation it is also possible to treat open-angle glaucoma and glaucoma that does not respond well to medical or surgical therapy, without ruling out any later treatment, filtering or medical.
The treatment is repeatable and is performed with the eye closed, so it can be done in the clinic, without the need for a sterile environment. It causes moderate pain that can last up to 24 hours. The ciliary processes are at the basis of the eye’s metabolism and must not be compromised: they are destroyed only in extreme cases, whereas with the micropulse laser their activity is simply reduced, in a repeatable way.
Frequently asked questions about glaucoma
Can glaucoma be cured?
Glaucoma cannot be cured. The damage already done to the optic nerve is irreversible, because lost nerve fibres do not regenerate. What can be done, and is done in most cases, is to lower the pressure in the eye and stop progression, preserving the sight that remains. This is why early diagnosis changes everything: the sooner you act, the more visual field is left to protect.
What are the first symptoms of glaucoma?
In the chronic form, the most common one, there are no early symptoms. The loss starts in the peripheral visual field and the brain compensates for it, so the person notices only when the damage is already extensive. This is what makes it necessary to measure eye pressure from the age of 40 to 50, even with good sight. Acute glaucoma is the exception: red and painful eye, blurred vision, headache, nausea and vomiting. There the symptoms are present, they are intense and they require immediate assessment.
How long does glaucoma take to cause blindness?
There is no timeframe that applies to everyone: it depends on the pressure level, the type of glaucoma, how much damage was already present at diagnosis and how closely treatment is followed. Untreated chronic glaucoma generally takes years, often decades, to seriously compromise sight, and it is precisely this slowness that makes it insidious, because it does not raise the alarm that would prompt a check-up. With timely diagnosis and pressure kept at the right values, most patients keep functional sight throughout their lives.
How is eye pressure lowered?
There are only two routes: reduce the production of aqueous humour or increase its outflow. Eye drops act on either front depending on the molecule. Laser on the trabecular meshwork and trabecular micro-stents work on outflow; the 810 nm micropulse laser reduces production. Filtering surgery creates an alternative exit route. The choice depends on the starting value, the state of the optic nerve and how well the current therapy is holding.
Do glaucoma eye drops have side effects?
They can, both local and general, and they vary greatly from molecule to molecule: redness and burning, changes to the eye surface with prolonged use, and in some classes systemic effects on heart rate and breathing. This is not a reason not to use them, it is a reason to tell your ophthalmologist: there is almost always a better-tolerated alternative, or a preservative-free formulation. What you should not do is stop on your own initiative.
Can eye drops be stopped?
Not on your own: stopping treatment makes the pressure rise again. There are, however, treatments that make it possible to reduce the number of eye drops and, in some patients, to stop them: laser on the trabecular meshwork and micro-stents placed during cataract surgery. It is not a guaranteed outcome and it depends on the starting situation: it is assessed case by case, with the test results in hand.
Are OCT and visual field the same thing?
No, and they are not alternatives: they are used together. OCT measures anatomy, that is, how many nerve fibres there are around the optic nerve head. The visual field measures function, that is, whether those fibres are working. OCT sometimes shows a loss of fibres before the visual field detects it, and that is the information that allows action to be taken earlier. Both must be repeated over time and compared with previous tests, because it is the change between one check-up and the next that tells whether treatment is working.
What is best avoided when you have glaucoma?
The advice I give most often comes down to three points. First: do not skip doses and do not stop treatment on your own, because the pressure rises again quickly and without warning signs. Second: do not use cortisone eye drops on your own initiative or because they worked for a relative, since in some people cortisone raises eye pressure. Third: head-down positions held for a long time and efforts made while holding your breath raise the pressure temporarily. This does not mean giving up physical activity, it means discussing it at your visit and adapting how you exercise.
Is glaucoma hereditary?
Family history is one of the recognised risk factors: people with a parent or sibling with glaucoma are more likely to develop it and have good reason to start check-ups earlier. The other factors I consider are age, a thin cornea, high myopia and some general vascular conditions. The role of chronic stress on eye pressure is also being discussed.
Can glaucoma and cataract be operated on together?
Yes, and it is one of the most frequent situations. In patients with cataract and mild to moderate open-angle glaucoma, trabecular micro-stents can be implanted during the same operation, through the micro-incision already made. The surgery takes a few minutes longer and the patient faces a single operation.
If you would like your case assessed, you can book a visit at the Turin and Ivrea practices with Dr. Alberto Bellone, Reference Physician, Ophthalmology Functional Unit, Casa di Cura Sedes Sapientiae (Humanitas Group), Turin. Please bring your previous tests to the visit, especially visual field and OCT, because it is the comparison over time that provides the information that matters.
