Glaucoma – Optic nerve degeneration
Glaucoma is a degeneration of the optic nerve, the cable made up of millions of nerve fibers that transmits images from the eye to the brain. It most often occurs in cases of ocular hypertension, caused by an accumulation of fluid (aqueous humor) in the eye. The increased intraocular pressure damages the optic nerve and causes it to lose fibers at an accelerated rate. Glaucoma is often asymptomatic for a long time, meaning that the patient experiences no symptoms before reaching the terminal stage. It is one of the leading causes of blindness in people over 60. However, blindness can often be prevented through early detection and treatment of intraocular pressure, which slows the degeneration of the optic nerve and thus the progression of glaucoma.
What is glaucoma?
Your eye constantly produces aqueous humor, a clear fluid. As aqueous humor is secreted by your eye, the same amount must drain out.
The fluid drains through an area called the iridocorneal angle or trabecular meshwork. This process helps to maintain a stable pressure inside the eye (called intraocular pressure or IOP).
If the trabecular meshwork malfunctions, fluid accumulates. This increases the pressure inside the eye, putting pressure on the optic nerve and damaging it.
Accumulation of aqueous humor
The optic nerve is made up of more than a million tiny nerve fibers. It is like an electrical cable composed of many wires.
As these nerve fibers die, suffocated by eye pressure, blind spots (scotomas) appear in your vision.
You may not notice these blind spots until most of the optic nerve fibers have died.
If all the fibers give way, you will unfortunately become blind.
Forms of glaucoma
There are two main types of glaucoma depending on the mechanisms of intraocular pressure increase.
Primary open-angle glaucoma
This is the most common type of glaucoma. It develops gradually, when the eye does not drain fluid as well as it should (like a blocked drain).
As a result, intraocular pressure increases and damages the optic nerve.
This type of glaucoma is painless and does not cause any changes in vision at first.
Some people may have optic nerves that are sensitive to normal eye pressure.
This means that their risk of developing glaucoma is higher than normal.
It is important to have regular eye exams to detect early signs of optic nerve damage, even without eye pressure.
Rare forms of open-angle glaucoma
Open-angle glaucoma can sometimes be caused by factors other than an excess of aqueous humor. These are called secondary glaucomas, which are often more aggressive:
Pigmentary glaucoma or pigment dispersion – The iris (colored part around the pupil) rubs against the lens (the lens that allows focusing), causing a release of pigment that blocks the trabecular meshwork.
Normal pressure glaucoma – Even though intraocular pressure is normal, the optic nerve is deteriorating too rapidly. This is actually a hypersensitivity of the optic nerve to intraocular pressure.
Pseudoexfoliative glaucoma or pseudoexfoliation – Genetic abnormalities of collagen lead to fragility and alteration of the trabecular meshwork.
Uveitic glaucoma – Eye inflammations are responsible for pressure spikes.
Congenital glaucoma – The trabecular meshwork is malformed during ocular development, resulting in glaucoma from birth.
Juvenile glaucoma – The trabecular meshwork does not develop properly during growth, leading to ocular hypertension and glaucoma from adolescence onwards.
This type of glaucoma occurs when a person's iris is very close to the trabecular meshwork in the eye's drainage angle. The iris can eventually block the drainage angle.
You can imagine it as being like a sheet of paper slipping on the drain of a sink, preventing it from draining.
Angle-closure glaucoma also develops slowly in many people. This is then referred to as chronic angle-closure glaucoma.
Patients have no symptoms or only rare headaches upon waking.
They do not know they are affected until the damage is severe or they suffer an acute attack.
When the drainage angle is suddenly and completely blocked, the intraocular pressure increases very rapidly.
This is what is called an acute angle-closure crisis or acute glaucoma.
This is a genuine eye emergency, and you must consult your ophthalmologist immediately.
Intense eye pain.
A sudden drop in vision.
A diffuse redness.
The sight of rainbows or halos (kaleidoscope)
Severe headaches
Nausea and vomiting associated with headaches.
Symptoms of glaucoma
In the case of open-angle glaucoma, there are no warning signs or obvious symptoms in the early stages. As the disease progresses, scotomas (dark spots) appear in your peripheral (side) vision.
Most people with open-angle glaucoma don't notice any changes in their vision until the damage is severe and irreversible. This is why glaucoma is called the "silent thief of sight."
Regular eye exams can help your ophthalmologist detect this disease before you lose your sight completely. Your ophthalmologist can tell you how often you should be examined.
People at risk of angle-closure glaucoma usually do not experience any symptoms before an attack.
The first symptoms of an attack may be blurred vision, halos (kaleidoscope), mild headaches, or nighttime or morning eye pain.
People with these symptoms should be examined by their ophthalmologist as soon as possible.
People with "normal pressure glaucoma" have eye pressure that is within the normal range (11 to 21 mmHg), but show signs of glaucoma, such as scotomas in their field of vision and optic nerve damage.
However, they are completely asymptomatic in the early stages. Their discovery is often late.
Pigment dispersion syndrome occurs when the back of the iris (pigmented portion around the pupil) rubs against the lens.
This pigment can interfere with the eye's pressure regulation system (trabecular meshwork), increasing eye pressure and leading to pigmentary glaucoma.
Pigmentary glaucoma is often asymptomatic.
Some people with pigment dispersion syndrome or pigmentary glaucoma may see halos or have transient blurred vision and headaches after activities such as jogging or sexual intercourse.
Some people show no signs of glaucoma but have higher than normal eye pressure (called ocular hypertension). These patients are considered "suspected glaucoma" and have a higher risk of developing glaucoma later in life.
Some people are considered suspected of having glaucoma even if their eye pressure is normal. For example, their ophthalmologist may notice something atypical about their optic nerve: too large, too hollow, or too irregular.
Most people suspected of having glaucoma experience no symptoms. That's why you should be closely monitored by your ophthalmologist if you suspect you have glaucoma. The ophthalmologist can check for any gradual loss of optic nerve fibers and, if so, initiate treatment.
What are the risk factors for glaucoma?
Some people have a higher than normal risk of developing glaucoma. These include patients who:
They have high eye pressure.
They are over 40 years old.
Have family members with glaucoma.
They are of African, Hispanic or Asian origin.
They are either very farsighted or nearsighted.
They suffered eye trauma.
They use corticosteroids long-term.
They have a thin cornea (< 500 µm)
Have a thinned or irregular (notched) optic nerve.
They suffer from diabetes, migraines, high blood pressure, poor blood circulation or sleep apnea.
Glaucoma diagnosis
The only reliable way to diagnose glaucoma is through a complete eye exam. A glaucoma screening that only checks eye pressure is insufficient to detect glaucoma.
During a glaucoma examination, your ophthalmologist will:
Measure your eye pressure.
Measure the thickness of your cornea.
Inspect the drainage angle of your eye.
Examine the optic nerve to see if it appears damaged.
He will add, if necessary:
An optical coherence tomography (OCT) scan – The machine scans your optic nerve, counts the optic nerve fibers, and compares their number to a database within the machine. If you have fewer fibers than patients of the same sex and age, you most likely have glaucoma.
A visual field test – The examination is often done during a dedicated appointment slot with an orthoptist. The device tests your light sensitivity in your field of vision in order to diagnose or monitor the progression of scotomas (dark spots).
Treatments and surgery
Glaucoma treatment focuses on managing intraocular pressure. The goal is to achieve the lowest and smoothest possible intraocular pressure so that the optic nerve stops deteriorating.
Treatments involve eye drops, laser therapy, and surgery.
Can glaucoma be cured?
No! The damage caused by glaucoma is permanent and irreversible. Any area of vision lost is lost forever. Fortunately, medication and surgery can prevent the damage from worsening.
Medications – Hypotensive drops
Glaucoma is usually controlled by eye drops that lower eye pressure.
Used every day, at fixed times, these eye drops lower eye pressure.
To lower the pressure, some drops reduce the amount of aqueous humor produced by the eye (like closing the tap). Others reduce the pressure by helping the fluid flow more easily through the drainage angle (like unblocking the siphon).
The product classes used are:
Beta blockers
Prostaglandin analogues
Carbonic anhydrase inhibitors
Alpha mimetics and miotics
Side effects of anti-glaucoma eye drops
Glaucoma medications can help you preserve your vision, but they can also produce side effects. Some eye drops can cause:
Pruritus – A tingling or itching sensation
Hyperemia – Red eyes or red skin around the eyes
Bradycardia – Changes in your pulse and heart rate
Discomfort – a drop in your energy level
Dyspnea – difficulty breathing, especially if you suffer from asthma or COPD.
Dry mouth and eyes
Blurred vision
Eyelash growth
Changes in eye color (iris), skin around the eyes, or the appearance of the eyelids.
All medications can have side effects. Some side effects can be worsened when taken with other medications. It is important to give your doctor a list of all the medications you take regularly.
Never change or stop taking your glaucoma medication without talking to your ophthalmologist.
If you run out of medication, ask your ophthalmologist to renew your prescription.
Laser treatment
There are two main types of laser treatment for glaucoma. They help the aqueous humor drain through the trabecular meshwork. These procedures are usually performed in the ophthalmologist's office.
Trabeculoplasty – This procedure is for people with open-angle glaucoma and can be used instead of, or in addition to, eye drops. The ophthalmologist uses a laser to reshape the trabecular meshwork and improve the drainage angle. This allows fluid to flow more easily and reduces intraocular pressure.
Iridotomy – This procedure is for people with narrow-angle or closed-angle glaucoma. The ophthalmologist uses a laser to create a tiny hole in the iris. This hole facilitates the drainage of fluid to the angle of the eye.
Surgery in the operating room
Some glaucoma surgeries are performed in an operating room. They create a new drainage channel to allow the aqueous humor to leave the eye.
Trabeculectomy – Your ophthalmologist creates a tiny flap in the sclera. They also create a bubble (like a valve) in the conjunctiva, called a filtering bleb. It is usually hidden under the upper eyelid and is not visible. Aqueous humor can drain from the eye through the valve into the bleb. Inside the bleb, the fluid is absorbed by the tissues surrounding the eye, lowering the pressure in the eye WITHOUT any drainage.
Sclerectomy – This is a variant of trabeculectomy used to treat narrow-angle glaucoma. It is performed in Latin American and former Soviet countries but is less common in the rest of the world. Trabeculectomy and sclerectomy are both referred to as filtering surgeries.
Glaucoma drainage devices – The ophthalmologist may implant a tiny drainage tube in your eye. The glaucoma drainage implant directs fluid to a collection area (called a reservoir). Your ophthalmologist creates this reservoir under the conjunctiva. The fluid is then absorbed by nearby blood vessels.
Cataract surgery – In some people with narrow angles, removing the eye's natural focusing lens (crystalline lens) can lower eye pressure. With narrow angles, the iris and cornea are too close together. This can cover (block) the eye's drainage channel. Removing the crystalline lens during cataract surgery creates more space for fluid to drain from the eye, thus lowering eye pressure.
Diode laser – In cases of refractory glaucoma, a laser designed to reduce the production of aqueous humor can be used. Unfortunately, its effectiveness is sometimes inconsistent, with excessive drops in pressure or, conversely, increases in pressure.
MIGS – short for minimally invasive surgery. These are new devices designed to lower intraocular pressure or facilitate surgical procedures. The most common technique is the placement of stents (iStent®, Glaukos) in the trabecular meshwork. There are also mini-drains that mimic a trabeculectomy (XenGel and PreserFlo). The use of some of these products must be approached with caution because they are expensive and rarely revolutionary.
Your role in the treatment of glaucoma
Glaucoma treatment requires close collaboration between you and your ophthalmologist.
The treatment should be followed regularly, at fixed times, without ever stopping it.
The follow-up schedule is dictated by the ophthalmologist, approximately every 3-6 or 12 months depending on the severity of the condition, the eye pressure and the worsening of the visual field.
Intraocular pressure is a screening indicator for glaucoma, but by no means a sufficiently reliable monitoring tool. Therefore, visual field testing and OCT scans are absolutely essential in addition to vision and pressure monitoring.
Visual field testing is a tedious and time-consuming examination. It is advisable to schedule an appointment for this test BEFORE your follow-up consultation.
If you have any questions about your eyes or your treatment, talk to your ophthalmologist.
Frequently Asked Questions
Is glaucoma curable?
No! Glaucoma is a progressive degeneration of the optic nerve, and no treatment can regenerate it. The only protective factor is regulating intraocular pressure to stabilize or slow the progression of glaucoma.
Can one live a long time with glaucoma?
Yes, absolutely! Once stabilized, glaucoma has little or no impact on daily life.
Are there any medications that are contraindicated in cases of glaucoma?
Yes and no! It depends on the type of glaucoma and its stability.
In cases of open-angle glaucoma, prolonged use of corticosteroids is best avoided. If it is necessary, close ophthalmological monitoring is required.
In cases of angle-closure glaucoma (or narrow-angle glaucoma), sympathomimetic and anticholinergic medications (including antidepressants) are contraindicated until peripheral iridotomy has been performed. Once the laser procedure is completed, the contraindication to these medications can be lifted.
Are there any contraindications in the case of glaucoma?
No! A normal life and regular monitoring are essential in cases of glaucoma. In the absence of severe visual impairment, no work, sport, medication, or activity is contraindicated.