Glaucoma

Glaucoma is a disease characterized by progressive damage to the optic nerve fibers, which, if left untreated, can lead to irreversible vision loss or even blindness. In its early stages, it is often asymptomatic, but there are also forms that present with sudden and severe symptoms. Several types are known, commonly characterized by elevated intraocular pressure, although normal-tension glaucoma is also recognized. Early detection and an appropriate treatment strategy are essential to preserve vision. The goal of therapies is to halt or at least slow the damage to the optic nerve, thereby preserving the patient’s vision as well and for as long as possible.

What is glaucoma?

Glaucoma is a disease characterized by progressive damage to the optic nerve fibers, which, if left untreated, leads to irreversible vision loss or even blindness. In glaucoma, intraocular pressure is most often elevated. In a healthy eye, the fluid inside the eye, the aqueous humor, is continuously produced and drained from the anterior segment of the eye. This fluid has a dual role: on the one hand, it nourishes the anterior tissues of the eye, such as the cornea and the lens, and on the other hand, it maintains the appropriate intraocular pressure, which is vital for the healthy functioning of the eye.

However, when the delicate balance between aqueous humor production and drainage is disrupted, the internal pressure of the eye increases, which significantly accelerates the optic nerve damage characteristic of the disease. Very prolonged elevated intraocular pressure can later lead to irreversible vision loss. It is also worth knowing that elevated intraocular pressure alone does not constitute glaucoma.

It is important to note, however, that glaucoma does not develop solely as a result of increased intraocular pressure. In addition to intraocular pressure, other factors also play a role in the development of the disease. One such factor is the autoregulatory dysfunction of the optic nerve circulation, when the vessels supplying the optic nerve are unable to effectively adapt to fluctuations in blood pressure and ocular blood supply. As a result, inadequate blood supply can also contribute to ischemic (caused by lack of blood) damage to the optic nerve head.

This is particularly true in the case of normal-tension glaucoma, when the internal pressure of the eye is not high, yet progressive optic nerve damage still develops. In addition, oxidative stress, genetic causes, inflammatory and immune-mediated processes, and weaker biomechanical properties of certain parts of the optic nerve head are also held responsible for the development of the disease.

What are the types of glaucoma and their symptoms?

The symptoms of glaucoma largely depend on which type of the disease we are discussing. Glaucoma can be classified into four main groups, within which several subtypes can be distinguished. Distinguishing between the different types is particularly important from a treatment perspective, as there are forms where certain treatments are ineffective or even contraindicated.

Open-angle glaucoma

Primary open-angle glaucoma (POAG) is the most common type, in which the anterior chamber angle appears open, but tiny obstructions occur in the aqueous humor drainage system, gradually increasing intraocular pressure. Its exact cause is unknown, but several risk factors have been associated with it (see below).

For most people, the disease has no symptoms or early warning signs, which is why ophthalmic screening plays a particularly important role. This type of glaucoma develops slowly and often does not cause noticeable vision loss for years. However, if open-angle glaucoma is not diagnosed and treated in time, it can cause gradual and permanent vision loss. It generally responds well to medical treatment, especially if recognized and treated early.

Normal-tension glaucoma (NTG) refers to the form of the disease when the clinical picture is similar to the above, but the intraocular pressure is within the normal range. Examination of the circulatory system is particularly important in such cases, as the nerve fibers of the optic nerve head are adversely affected by reduced blood flow caused by low blood pressure.

It is important to mention here an ophthalmic condition that is closely related to the disease. We speak of ocular hypertension (OHT) when, with an open angle, we measure higher intraocular pressure, but we cannot detect any other signs of glaucoma by any method. It usually requires monitoring, but in high-risk patients, treatment may also be prescribed. One-fifth of ocular hypertension cases eventually convert to primary open-angle glaucoma.

Angle-closure glaucoma (ACG)

In angle-closure glaucoma, the abnormal tissue position of the anterior segment of the eye causes the increase in intraocular pressure. The forward bulging of the iris partially or completely closes the anterior chamber angle, which prevents fluid from draining from the eye, and thus the intraocular pressure suddenly increases, as it continues to be produced continuously.

In acute angle-closure glaucoma (AACG), symptoms develop suddenly and cause pronounced complaints. Blurred vision and seeing rainbow-colored halos around light sources may be the initial symptom, followed by rapid vision loss and the appearance of intense eye pain, a feeling of pressure that may extend to the area around the eye. This condition is called an acute glaucoma attack and usually affects only one eye (although it is present in both, just to varying degrees). At this time, the eye is inflamed, angry red in color, and the pupil is also wider than on the opposite side. General symptoms such as headache, abdominal pain, vomiting, and lethargy are often associated. Occasionally, an acute glaucoma attack may resolve slowly on its own, but this almost always leaves permanent damage.

An acute glaucoma attack requires immediate, emergency care.

The long-standing untreated form is called chronic angle-closure glaucoma (CACG). In this case, the obstruction is usually not complete and thus does not cause pronounced complaints, but severe, permanent damage develops in the eye to the optic nerve, iris, and anterior chamber angle.

A special condition must be mentioned here. Plateau iris refers to an anatomical condition in which the tissues involved in the production and drainage of aqueous humor are in an abnormal position relative to each other. In this case, the deeper-lying part of the iris closes the anterior chamber angle, although upon simple examination it appears flat and open. The condition eventually leads to chronic angle-closure glaucoma. Establishing the diagnosis often requires additional specialized examinations (anterior segment OCT, UBM ultrasound examination) in addition to gonioscopy.

Secondary glaucoma

In these forms, the increased intraocular pressure is not only due to an imbalance in aqueous humor production and drainage, but some other well-identifiable triggering cause also plays a role (e.g., injury, inflammation, medication). Several subtypes are known.

• Pseudoexfoliative glaucoma (PXG): In this form, flaky material accumulates and detaches from the outer layer of the lens. Environmental and genetic causes (LOXL1 gene mutation) are considered to be the underlying factors. This material collects in the space formed by the iris and cornea, in the anterior chamber angle, and can block the aqueous humor drainage system, resulting in increased intraocular pressure.
• Neovascular glaucoma: In this type, new but abnormal vessels form (neovascularization, new vessel formation) on the iris and in the anterior chamber angle, which directly and indirectly inhibit the drainage of aqueous humor and cause increased intraocular pressure. This type is characterized by always occurring in association with some other disease (most commonly diabetes or severe circulatory disorder affecting the eye).
• Pigment glaucoma (PG): In this case, due to the abnormal position of the iris, its posterior part rubs against the suspensory fibers of the lens, and small tissue fragments are shed from it. These pigment granules enter the aqueous humor and gradually accumulate in the drainage channel, through which they cannot pass due to their size, thus leading to increased intraocular pressure.
• Traumatic glaucoma: This type develops as a result of blunt trauma to the eye (ball, blow) or penetrating injury (accidents). Intraocular pressure may appear immediately after the trauma or even years later. It presents a varied picture and their treatment is often complex.
• Uveitic glaucoma: In cases of intraocular inflammation, inflammatory elements can lead to increased intraocular pressure. Special forms include Fuchs heterochromic uveitis, Posner-Schlossman syndrome, and glaucoma associated with herpetic uveitis.
• Steroid-induced glaucoma: Steroid use in certain individuals can lead to elevated intraocular pressure, which, if prolonged, can damage the optic nerve head. Symptoms usually appear after at least 3 weeks of medication use, but may occasionally occur earlier.

Congenital and juvenile glaucoma

Congenital glaucoma is a genetic disease occurring in newborns and infants.

Juvenile glaucoma is a special subform of the open-angle form affecting individuals between 3 and 35 years of age.

Risk factors and prevalence of glaucoma

The development of open-angle glaucoma is influenced by numerous factors.

• Age: Glaucoma is somewhat more common in the age group over 40, and the prevalence rate increases significantly over 60-70 years of age.
• Genetic predisposition: In the case of family history (especially parent, sibling), the chance of developing the disease is much higher
• Ethnic factors: It is more risky for certain ethnic groups, such as people of African or Caribbean descent.
• Ophthalmic diseases: Certain eye injuries, eye inflammations, ophthalmic diseases, and ophthalmic surgeries may increase the risk of glaucoma.
• Ophthalmic abnormalities: Higher intraocular pressure, thinner corneal thickness, and moderate or high myopia represent an increased risk.
• Systemic diseases: Diabetes, high blood pressure, or other vascular diseases (especially if accompanied by low diastolic blood pressure) may contribute to the development of the condition.

What tests do we perform to diagnose glaucoma?

Early detection of glaucoma is critically important to prevent vision loss. The following examinations are important in establishing the diagnosis:

• Slit-lamp examination: A comprehensive examination of the eye is fundamentally necessary for diagnosis.
• Tonometry: This refers to the measurement of intraocular pressure and is essential in glaucoma, as only this can determine higher intraocular pressure. Its normal value is considered to be between 10–21 mmHg, but this may vary from individual to individual (25 is not necessarily pathological, and 18 may also indicate disease).
• Pachymetry: This refers to the measurement of corneal thickness. If its value deviates from the average (550 µm), it provides distorted information about intraocular pressure. With a thin cornea, the true internal pressure of the eye is higher, while with a thicker cornea, it is lower than measured.
• Gonioscopy (anterior chamber angle examination): Gonioscopy allows examination of the anterior chamber angle and the drainage system called the trabecular meshwork located there. Through a special mirrored contact lens, the doctor assesses whether the anterior chamber angle is open or closed, and looks for various abnormalities such as pigment, blood or other deposits, new vessel formation, scarring adhesions, injuries, or abnormal anatomical position. Anterior chamber angle examination is necessary to determine the subtype of glaucoma and also affects the treatment strategy.
• Visual field examination (perimetry): The purpose of visual field examination is to assess the peripheral parts of vision. Its modern form is automated perimetry, which maps the visual field in detail according to a predetermined program and shows if there are less sensitive areas or visual field defects in it. It is an indispensable examination in the early diagnosis and monitoring of glaucoma.
• Optical coherence tomography (OCT): With this non-invasive imaging method, high-resolution cross-sectional images can be made of the retina and optic nerve structures. With optic disc OCT examination, the thickness of the nerve fiber layer can be measured in different parts of the optic nerve head, which is essential for the early detection of subtle damage caused by glaucoma.

The above examinations are crucial in early diagnosis, developing treatment strategies, monitoring the disease, and assessing the effectiveness of treatment.

To establish the diagnosis, form an opinion on the effectiveness of treatment, and assess the rate of disease progression, several examinations performed at defined intervals are required; intraocular pressure within the normal range alone does not guarantee that the treatment is appropriate at that point.

What treatment options are available for glaucoma?

When treating glaucoma, the goal is to preserve the visual field and vision for as long as possible, which is achieved by reducing intraocular pressure and preventing further damage to the optic nerve. The following treatment methods are available:

Conservative treatments

Eye drop treatments*

One effective method of reducing intraocular pressure is treatment with eye drops. The medications achieve their effect in three different ways:

• They increase drainage through the anterior chamber angle (cholinergic parasympathomimetics, rho-kinase inhibitors)
• They stimulate fluid drainage through the posterior drainage system of the eye (uveoscleral) (prostaglandin analogs, alpha-receptor agonists)
• They reduce aqueous humor production inside the eye (beta-receptor blockers, alpha-receptor agonists, carbonic anhydrase inhibitors)

Drops belonging to different pharmacological groups can be combined with each other, thereby increasing their intraocular pressure-lowering effect. However, using multiple preparations from the same group or using one preparation more frequently than prescribed does not increase effectiveness.

Generally, one drop should be instilled 1-2 times into the middle part of the lower conjunctival sac, and the eye should be kept closed for at least 1 minute afterward. When using multiple types of drops, at least 5 minutes must elapse between their applications.

Systemic treatments

There are cases when eye drops are not sufficient to reduce intraocular pressure and surgery cannot be performed. In such cases, intraocular pressure can be rapidly reduced with various medications orally or intravenously. They are generally used in hospital settings.

Laser treatments

Laser Trabeculoplasty*

Selective laser trabeculoplasty (SLT)* is a modern laser procedure primarily used to treat open-angle glaucoma. SLT uses low-energy laser during treatment of the trabecular meshwork, thereby minimizing tissue damage. The goal of the treatment is to increase aqueous humor drainage. The procedure is painless, can be performed quickly, can be repeated several times, and has few side effects.

SLT is particularly beneficial for patients who do not tolerate eye drops or for whom medical treatment is not sufficient to reduce intraocular pressure. The effectiveness of the procedure generally results in a 20-30% reduction in intraocular pressure, and the desired pressure level can be maintained long-term in a significant proportion of patients.

SLT has traditionally been used as an adjunctive treatment, but in recent years, increasing research and clinical experience support that it can also be effective as a primary therapy. According to the results of the LiGHT (Laser in Glaucoma and Ocular Hypertension) study, SLT used as a first-line treatment is as effective as eye drop therapy, while reducing patients’ medication dependence and improving quality of life.

Argon laser trabeculoplasty (ALT) is a similar but older procedure, which is now rarely used, as SLT involves less tissue damage and is more effective in the long term.

Micropulse laser trabeculoplasty (MLT)* attempts to achieve intraocular pressure reduction without tissue damage. It is a relatively new procedure; currently, little data is available on long-term effectiveness. The treatment is completely painless and can be repeated as needed.

Peripheral laser iridotomy (LPI)*

Peripheral laser iridotomy provides effective and rapid treatment in all forms of angle-closure glaucoma. Iridotomy can prevent an acute glaucoma attack or, if it has already developed, can be rapidly treated with it.

During the procedure, a small opening is created with a laser in the upper part of the iris, through which the aqueous humor produced further back can freely flow forward toward the anterior chamber angle. Thanks to this artificial opening, the drainage obstruction characteristic of the condition is resolved, aqueous humor flow improves, and thus the iris is released from the anterior chamber angle.

In rare cases, if laser treatment is not feasible, a small section of the iris must be surgically excised (iridectomy).

Before iridotomy, anesthetic and pupil-constricting drops are instilled on the eye surface, and then a special contact lens is placed for the duration of the treatment. The treatment is safe, painless, and lasts only a few minutes. After the procedure, the eye should not be rubbed for a few hours, but there are no other lifestyle restrictions.

Argon laser peripheral iridoplasty (ALPI)*

During the procedure, using an argon laser, small, superficial burn injuries are caused at the peripheral parts of the iris, which results in localized contraction of the tissues. The procedure is mainly used in a special glaucoma case (plateau iris), but it may also need to be applied in angle-closure glaucoma when the iris is excessively wedged into the anterior chamber angle.

Before treatment, anesthetic and pupil-constricting drops are applied, and then the treatment lasting a few minutes is performed through a special contact lens.

Cyclophotocoagulation (CPC)

CPC is a destructive laser procedure in which the ciliary body responsible for aqueous humor production is treated to lower intraocular pressure. It is used in almost any type of severe, advanced glaucoma when other treatments are no longer sufficient or feasible.

Surgical interventions

Surgical treatments for glaucoma previously typically came to the forefront if medical and laser treatments were no longer effective. Nowadays, however, these procedures are playing an increasingly important role even in the early stages of treatment, especially with the spread of minimally invasive techniques.

The goal of surgical interventions is to improve drainage capacity at the natural drainage site of aqueous humor (anterior chamber angle, trabecular meshwork, Schlemm’s canal) or to create new, artificial pathways, in order to keep intraocular pressure stably low.

Traditional surgeries

The classic surgical procedures for glaucoma treatment are generally major surgeries requiring hospitalization.

Trabeculectomy

Trabeculectomy is a traditional surgical procedure used to treat glaucoma, in which a new channel is created for the drainage of aqueous humor, thereby reducing the internal pressure of the eye. During the surgery, a small opening is made in the sclera (white part of the eye) toward the anterior chamber angle, so that fluid from the eye can easily flow under the conjunctiva, where it is absorbed. It is very effective but involves a longer recovery time and risk of complications.

Shunt implants

Shunt implants used in glaucoma are small devices with a tubular component that, when implanted in the anterior part of the eye, provide an artificial channel for the drainage of aqueous humor. The larger part of the implant is sutured under the conjunctiva, where this small tube (shunt) drains the aqueous humor, where it is absorbed. This helps keep intraocular pressure stably low, which is particularly important in severe or treatment-resistant glaucoma. The procedure is effective but may involve a longer recovery time and complications.

Minimally invasive glaucoma surgery (MIGS)

To reduce the complications of traditional surgeries, several procedures have been developed that are safe, require a smaller incision, and are as effective as traditional surgeries. The procedures can be classified into two main groups, depending on whether some device is also implanted into the eye or not. We will mention a few important procedures in each group, without claiming completeness.

MIGS without implant

Minimally invasive glaucoma surgeries attempt to achieve increased fluid drainage or reduced production through some procedure.

Femtosecond laser trabeculotomy (FLIGHT) is a novel procedure in which the opening of the inner part of the trabecular meshwork is performed with a femtosecond laser in open-angle glaucoma.

Canaloplasty is another relatively new procedure in which Schlemm’s canal is dilated, thereby improving fluid drainage. It is less invasive than trabeculectomy and is also mainly used in open-angle glaucoma.

Cyclocryotherapy is a freezing technique with which the tissue responsible for fluid production is destroyed, thereby reducing intraocular pressure. It is a treatment reserved for severe, therapy-resistant glaucoma cases.

MIGS with implant placement

This subgroup of MIGS includes those procedures in which a small implant is inserted into the anterior chamber angle with a brief intervention, thereby ensuring better fluid outflow from the eye. Several implant types are known, each solving this task slightly differently.

+ Cataract surgery*

Although not specifically an anti-glaucoma surgery, it is known that cataract surgery also has a place in the surgical treatment of glaucoma. By removing the lens and implanting an intraocular lens, the anterior part of the eye becomes less crowded, any spatial disproportion improves, and thus intraocular pressure decreases. It is used in open- or angle-closure glaucoma and certain secondary glaucoma types, as an adjunctive treatment or independently, in certain cases as the primary treatment of choice. Compared to previous surgeries, the complication rate is lower.

For glaucoma treatment, cataract surgery can also be performed in combination with MIGS treatments, thereby increasing the effectiveness of treatment if this is predictably necessary.

*treatments available at our center

What preventive options are available against glaucoma?

The development of glaucoma cannot be prevented, but in certain types, early detection and treatment can significantly reduce the extent of vision impairment.

In the case of angle-closure glaucoma, an acute glaucoma attack can be prevented by timely laser iridotomy.

Regular ophthalmic screening examinations are particularly important after age 40 and for those at higher risk. Early diagnosis and appropriate treatment can help prevent optic nerve damage and vision loss.

A healthy lifestyle can reduce the frequency of open-angle glaucoma development. Fruits and vegetables rich in antioxidants, as well as leafy greens, may have a protective effect. Non-strenuous physical exercise has an intraocular pressure-lowering effect, so its regular practice is recommended.