What is it?

Glaucoma is a progressive and degenerative optic neuropathy (disease of the optic nerve) that occurs, in most patients, by an elevation of intraocular pressure above the tolerance level of the patient.
Normal levels of intraocular pressure range from 14 to 18 mm Hg.
Glaucoma has been identified as one of the main causes of irreversible blindness in Western countries, in patients over 60 years of age. However, a diagnosis in the initial stages of the disease can delay its progression, until it is practically undetectable for the patient, which significantly reduces the risk of blindness.

It is very important to bear in mind that glaucoma remains a practically asymptomatic disease until late stages, so patients are not aware of their problem until they have lost a lot of vision (which cannot be recovered). That is why going to your ophthalmologist regularly is the best preventive strategy for this disease.

Causes

The eye is continuously producing a transparent liquid, called aqueous humor, whose function is to nourish the ocular structures of the anterior segment of the eye. Under normal circumstances, the amount of aqueous humor produced is drained through the iridocorneal angle. This mechanism keeps the pressure inside the eye (intraocular pressure) within a stable range. When the iridocorneal angle does not work properly, aqueous humor accumulates in the anterior chamber, which causes an increase in intraocular pressure and consequent damage to the optic nerve.

Types of Glaucoma

All forms of glaucoma can be classified into primary and secondary according to: The iridocorneal angle (the area of union between the iris and the cornea), the morphology of the head of the optic nerve, visual field defects and various risk factors (pressure intraocular, age, cardiovascular problems).

Primary glaucomas:

·         Congenital primary forms:

o   Congenital glaucoma: It appears from birth to the second year of life.

o   Primary childhood glaucoma: It appears between the 3rd and 10th year of life.

o   Glaucoma associated with congenital anomalies (aniridia, rubella, etc.).

·         Primary open-angle glaucoma:

o   Primary juvenile glaucoma suspect.

o   Primary juvenile glaucoma.

o   High pressure primary open-angle glaucoma suspect.

o   High pressure primary open-angle glaucoma.

o   Normal pressure primary open-angle glaucoma suspect.

o   Normal pressure primary open-angle glaucoma.

o   Ocular hypertension: (intraocular pressure is above “normal” values, but there is no visible damage to the optic nerve).

·         Angle closure glaucoma:

o   Acute glaucoma.

o   Chronic angle-closure glaucoma.

Secondary glaucomas:

·         Secondary open-angle glaucomas:

o   Pseudoexfoliative glaucoma: Caused by an accumulation of material from the lens (pseudoexfoliation).

o   Pigmentary glaucoma: Caused by an excess of pigment in the iridocorneal angle.

o   Traumatic glaucoma.

o   Lens-induced open-angle glaucoma.

o   Glaucoma associated with intraocular hemorrhage.

o   Uveitic glaucoma.

o   Glaucoma due to intraocular tumors.

o   Iatrogenic secondary open-angle glaucoma: Due to corticosteroid treatment, or due to ocular surgery and/or laser.

o   Glaucoma induced by increased episcleral venous pressure.

·         Secondary angle-closure glaucomas:

o   Secondary angle-closure glaucoma with pupillary block.

o   Neovascular glaucoma.

o   Aqueous misdirection (malignant or ciliary block) glaucoma.

o   Iris and ciliary body cysts.

o   Glaucoma associated with retinopathy of prematurity.

o   Congenital anomalies.

Who can suffer glaucoma?

Glaucoma can affect people of all ages, from newborns (congenital glaucoma) to the elderly.

When we talk about primary open-angle glaucoma (the most prevalent form), there are a number of factors associated with an increased risk of glaucoma. These factors can be modifiable or non-modifiable

Non-modifiable risk factors:

·         Age: More prevalent in people over 40 years of age.

·         Sex: higher prevalence in women (debatable).

·         Race: Higher prevalence in people of African, Hispanic, or Asian descent.

·         Family history of glaucoma.

·         Corneal thickness. Thin corneas are associated with an increased risk of glaucoma.

·         High refractive defects (myopia or hyperopia).

·         Previous eye trauma.

Modifiable risk factors:

·         High intraocular pressure.

·         Poorly controlled diabetes.

·         Systemic hypertension.

·         Systemic circulatory disorders (Rainaud’s phenomenon), migraine, heart disease.

Symptoms

In early stages, primary open-angle glaucoma does not present specific symptoms. The same occurs with patients with normal-tension glaucoma (intraocular pressure is within normal values, but still causes damage to the optic nerve) or patients with ocular hypertension (high intraocular pressure, but no damage to the optic nerve), or patients with “suspected” glaucoma (Glaucoma cannot be confirmed, but there are indications of its presence).

Performing regular eye exams is the best strategy to prevent irreversible damage caused by glaucoma.

In the advanced stages, the patient may already be aware of the visual field loss.

Diagnosis

A standard ophthalmological examination, which includes study of visual acuity and refraction, intraocular pressure, study of the iridocorneal angle, analysis of corneal thickness, study of the fundus, and study of the visual field is sufficient to diagnose most cases.

The specific tests used for diagnosing glaucoma are:

·         Tonometry or study of intraocular pressure: Normal intraocular pressure is a “statistical term”, which refers to a range of intraocular pressure within the normal adult population. The mean intraocular pressure is 15 mm Hg, although values between 12 and18 mm Hg are considered normal. Intraocular pressure can be measured by:

o   Contact methods: Goldmann and / or Perkins applanation tonometer.

o   Non-contact methods: Air tonometer, pneumotonometry, corneal hysteresis analysis, etc.

·         Gonioscopy: Study of the iridocorneal angle. Its purpose is to determine the structure of the iridocorneal angle, by identifying its anatomical structures. It is considered a fundamental test in glaucoma, since it allows to differentiate open-angle glaucomas from closed-angle glaucomas. Gonioscopy can be performed directly through a lens or through ultrasonic biomicroscopy.

·         Analysis of the optic nerve head / retinal nerve fiber layer: Glaucoma is a disease of the optic nerve (optic neuropathy), so to study the optic nerve head is crucial. The goal is to assess the structural damage caused by glaucoma. There are different methods:

o   Study with lens in the slit lamp. It is the first approximation and is very useful in moderate / advanced cases, but for very incipient cases it is not definitive.

o   Photographs of the fundus: They allow to document and compare, objectively, between two evolutionary moments of the disease. They can be two-dimensional or three-dimensional.

o   Imaging methods: Their great advantage consists in the possibility of objectively analyzing the progression of the disease through different evolutionary moments.

§  Optical coherence tomography (OCT): Provides a quantitative analysis of both the head of the optic nerve and the thickness of the retinal nerve fiber layer (the fibers that make up the optic nerve).

§  Heildelberg Retinal Tomograph (HRT): Provides a quantitative analysis of the optic nerve head and the retinal nerve fiber layer.

§  Polarimetry or Automatic Fiber Analyzer (GDX): Allows quantitative analysis of the nerve fiber layer of the retina.

·         Perimetry: It is currently done with automatic perimeters. The visual field study is mandatory in patients with glaucoma, both for diagnosis and for follow-up. Perimetry measures the functional damage caused by glaucoma. The test to be carried out (study of the 10º, 24º, or 30º) or the strategy (standard or rapid) will depend on the particularities of each case. In some highly selected cases, it may be necessary to perform manual perimetry with the Goldmann perimeter.

Glaucoma Stages

In order to standardize the language used by specialists, it is very important to establish a classification of glaucoma. The visual field is often used to classify the stage of glaucoma. From a perimetric (functional) point of view, glaucoma can be classified as: Incipient, moderate, or advanced, depending on the visual field damage. The classification of the patient with glaucoma will determine the follow-up and the treatment strategy.

Treatment

Glaucoma causes irreversible (permanent) damage to the optic nerve and the visual field. However, the damage caused by glaucoma can be stopped, making diagnosis of the disease in its early stages is extremely important. There are different therapeutic strategies: medical treatment, laser treatment, and surgical treatment. The choice of one or the other depends, fundamentally, on the level of damage (glaucoma stage) and the characteristics of the patient (For example, in a pregnant woman, the only viable option may be surgery). The main goal of treatment (all) is to reduce intraocular pressure.

·         Medical treatment:

o   Medical treatment, in most cases will be topical (eye drops), although for more advanced and difficult cases, it could be necessary to use a systemic treatment (pills). Patient adherence to treatment is essential to achieve optimal results.

o   Some drugs decrease intraocular pressure by reducing aqueous humor production, while other drugs reduce intraocular pressure by increasing aqueous humor drainage. Medical treatment can present a number of local adverse effects, such as, for example, foreign body sensation, itching, stinging, discoloration of the iris eye (prostaglandins), or growth of eyelashes (prostaglandins). In addition, it can have systemic side effects, such as decreased heart rate (beta-blockers) or breathing problems (beta-blockers), mainly in asthmatic patients.

·         Laser treatment:

o   It is a pre-surgical treatment. It can be the first option mainly in elderly patients with pseudoexfoliative and / or pigmentary glaucoma. It is outpatient and is generally performed in consultation or in a special room.

·         Surgical treatment:

o   There are several types of surgical treatments:

§  Minimally invasive surgery.

§  Trabeculectomy.

§  Drainage devices.

Why to perform minimally invasive glaucoma surgery?

Although trabeculectomy, due to its effectiveness (in terms of reducing intraocular pressure), is still the most commonly used surgical technique for the treatment of glaucoma, the possibility of serious complications that compromise the patient’s vision has motivated the search for techniques that, without sacrificing their effectiveness, are safer.

Minimally invasive procedures for glaucoma surgery have been developed in an attempt to find effective alternatives, but with a better safety profile, than traditional filtering surgery (trabeculectomy).

Minimally invasive procedures have not been developed to replace traditional surgery (trabeculectomy and / or valve implants) in all patients, but for those cases whose characteristics do not require excessively low intraocular pressure, but which benefit from its better safety profile.
Due to the reduction in the incidence of serious complications, minimally invasive procedures have allowed the ophthalmologist to recommend or perform anti-glaucomatous surgeries in patients who otherwise would not have had surgery.
The patient’s access to surgery in the earlier stages of the disease has reduced the number of antiglaucoma drugs that the patient receives throughout his life.

There are currently available different minimally invasive procedures, their selection depends on both the characteristics of the patient and the preferences of the surgeon.
Roughly, minimally invasive procedures can be classified into:

·         Procedures that enhance the eye’s own drainage system.

·         Procedures that divert the aqueous humor to the subconjunctival space (below the conjunctiva).

·         Procedures that divert the aqueous humor to the suprachoroidal space (enhance aqueous humor flow through the uveoscleral pathway).

·         Procedures that reduce the production of aqueous humor by ablation (elimination) of the ciliary body (area of the eye where aqueous humor is produced).

In addition to their better safety profile, minimally invasive procedures have meant a reduction in surgery times. These procedures are performed through small incisions, which facilitates the postoperative period of the patient.
Minimally invasive procedures can be performed alone (glaucoma surgery) or in combination with cataract removal (glaucoma and cataract surgery at the same time), which is a clear advantage for the patient.

Finally, although these surgical procedures are very safe, they are not without complications, mostly mild, although they require postoperative ophthalmological control.

Your ophthalmologist will recommend the surgical technique that best suits your needs.

Prognosis

The earlier the diagnosis (in more incipient stages), the better the prognosis. Performing regular reviews and good compliance with treatment are crucial factors to achieve optimal results, reducing the progression of the disease.