Brief overview
- What is glaucoma? A group of eye diseases that can destroy the retina and optic nerve in advanced stages and lead to blindness if left untreated. Also known as glaucoma.
- Symptoms: Initially hardly any symptoms, in advanced stages visual field loss, eye pain, headaches. In acute glaucoma (glaucoma attack), symptoms such as sudden visual disturbances, very hard eyeball, severe headaches and eye pain, nausea.
- Cause: Irreversible damage to the optic nerve, often (partly) caused by excessive intraocular pressure.
- Co- and risk factors: e.g. older age, low blood pressure, high blood pressure, coronary heart disease (CHD), diabetes mellitus, elevated blood lipids, migraine, tinnitus, severe short- or long-sightedness, family history of glaucoma, dark skin color, smoking.
- Treatment: medication, surgery if necessary.
- Prognosis: If left untreated, glaucoma leads to blindness.
Glaucoma: Description
Glaucoma is one of the most common causes of blindness. In industrialized nations, glaucoma is the third most common cause of blindness. It is estimated that around 14 million people in Europe suffer from glaucoma. In many cases, those affected are unaware of their condition.
As soon as a person with glaucoma notices the visual disturbances themselves, the damage to the retina and/or optic nerve is often already well advanced. And damage that has already occurred can usually no longer be reversed.
Glaucoma is more common with increasing age. After the age of 75, seven to eight percent of people are affected, after the age of 80 even 10 to 15 percent.
Forms of glaucoma
Secondly, depending on the anatomy of the chamber angle, glaucoma can be divided into two main groups: open-angle glaucoma (wide-angle glaucoma) and narrow-angle glaucoma (angle-closure glaucoma).
Open-angle glaucoma
By far the most common form of glaucoma in older people is primary open-angle glaucoma – it is found in around nine out of ten glaucoma patients. This form of glaucoma is caused by a drainage disorder in the so-called trabecular meshwork (spongy tissue in the chamber angle), the cause of which is unknown. Because the aqueous humor cannot drain properly, the intraocular pressure increases. Primary open-angle glaucoma is chronic and affects both eyes.
Secondary open-angle glaucoma is less common. In this case, the aqueous humor cannot drain properly due to a blockage within the trabecular meshwork. This obstruction can be caused by inflammatory cells, red blood cells or tumor cells, for example, or be the result of cortisone therapy.
Narrow-angle glaucoma
Sometimes the cause of narrow-angle glaucoma – i.e. the flattened anterior chamber – remains unknown (primary narrow-angle glaucoma). In contrast, secondary narrow-angle glaucoma can be attributed to another eye disease, for example rubeosis iridis (abnormal vascularization of the iris due to a lack of local blood flow, e.g. in diabetes patients).
If this outflow disorder occurs acutely (as an attack), it is referred to as a glaucoma attack (also known as “acute angle closure”). The chamber angle is suddenly displaced. The intraocular pressure can then increase so much within a few hours that the retina and nerves are immediately and permanently damaged (risk of blindness!).
A glaucoma attack is an ophthalmological emergency that must be treated as quickly as possible!
Other forms of glaucoma
There are several other types of glaucoma.
Congenital glaucoma, on the other hand, is rare: in affected babies, the trabecular meshwork in the corner of the eye is not fully formed for unknown reasons or the outflow of aqueous humor is obstructed by tissue. This form of glaucoma is already noticeable in the first year of life and can lead to blindness relatively quickly.
Glaucoma: symptoms
The symptoms of glaucoma vary depending on the form and stage of the disease.
Chronic glaucoma: symptoms
The vast majority of patients have chronic progressive glaucoma – most commonly primary open-angle glaucoma, sometimes also chronic narrow-angle glaucoma. In such cases, there are usually no symptoms in the early stages. Glaucoma patients often only notice their disease at an advanced stage due to increasing visual field defects (scotomas):
Occasionally, visual field defects also occur in the center of the visual field.
Other symptoms of glaucoma can include redness of the eyes, headaches and eye pain. In addition, prolonged elevated intraocular pressure can lead to swelling (edema) of certain cells in the eye, resulting in light refractions that are perceived as colored rings or halos (auras) around bright light sources.
Acute glaucoma (glaucoma attack): Symptoms
In acute narrow-angle glaucoma (glaucoma attack), the sudden sharp increase in intraocular pressure within a few hours triggers the following symptoms:
- palpable hard eyeball
- Severe eye pain and headaches
- reddening of the eyes
- Colored circles of light (halos) around light sources
- reduced visual acuity
- Fixed, moderately wide pupil (“fixed” means that it hardly constricts at all or not at all when exposed to light)
- Nausea and vomiting
Congenital glaucoma: symptoms
If a baby shows the following symptoms, congenital glaucoma may be the cause:
- Enlargement of the eyeball and cornea (cow’s eye or bull’s eye, medical term: buphthalmos)
- Enlarged corneal diameter
- corneal opacity
- light-sensitive eyes (photophobia)
- watery eyes
If you notice these signs in your child, you should definitely see a pediatrician! They can refer you and your child to a specialist.
Glaucoma: causes and risk factors
As mentioned above, there are primary forms of glaucoma, the cause of which is unknown, and secondary forms of glaucoma, which develop as a result of another disease or an eye injury, for example.
An overview of the most important causes and risk factors for glaucoma:
- Deposits (plaques) that obstruct the trabecular meshwork in the chamber angle and the “Schlemm’s canal” in the chamber angle (open-angle glaucoma). The deposits are usually age-related.
- low blood pressure or a very low second blood pressure value (diastolic blood pressure), e.g. due to heart valve defects or certain disorders of vascular function
- chronic high blood pressure (hypertension), which damages the blood vessel wall
- chronically elevated blood lipid levels (such as hypercholesterolemia), which lead to deposits in the blood vessels (arteriosclerosis)
- diabetes mellitus and other metabolic diseases that alter the inner wall of the blood vessels and impede blood flow
- Autoimmune diseases involving the blood vessels
- Smoking, as nicotine constricts the blood vessels (including those in the eye)
- Circulatory disorder (vascular dysfunction)
- (temporary) spasmodic vasoconstriction such as Raynaud’s syndrome, migraine, tinnitus
- severe inflammation of the eye or in the eye, which can lead to scarring or deposits in the angle of the chamber
- long-term cortisone treatment
- severe myopia or hyperopia beyond four diopters, in which the shape of the eyeball and the anterior chamber of the eye is altered
- Cases of glaucoma in the family
- dark skin color
Increased intraocular pressure
In many cases, glaucoma is associated with increased pressure in the eyeball (intraocular pressure). This occurs when the aqueous humor builds up in the anterior chamber of the eye, for example due to an obstruction in the outflow:
The aqueous humor is produced by special cells and released into the posterior chamber of the eye. From there, it flows into the anterior chamber of the eye, where it is then drained via the drainage system in the angle of the chamber. The constant exchange of aqueous humor is important for the function of the eye. The aqueous humor carries nutrients and oxygen to the lens and the cornea, which have no blood vessels of their own. It also serves as an optical medium.
Intraocular pressure only elevated in every second patient
Recent studies have shown that only around half of glaucoma patients actually have abnormally high intraocular pressure. In the other 50 percent of those affected, the intraocular pressure is within the normal range. Nevertheless, their blood flow is also disturbed as a result of an imbalance between intraocular pressure and perfusion pressure. However, this imbalance is not due to obstacles to the outflow of aqueous humor (as is the case with increased intraocular pressure), but possibly to changes in the blood vessels or disorders of the general circulatory function.
Glaucoma: examinations and diagnosis
The doctor’s visit begins with a detailed doctor-patient consultation (anamnesis). This is followed by various eye examinations.
Medical history
The doctor can use the information from the anamnesis interview to gather your medical history. Possible questions the doctor may ask are, for example
- Do you suffer from vision problems?
- Do you have circulatory problems?
- Do you have any known underlying conditions such as diabetes mellitus, migraines or high blood pressure?
- Have you injured your eye, for example in an accident or during sport?
- Are you taking any medication?
- Do you tolerate the prescribed medication?
- Are you taking the medication as prescribed by your doctor?
- Are there any eye diseases in the family?
Inspection of the eye
The medical history is followed by an inspection of the eye. The doctor looks at the eyelids, the cornea, the lens and the lacrimal apparatus and looks for possible changes. For example, redness or pus may indicate certain diseases.
Slit lamp examination
If glaucoma is suspected, the ophthalmologist assesses in particular the spatial conditions of the anterior chamber of the eye and the depth of the anterior chamber. He also looks for changes in the iris and unusual pigmentation of the cornea.
The slit lamp examination takes place in a darkened room and is completely painless for the patient.
Intraocular pressure measurement (tonometry)
The pressure in the eyeball can be measured quickly using the so-called applanation tonometer. The measuring plate of the device presses on the cornea of the eye from the front (in the area of the pupil) and determines the pressure required to deform a defined area (applanation = flattening, flattening; tonus = tension, pressure). As the cornea of the eye is very sensitive to touch, it is anaesthetized with a local anaesthetic for the examination.
In most people with glaucoma, intraocular pressure values above 21 mmHg are measured, in extreme cases (glaucoma attack) sometimes even more than twice as high.
When taking the measurement, the ophthalmologist will take into account that the pressure in the eye is often higher in older people without glaucoma being immediately present. In addition, the measurement result is also influenced by the thickness of the cornea, which should therefore be determined by a further examination (pachymetry – see below).
Controversial benefits
However, the benefit of intraocular pressure measurement in glaucoma diagnostics is controversial. Intraocular pressure is not elevated in every glaucoma patient. This means that glaucoma may be present even if the measurement results are normal. The benefits and risks of the examination must be weighed up in each individual case and discussed with the ophthalmologist.
Measurement of corneal thickness (pachymetry)
For this purpose, the entire front and back surface of the cornea is imaged with a slit-shaped beam of light and recorded by a high-resolution camera. A computer program uses these images to calculate the thickness at thousands of individual points and ultimately reconstructs a highly accurate thickness profile.
Ophthalmoscopy (funduscopy)
Ophthalmoscopy (funduscopy) is particularly informative for the diagnosis of “glaucoma” because it allows glaucoma damage and the stage of the disease to be visualized directly:
Using an ophthalmoscope – a mixture of magnifying glass and light source – the ophthalmologist assesses the condition of the retina, its blood vessels and the optic nerve head. To enable the doctor to view as large a section of the back of the eye as possible, the patient is given special eye drops to dilate the pupil shortly before the examination.
Examination of the chamber angle (gonioscopy)
Narrow-angle glaucoma is characterized by a shallow chamber angle. In open-angle glaucoma, outflow blockages through the iris and possible age-related plaques can be detected. Adhesions and discoloration can also indicate glaucoma.
Visual field measurement (perimetry)
An important examination for detecting existing retinal or nerve damage is visual field measurement (perimetry). It is carried out for each eye individually (the other eye is covered during the examination).
During the examination, the patient is presented with optical stimuli at different locations in the room one after the other without being allowed to look directly at them. If he perceives a light stimulus, he must indicate this by pressing a button. This makes it possible to determine the size of the visual field and any visual field defects (scotomas), as occur in glaucoma.
Measurement of blood flow
Various examinations can determine the blood flow to the retina and the optic nerve. Frequently used methods are fluorescein angiography (X-ray contrast examination of the blood vessels in the eye), thermography (recording the heat emitted by the eyeball as a measure of blood flow) and capillary microscopy (observation of the finest blood vessels in the retina under magnification).
As the relationship between intraocular pressure and the pressure in the blood vessels of the eye is not correct in glaucoma, a blood pressure measurement is also part of the routine examinations.
Glaucoma: Treatment
In the case of secondary glaucoma, the underlying cause (e.g. another eye disease or a disease affecting the whole body such as diabetes) must also be treated if possible.
Lowering the intraocular pressure
The aim of glaucoma treatment is to permanently reduce an elevated intraocular pressure below a critical level so that enough blood can flow to the cells of the retina and the optic nerve again. This “critical intraocular pressure” varies from person to person. It depends on the average pressure at which the blood circulates in the blood vessels of the eyeball (perfusion pressure):
Lowering the intraocular pressure to below the individual target value can often be achieved with medication, but sometimes glaucoma surgery is also necessary. This depends on the cause and the course of the disease.
Glaucoma: medication
Not all forms of glaucoma can be treated satisfactorily with medication. However, in the most common form of glaucoma, primary open-angle glaucoma, treatment with medication is often sufficient.
Patients are usually given special eye drops that need to be applied once or several times a day. The drops contain active ingredients that are intended to reduce the intraocular pressure below the individual target value – by reducing the production of aqueous humor and/or improving the outflow of aqueous humor:
- Carbonic anhydrase inhibitors (e.g. dorzolamide, brinzolamide, acetazolamide): These also reduce the formation of aqueous humor. They are normally used as eye drops. However, in the event of an acute attack of glaucoma, they can also be injected directly into a vein so that they take effect more quickly.
- Sympathomimetics/alpha-agonists (e.g. apraclonidine, brimonidine): They can both reduce the production of aqueous humor and increase its outflow.
- Prostaglandins (e.g. latanoprost, bimatoprost, travoprost, tafluprost): They ensure that the aqueous humor can drain better. As a side effect, the color of the iris may become darker.
- Parasympathomimetics (e.g. pilocarpine, carbachol): They constrict the pupil (miosis), thereby widening the aqueous humor angle and facilitating the outflow of aqueous humor. Unpleasant side effect: The narrowing of the pupil restricts the vision of older people in particular.
Which medication is ultimately prescribed and in what dosage depends primarily on the form of glaucoma to be treated. In any case, it is important that the doctor and glaucoma patient work well together and that the patient adheres to the therapy consistently.
Glaucoma: surgical interventions
If medication to treat glaucoma cannot sufficiently and reliably reduce the intraocular pressure, surgery is required. Medication and surgical glaucoma therapies are sometimes combined.
In the case of an attack of glaucoma, for example, medication is first used to relieve the pressure acutely and only then is the eye operated on. In contrast, glaucoma surgery is performed as early as possible in the early childhood form of glaucoma (primary congenital glaucoma).
The following procedures are available for the surgical treatment of glaucoma:
Trabeculotomy/trabeculotomy
The operation is performed under local anesthesia and can often be performed on an outpatient basis. The procedure takes around 30 minutes.
Iridectomy and laser iridotomy
The iris is opened through a small incision – either with a fine knife or a laser. Through the small hole, the aqueous humor can pass directly from the posterior to the anterior chamber of the eye, where it then drains through a channel.
This procedure is useful if the patient has narrow-angle glaucoma and there is a risk of angle closure (glaucoma attack). It is performed under local anesthesia.
Laser trabeculoplasty
The sponge-like tissue in the chamber angle (trabecular meshwork) is bombarded with laser beams, which improves the outflow of aqueous humor. This method is mainly used for patients with open-angle glaucoma. Ideally, the pressure in the eye can be lowered by around eight millimetres of mercury (mmHg).
Cyclophotocoagulation/cyclocryocoagulation
The surgical procedure focuses on the ciliary body – a ring-shaped part of the middle part of the eye to which the lens is “attached” and which is involved in the production of aqueous humor.
During the procedure, the ciliary body is destroyed with a laser (cyclophotocoagulation) or cold pen (cyclocryocoagulation) in the area that forms the aqueous humor – the amount of aqueous humor produced decreases, which lowers the intraocular pressure.
Both procedures for the treatment of glaucoma can be considered for secondary glaucoma and for glaucoma where other operations have been unsuccessful.
Opening of the Schlemm’s canal
Schlemm’s canal plays a major role in the drainage of aqueous humor. During the procedure, the surgeon locates the canal with a probe and then creates an opening from there to the anterior chamber of the eye. This improves the drainage of the aqueous humor.
Regular check-ups
Regular check-ups with an ophthalmologist are also an important part of glaucoma treatment. It makes sense to have one to three check-ups per year – depending on how far the glaucoma has progressed.
Glaucoma: disease progression and prognosis
Without treatment, glaucoma leads to blindness because it continues to damage the visual cells of the retina and the optic nerve. The progression of the disease accelerates the longer the glaucoma has been present. Once damage has occurred, it can no longer be reversed.
This makes it all the more important to detect glaucoma at an early stage, avoid risk factors and consistently continue any treatment that has been started. The good news is that glaucoma can usually be stopped and vision preserved with suitable medication and/or surgery.
