Glaucoma

Glaucoma is a series of eye diseases that lead to damage to the nerve cells of the retina and the optic nerve in the later stages of the disease. Glaucoma is usually caused by increased intraocular pressure in the chambers of the eye. The two chambers of the eye are located in the front part of the eye near the lens and are connected by the pupil. The chambers are filled with aqueous humor, which is normally renewed by a balanced inflow and outflow. The angle of the ventricle is the area where the aqueous humor flows in and out.

If glaucoma is left untreated, over time it can lead to visual field loss and even complete blindness. By the time the affected person notices the disturbance of his vision, the optic nerve is often already severely and irreversibly damaged.

Glaucoma is one of the most common causes of blindness. In industrialized countries, about one in three cases of blindness is due to glaucoma. According to estimates, approximately three million people in Germany, for example, have elevated intraocular pressure (the main cause of glaucoma). About 800,000 of them have already developed glaucoma. Most of those affected are unaware of their condition.

The risk of developing glaucoma increases with age. About eight percent of people over 75 and up to 15 percent of people over 80 suffer from glaucoma.

Different forms of glaucoma are distinguished. These can be divided into four main groups:

• Primary open-angle glaucoma:This form ofglaucomais the result of a disturbance in the outflow of aqueous humor due to deposits (called plaque material). It is the most common type of glaucoma in older people. Normal-tension glaucoma is a chronic form of open-angle glaucoma in which the eye pressure is within the normal range.
• Angle-closure glaucoma: If the chamber angle is closed, an angle-closure glaucoma can occur. A distinction is made between acute and intermittent angle-closure glaucoma. In contrast to earlier definitions, the term glaucoma is now only used for chronic angle-closure glaucoma (in which damage to the optic nerve occurs).
• Primary congenital glaucoma:This is caused by developmental abnormalities of the angle of the ventricle, resulting in a congenital outflow obstruction of the aqueous humor.
• Secondary (acquired) glaucoma:This form of glaucoma is caused by other eye diseases that cause aqueous humor outflow obstruction. Examples of this would be complications from injuries, eye inflammation or diabetes mellitus.

Glaucoma is the result of damage to the optic nerve. This damage can be due to many causes, but the most common is increased intraocular pressure.

Increased intraocular pressure

The anterior and posterior chambers of the eye are filled with aqueous humor, which supplies the cornea and the lens of the eye with nutrients, since they do not have their own blood vessels. This aqueous humor is produced by the ciliary body (used to suspend the lens in the posterior chamber of the eye). From the posterior chamber, the aqueous humor flows through the iris to the anterior chamber, on through the angle of the chamber into the canal of Schlemm, and from there on into the bloodstream. If the outflow of the aqueous humor is blocked, it backs up, which increases the intraocular pressure and subsequently damages the optic nerve. Normally, intraocular pressure is in the range of 10 to 21 mmHg.

Circulatory disorders

However, there are also forms of glaucoma that are not due to increased eye pressure. In these cases, it is assumed that the retina is damaged by a disturbed blood supply to the eye, thus causing the typical symptoms of glaucoma.

Secondary glaucoma

Secondary glaucoma is always triggered by other underlying diseases. Diabetic retinopathy (i.e. retinal damage as a result of diabetes mellitus) and occlusion of the central retinal vein are by far the most common causes.

Another trigger can be a long-term therapy with cortisol. Although this does not necessarily lead to glaucoma, some people react very sensitively to cortisol therapy. In these people, intraocular pressure increases (which can cause glaucoma) shortly after starting therapy.

Risk factors for developing glaucoma are:

• older age (glaucoma usually occurs after the age of 40)
• glaucoma in the family - especially in first-degree relatives
• low diastolic blood pressure (second blood pressure value)
• Presence of cardiovascular diseases such as CHD (coronary heart disease), artherosclerosis or pAVK (peripheral arterial occlusive disease)
• hypertension (high blood pressure)
• Hypercholesterolemia (elevated cholesterol levels in the blood)
• nearsightedness or farsightedness in the range of more than four dioptres
• severe eye inflammation
• smoking
• long-term cortisol treatment
• circulatory disorders (Raynaud's syndrome, tinnitus, migraine)
• diabetes mellitus (diabetes)
• people with dark skin have an increased risk of glaucoma

The symptoms of glaucoma vary depending on which form of glaucoma is present:

The most common form of glaucoma is primary open-angle glaucoma. This usually goes unnoticed for a long time before the first visual disturbances occur. The first symptom is that the affected person notices halos or rings around light sources. If no treatment of the glaucoma is initiated, the optic nerve is progressively damaged, which can lead to visual field loss or even complete blindness.

In the course of an acute glaucoma attack in narrow-angle glaucoma, the following symptoms occur:

• severe headache as well as eye pain
• nausea and vomiting
• sudden deterioration of vision
• reddening and hardening of the eyeball
• sometimes appearance of a bright glow around light sources (halo)

In most cases, only one eye is affected by the symptoms. The acute glaucoma attack may last from a few hours to several days and may recur at varying intervals.

Primary congenital glaucoma manifests in young children mostly within the first two years of life. In particular, noticeably large, "attractive" eyes, increased lacrimation, photophobia, eyelid spasms, and eye rubbing may be indicative of congenital glaucoma.

The symptoms of secondary g laucoma are identical to those of primary open-angle glaucoma. In this form, the disease also goes unnoticed for a long time.

A glaucoma is diagnosed by means of various apparative examinations:

Tonometry (intraocular pressure measurement).

With the help of tonometry, the intraocular pressure of the eye can be determined. Normally, this lies between 10 and 21 mmHg, but in the case of glaucoma, elevated values are often found. However, the age of the patient and the presence of concomitant diseases must be taken into account, as the average intraocular pressure increases with age. In addition, it is recommended to measure the corneal thickness, as this has a strong influence on the intraocular pressure. However, if the intraocular pressure is normal, glaucoma cannot be ruled out with certainty, as it may also be due to other causes.

Gonioscopy (examination of the chamber angle)

In the course of a gonioscopy the chamber angle can be examined. The gonioscope is placed directly on the cornea - with the help of a special lens, the chamber angle can be viewed (as this cannot normally be viewed from the outside due to its position). Among other things, the width of the chamber angle, possible adhesions, outflow blockages and discolorations are determined. These factors may be indicative of glaucoma.

Perimetry (visual field measurement)

To complement the diagnosis, the ophthalmologist performs a visual field measurement. Optical stimuli are shown at different positions in the visual field - in this way the outer and inner limits of the visual field as well as the strength of perception are determined. Since visual field defects in glaucoma only occur as soon as more than 30 percent of the optic nerve is damaged, this examination can only detect advanced disease.

Ophthalmoscopy (examination of the back of the eye)

Ophthalmoscopy can determine whether there is already damage to the optic nerve (optic nerve). The fundus of the eye, which lies at the back of the eyeball, is examined through the dilated pupil with the aid of an ophthalmoscope.

Slit lamp examination

This involves examining the eye in a darkened room using a microscope and a slit light beam. The width of the chamber angle and the depth of the anterior chambers of the eye are used to diagnose glaucoma. In addition, changes in the iris (iris skin) or atypical pigmentation of the cornea are also detected.

Regular check-ups

Since glaucoma cannot be reversed, regular check-ups with an ophthalmologist are of particular importance for early diagnosis and treatment.

Since damage to the optic nerve cannot be reversed, the treatment of glaucoma is limited to preventing the progression of the disease. With the help of medications, eye drops, laser treatments and surgical measures, a progression of the nerve damage can usually be prevented or at least delayed. The most important measure is to diagnose glaucoma as early as possible through regular examinations by the ophthalmologist and in this way prevent the loss of vision. Existing therapy may need to be adjusted over time, as glaucoma can progress unnoticed despite treatment.

The forms of therapy vary depending on the type of glaucoma:

• Chronic open-angle glaucoma: in this case, an attempt is made to reduce the elevated intraocular pressure to the normal range by means of drug therapy.
• Acute glaucoma attack:This is an emergency which, if left untreated, can lead to complete blindness within a short time. To remedy the acute attack, an attempt is first made to lower the intraocular pressure with the aid of medication. Subsequently, a surgical intervention (iridotomy, iridectomy) is attempted to correct the outflow disturbance of the aqueous humor in the area of the chamber angle.
• Congenital glaucoma: In this form of glaucoma, eye surgery is performed as early as possible.

The following medications are used to treat glaucoma:

• Beta blockers: these are commonly used in the treatment of glaucoma. Their effect is to reduce the production of aqueous humor. If other underlying diseases such as bronchial asthma or AV block (impaired conduction of the heart) are present, beta blockers must not be used.
• Carboanhydrase inhibitors:These drugs reduce the production of aqueous humor and thus lower the ventricular pressure. In the treatment of an acute glaucoma attack, carbonic anhydrase inhibitors are sometimes administered intravenously. Some agents (dorzolamide, brinzolamide) can also be administered as eye drops.
• Prostaglandins: Prostaglandins facilitate the drainage of aqueous humor, which can lower intraocular pressure. A possible side effect is that treatment may darken the color of the iris (iris) somewhat.
• Alpha-sympathomimetics: These decrease the production of aqueous humor.
• Parasympathomimetics/Miotics:These drugs cause a constriction of the pupil, which at the same time widens the chamber angle and facilitates the outflow of the aqueous humor. Particularly in the elderly, vision deteriorates due to the constricted pupil.

Depending on the type and extent of the glaucoma, the drugs are used individually or in combination. In most cases, glaucoma can be treated well with medication, so that surgery is not necessary. However, the prerequisite for this is that the therapy is carried out consistently, otherwise the irreversible damage to the optic nerve will progress.

If a sufficient improvement of the glaucoma cannot be achieved by medication, various surgical methods are still available:

• Laser trabeculoplasty:this procedure is primarily performed on patients with open-angle glaucoma. The sieve-like plexus (trabecular meshwork) located in the chamber angle is bombarded with a laser beam so that the outflow of the aqueous humor is improved. In this way, pressure reductions of up to 8mmHg (millimetres of mercury) can be achieved. Laser treatment is performed on an outpatient basis under local anesthesia (local anesthetic). However, the effect of the treatment often wears off after some time.
• Trabeculectomy/Trabeculotomy: In this procedure, an artificial drain is placed between the anterior chamber and the outer conjunctiva to allow the aqueous humor to drain away. The aqueous humor is then drained through the blood vessels of the conjunctiva. The surgical procedure takes about 30 minutes and is performed under local anesthesia.
• Iridectomy/iridotomy with laser: This procedure is performed in cases of narrow-angle glaucoma if there is a risk of complete angle closure. A tiny hole is cut in the iris (iris skin) with the help of a laser beam, through which the aqueous humor can flow directly from the posterior chamber of the eye into the anterior chamber. The iridotomy is performed under local anesthesia.
• Cyclophotocoagulation/cyclocryocoagulation:The principle of cyclophotocoagulation is that the aqueous humor producing part of the ciliary body is cooked so that less aqueous humor is formed and thus the eye pressure is reduced. Cyclophotocoagulation is based on a similar principle, except that in this method the ciliary body is destroyed with the help of a cold pen. These two treatment approaches are usually only performed in secondary glaucoma and in therapy-resistant forms of glaucoma (in which no satisfactory improvement could be achieved by other operations).
• Opening of Schlemm's canal:In the congenital form of glaucoma, an opening of Schlemm's canal is surgically created in the area of the chamber angle.

For a good prognosis, it is crucial to detect and treat glaucoma as early as possible. Without treatment, the disease progresses progressively to complete blindness. Since the damage to the optic nerve cannot be reversed, regular check-ups with an ophthalmologist are the most important strategy to prevent eye damage due to glaucoma.

In most cases, the deterioration of vision caused by glaucoma can be prevented with the help of medication or surgery. In most cases, treatment with eye pressure lowering medication is sufficient, so that further measures are not necessary.

Since glaucoma is a hereditary disease, relatives of glaucoma patients may want to have their intraocular pressure checked regularly by an ophthalmologist before the age of 40.