Green cataract (glaucoma) is a disease of the eye that causes the intraocular pressure to rise above the normal range. The intraocular pressure is normally 10 to 21 mmHg and is maintained mainly by the so-called aqueous humor. This fluid is produced in the interior of the eye, circulates there and is finally led back into the bloodstream via a network of veins between the iris and the cornea. If there is a disturbance of the outflow or an increased production of the aqueous humor, the intraocular pressure increases.
Acute glaucoma: an emergency
Depending on how quickly the pressure inside the eye increases, a distinction is made between acute and chronic glaucoma.
Acute glaucoma, also known as glaucoma, is an ophthalmological emergency in which intraocular pressure can reach levels in excess of 60 mmHg within a short time. This can cause pressure damage to the optic nerve, which can lead to permanent blindness. The episode of glaucoma is usually associated with severe symptoms such as eye and headache and vision deterioration and is usually recognized quickly because of its typical symptom and findings constellation.
In chronic glaucoma, which develops slowly over a long period of time, the symptoms are rather nonspecific and rarely alarming. This is dangerous because chronic glaucoma often remains undetected for a long time, but can damage the optic nerve in the same way as the acute form. For this reason, ophthalmologists from the age of 40 recommend ophthalmological check-ups to be performed in order to detect and treat increased intraocular pressure early.
The diagnosis of glaucoma is made by an ophthalmologist who measures intraocular pressure and changes inside the eye using various instruments. In addition to the direct measurement of the intraocular pressure (tonometry), the visual acuity and the field of vision are determined, the cornea, the anterior and posterior chamber of the eye are assessed, and the optic nerve and fundus are scrutinized. The synopsis of findings and complaints usually leads quickly to the correct diagnosis.
Remove the pressure
The treatment of the green star is regularly carried out with medication. You can choose from a wide range of preparations that either reduce the production of aqueous humor or lead to an improved drainage of the eye water and thus reduce the intraocular pressure. The drugs are administered as drops individually or in combination. Only in severe cases, such as the glaucoma case, the drugs are given through the vein.
While the onset of therapy for chronic glaucoma depends on intraocular pressure, discomfort, and risk factors, acute glaucoma is always treated promptly. In most cases, the drug therapy leads to a sufficient reduction in intraocular pressure. If this is not successful, a whole range of surgical measures are available as an alternative or supplementary treatment option as a further treatment option. They also aim to either improve the aqueous humor drainage or reduce the production of aqueous humor.
Inside the eye, there is a certain pressure, which ensures the optimal functioning of the vision. This so-called intraocular pressure is normally between 10 and 20 mmHg and is maintained and regulated by different systems.
The way of the aqueous humor
The most important element is the aqueous humor. It is produced by the ciliary body in the posterior chamber of the eye, which is located behind the iris and pupil. In addition to the maintenance of intraocular pressure, it is also responsible for the nutrition of the lens, iris and cornea. From the posterior chamber, the aqueous humor flows through the pupil into the anterior chamber and from there into the chamber angle, which contains a venous network (episcleral venous network), which receives the aqueous humor into the blood system. This completes the cycle.
If there is an outflow disorder or an overproduction of aqueous humor, the intraocular pressure increases. The consequence is not always a general deterioration of visual performance, but may also be a pressure-related circulatory disorder of the optic nerve, which leads to irreversible damage.
The green star is still the second most common cause of blindness in adulthood today.About one fifth of blind people suffered from glaucoma. Currently, about 800,000 people in Germany suffer from glaucoma, in about 10% of them is an acute blindness.
Causes and forms
The green star (glaucoma) can arise in different ways and does not always run in the same way. The general term of glaucoma must therefore be subdivided further depending on the form. This classification is useful not only for the development, but also for the treatment of the disease.
The most important forms of glaucoma are:
- Open-angle glaucoma
- Angular block glaucoma and congenital glaucoma
- Normal tension glaucoma
- Secondary forms of glaucoma: pseudoexfoliation glaucoma, pigmentary glaucoma
1. open angle glaucoma
In open-angle glaucomas, there is a reduced outflow of aqueous humor into the episcleral venous network, without the chamber angle being narrowed or even occluded. The outflow of the aqueous humor is "too slow", so that gradually accumulation of aqueous humor in the anterior and posterior chamber of the eye and thus an increase in intraocular pressure comes.
The cause of the reduced runoff is not yet completely explainable. However, certain risk factors associated with the development of open-angle glaucoma are considered certain. These include:
- Age over 40 years
- First-degree relatives who suffer from open-angle glaucoma
- Disease of one eye leads after some time often to the disease of the hitherto still healthy eye.
2. Angular block glaucoma
Angular glaucoma leads to a narrowing of the angle of the iris through the iris, which in the case of a flat anterior chamber approaches or even engages the cornea from behind. Unlike open-angle glaucoma, angle-closure glaucoma usually develops suddenly and is often equated with the term "glaucoma case" - an emergency in ophthalmology.
Higher risk for the farsighted
A risk factor for the development of an angle-closure glaucoma is the farsightedness, since here the eyeball is a little shorter and thus the anterior chamber of the eye is smaller. The disease cataract can also be involved in the development of an angle-closure glaucoma after a long time. The reason for this is the enlarged lens, which obstructs the outflow of aqueous humor into the anterior chamber of the eye, so that the water accumulates behind the iris and pushes it forwards towards the cornea.
Extensions of the pupil can also lead to acute angle-closure glaucoma. The reason is that the pupillary dilation retracts the iris towards the angle of the chamber, where it can narrow the angle of the chamber. Pupil dilatation occurs spontaneously in, for example, darkness, fright or anxiety, but also through certain medications (such as antidepressants) or through the use of drugs such as marijuana, cocaine and speed.
Special form congenital glaucoma
Congenital glaucoma is a special form of angular glaucoma that occurs at or shortly after birth. Cause of congenital glaucoma is an incompletely formed chamber angle or persistent embryonic tissue, which prevents the inflow of aqueous humor to the episcleral venous network. The result is an increased pressure in the eye, which leads to an increase in the corneal diameter and concomitantly to a reduction in vision.
3. Normal pressure glaucoma
Normal glaucoma, as the name implies, causes glaucoma-like symptoms without increasing intraocular pressure beyond normal levels. The causes for the development of normal pressure glaucoma have not been conclusively clarified. On the one hand, an eye pressure that is individually too high for the affected eye is presumed, on the other hand a reduced stability of the optic nerve, which already damages at small pressure increases.
Often women are affected with migraine
Women are more frequently affected than men, and normal-pressure glaucoma also appears to have a weak association with migraine and primary vascular dysregulation (malfunction of the vessels).
The therapy of normal pressure glaucoma corresponds to the normal glaucoma therapy, but with one difference: the intraocular pressures have to be adjusted very individually and carefully, which often proves to be difficult and involves a long course of therapy.
4. Secondary forms of glaucoma
While primary forms of glaucoma, such as open-angle and angled-block glaucoma, have no tangible cause, secondary glaucoma develops in association with certain diseases. These include not only direct damage to the eye, which can lead to glaucoma, but also general diseases, which may also occur in the eye.
Eye full of fibers: the pseudoexfoliation glaucoma
Pseudoexfoliation glaucoma is the most common form of secondary glaucoma. It is caused by a hereditary disorder of the connective tissue, which leads to an increased formation of elastic fibers in the eye. These very fine, fibril-like fibers deposit on the lens and the chamber angle as a whitish-flaky material and thus lead to a drainage obstruction of the aqueous humor and a constantly rising intraocular pressure.
Often meets young men: pigmentary glaucoma
Pigmentary glaucoma, also called pigment dispersion glaucoma, also belongs to the group of secondary glaucomas. This type of glaucoma is caused by small pigment granules that can be removed from the iris and move the angle of the chamber.The result is a disturbed discharge of the aqueous humor into the episcleral venous network of the chamber angle. Pigmentary glaucoma mostly affects younger men, in whom myopia is known. The treatment is not always easy.
Green Star: basics and causes
Not all types of glaucoma lead to the same symptoms. On the contrary: While some occur suddenly, the others appear creeping and are often recognized late. For this reason, it makes sense to differentiate much more between acute and chronic glaucoma in symptom search and diagnosis as well as in later treatment planning than to clarify the exact cause and to classify glaucoma by its cause.
Severe pain in acute glaucoma
Acute glaucoma, also known as glaucoma, occurs within a very short time and is typically accompanied by severe eye and head pain. The pain in the area of the eye can spread to the forehead and upper jaw and in some cases even radiate into the chin. Typically, it also causes vegetative symptoms such as severe nausea, vomiting and cold sweat. Furthermore, eyesight can be reduced and eyes reddened and tears.
As the symptoms are overall very rapid, scary and lead to significant functional limitations in everyday life, usually a doctor is visited quickly. This is also very important, as the rapid increase in intraocular pressure to 60 mmHg can lead to reduced perfusion of the optic nerve, which ultimately leads to the death of the nerve and can lead to blindness.
Above all, acute angle-closure glaucoma goes hand in hand with a rapidly progressing course.
Less noticeable: chronic glaucoma
Slow forms of glaucoma, such as open-angle glaucoma, but also congenital glaucoma, are much less symptomatic compared to acute forms of glaucoma. Often there are only unspecific complaints such as:
- a headache
- Redness of the eye
Since the symptoms are far less stressful, the symptoms are often assigned to the right disease late. In some cases, it may already have come to limitations of vision and the visual field. Visual field defects arise from the outside, resulting in a so-called blinker eye. Occasionally there is also a limitation of central vision.
Although chronic glaucoma progresses slowly and causes nerve damage only at a relatively late stage, the timely start of a treatment is still very important because the disease can take the same untreated exit as the glaucoma case - in the worst case, blindness.
Warning sign in babies
Newborns and infants suffering from congenital glaucoma are restless, often crying with no obvious cause and are difficult to calm down. Congenital glaucoma continues to show that affected children are prone to increased tears, have red eyes, and keep bringing their hands to their eyes. The cornea may be clouded and the corneal diameter increased.
Parents who notice these symptoms in their child should consult a doctor for further clarification and treatment.
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Questions and answers about the symptoms
Since every form of glaucoma must be treated, a targeted diagnosis by the attending ophthalmologist is an important prerequisite for all further therapeutic steps. For this purpose, there are various instruments that are used in routine and in emergency diagnostics and provide good evidence of the disease stage.
Provision is the best protection
While the case of glaucoma represents an ophthalmological emergency, which can generally only be prevented with precautionary measures, chronic glaucoma often only becomes noticeable when damage to the optic nerve has already occurred. Therefore, ophthalmologists recommend an annual eye check-up from the age of 40. With known glaucoma in the family, a pre-existing diabetes mellitus and a severe inflammation or injury to the eye even from the age of 35 years.
In a screening for diseases of the eye, the following investigations are usually carried out:
- vision test
- Visual field determination (perimetry)
- Measurement of intraocular pressure (tonometry)
- Reflection of the fundus (funduscopy)
- Slit lamp examination (gonioscopy)
1. eye test
The vision test examines the visual acuity in the distance and near. For this purpose, the ophthalmologist usually uses certain charts, on which, for example, symbols, letters or numbers are shown in different sizes, which must be recognized from a well-defined distance. Depending on the size at which you can still recognize the requested symbols, it can be deduced how good your eyesight is. A value of 1.0 means a vision of 100%. Values below indicate a worse, values above a better vision according to age.
Vision is therefore tested because both short-sightedness and hyperopia are risk factors for the development of glaucoma. Glaucoma itself does not reduce vision until late stages.
Perimetry determines how tall your visual field is.The visual field is the area of vision that can be perceived when the eye is fixed to a point without moving the eyes or the head.
Your cooperation is required
In an ophthalmological examination, the eyes are separated and measured computer-controlled. You usually sit on a stool and look at a fixed point in the middle of a hemisphere in front of you. One after the other lights up different points of light, which you should recognize or perceive without taking your eyes off the center of the picture. Every light perception must be confirmed by pressing a button. The computer calculates from all values in the wake, how big your field of vision is and which points you may not have registered.
In glaucoma, the visual field is usually changed first at the lateral edges. Later, then also missing light points in the middle of the picture. These constellations can already provide the first clear indications of the presence of glaucoma.
Disadvantage of perimetry is that you have to concentrate very well to comply with all instructions at the same time. If this is not successful, the measurement may be erroneous and in some cases no valid results.
Tonometry, also known as intraocular pressure measurement, provides direct evidence of increased ocular pressure and can be tested with various measurement methods.
Pressure on the cornea
Probably the most commonly used form of intraocular pressure measurement is applanation tonometry. A kind of pen is placed on the cornea and then pressed gently by a few millimeters. Based on the resulting pressure resistance can be measured, how high the intraocular pressure is.
The disadvantage of this method is that it depends on how thick the cornea is. It measures on average a thickness of 0.55 mm. For a thinner cornea, the measured values are incorrectly too low, too high for a thicker cornea. These deviations have to be corrected by computation, which makes applanation tonometry prone to error.
Regardless of corneal thickness, intraocular pressure can be measured by modern Pascal tonometry. The delivered values are very accurate, however the device for performing this examination is not available in every ophthalmology practice and is usually not paid by the health insurance companies.
The intraocular pressure is normally between 10 and 21 mmHg. Values above are considered worthy of observation, but they do not necessarily have to be pathological. If you have an intraocular pressure of more than 21 mmHg, further measurements are usually carried out. This includes, for example, a daily pressure profile of both eyes at intervals of three hours. Noticeable are fluctuations in value of more than 5 mmHg in one eye or pressure differences of 5 mmHg between both eyes.
When reflecting on the fundus, it is important to assess the extent to which the retina and optic nerve have been impaired by the increased intraocular pressure, or whether they may have already been damaged.
Structures that are given special attention during the study are:
- Retinal vessels such as arteries and veins
- Optic nerve head (papilla)
- Spot of the sharpest vision (macula lueta)
In summary, conspicuous findings on these structures can provide clear evidence of elevated intraocular pressure. For this reason, the funduscopy, which is also called ophthalmoscopy, the most important tool for diagnosis.
The gonioscopy, also called slit lamp examination, mainly serves to assess the anterior segment of the eye, ie the cornea, the anterior and posterior chamber of the eye and the lens. With the help of a special microscope, the treating ophthalmologist can assess changes in the chamber angle during this examination and estimate, for example, whether there is a drainage obstruction in the episcleral vein network or if the chamber angle may be too narrow.
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Worth knowing about diagnostics and examinations
The primary goal of any glaucoma therapy is to lower intraocular pressure. In the treatment, however, a distinction must be made whether the glaucoma is acute or over a longer period of time.
Untreated, blindness threatens
A glaucoma attack, which frequently occurs in the context of an angle-locked glaucoma, is an ophthalmological emergency, which must be treated immediately, otherwise irreparable damage to the eye threatens. In the case of chronic glaucoma, it is decided from the synopsis of symptoms and ophthalmological examination results, when and with which therapy should be started. Although not so urgent, chronic glaucoma must always be treated.
1. Therapy of glaucoma
The acute angle block is an absolute emergency in ophthalmology, as it can lead to irreversible blindness in a short time. Since the symptoms of glaucoma are usually very strong, in most cases, it is treated in time in Germany. The eyesight can be obtained with it.
Range of active ingredients
The treatment of glaucoma is purely medicinal and usually shows good effects within a few hours. Most commonly used is a combination of different agents that all lower the intraocular pressure:
- Mannitol (Osmitrol®, Osmofundin®, Osmosteril®) is administered intravenously and acts via its osmotic properties lowering the intraocular pressure.
- Carbonic anhydrase inhibitors such as acetazolamide (Diamox®) or beta-blockers such as timolol (Arutimol®, Timo-Hexal®, Chibro-Timophthal®, Dispatim®, Nyogel Eye Gel®, Timo-Comod®, Timophthal®Timo-Stulln®) are also administered via the vein and cause a reduction in aqueous humor production in the eye.
- Local myotics such as pilocarpine (pilocarpine anchorpharm®, Pilot man®, Pilopos®, Sparsacarpine®) are administered as drops approximately every 15 minutes. They ensure that the aqueous humor drainage works better and work synergistically with the other substances via this mechanism.
- In addition to lowering the intraocular pressure, strong analgesics are often used, as the onset of glaucoma can cause very painful facial pain.
Following a reduction in intraocular pressure, surgical treatment of glaucoma may become necessary in some cases. Furthermore, a strict adjustment of the blood pressure should be made, since too high blood pressure can be a risk factor for the development of glaucoma.
2. Therapy of chronic glaucoma
In chronic glaucoma, time is not pushing so much. Your doctor will decide from when it is sensible to reduce the intraocular pressure and how it should look like.
Different target pressures
The decision for or against a reduction in pressure is not only dependent on the intraocular pressure itself, but also on whether there are other risk factors such as myopia and which type of glaucoma you have. For example, for chronic open-angle glaucoma, pressures below 18 mmHg are desired, while for normal pressure glaucoma the target value is 12 mmHg.
As with glaucoma, medications are the drug of choice for the treatment of chronic glaucoma. As a rule, they are administered as drops once or several times a day over a certain period of time or as continuous therapy. Only when the individual target pressure can not be achieved with the help of medical measures will operative procedures be used.
The most commonly used drugs are:
- Carbonic anhydrase inhibitor: acetazolamide (Diamox®), Dorzolamide (Dorzolamide Ratiopharm®, Dorzo vision®) and brinzolamide (Azopt®)
- Beta Blocker: Timolol (Arutimol®, Timo-Hexal®, Chibro-Timophthal®, Dispatim®, Nyogel Eye Gel®, Timo-Comod®, Timophthal®Timo-Stulln®) and betaxolol (Betoptima®)
- Alpha-2 agonists: Brimonidine (Alphagan®, Brimonidine Stada®)
- Prostaglandins: Latanoprost (Xalatan®)
Carbonic anhydrase inhibitors, beta-blockers and alpha-2-agonists all prevent the formation of aqueous humor in the eye through different mechanisms. By contrast, prostaglandins increase the outflow of aqueous humor through the episcleral veins.
Can be increased at will
In the treatment of chronic glaucoma, your doctor will usually follow a step-by-step plan. If enough drugs and doses of one stage are not enough to lower the intraocular pressure enough, the Next step is taken.
A frequently used therapy scheme is the following:
- step 1: Once a day prostaglandins or twice daily beta-blockers
- Level 2: Once a day prostaglandins plus twice daily carbonic anhydrase inhibitor or beta-blocker
- level 3: Once a day prostaglandins plus twice daily carbonic anhydrase inhibitor plus beta blocker
- Level 4: Combination of all four above-mentioned preparations in individual dose.
In most cases, chronic glaucoma can be treated very well medically. If, however, it is not possible to lower the intraocular pressure satisfactorily, or if it even rises under therapy, operative measures will be used.
3. glaucoma surgery
The surgical methods of glaucoma therapy have become very diverse and partially adapted to the particular form of glaucoma. Although they achieve good results, they are usually only used when the drug therapy for lowering the intraocular pressure has failed.
Trabeculectomy, the most widely used open angle glaucoma treatment method today, and the implantation of mini-stents are discussed in more detail below.
Trabeculectomy is a diverting procedure that is often performed today in refractory open angle glaucoma. The aim of this surgical method is to create an alternative, artificial drainage for the excess aqueous humor under the conjunctiva.
Trabeculectomy involves a small incision that connects the anterior chamber of the eye directly to the conjunctiva. From now on, the aqueous humor will not only be absorbed via the episcleral venous network, but also via the artificial drainage into the conjunctiva. The intraocular pressure can be lowered quickly and reliably using this method.
Pipeline for the aqueous humor
The procedure for implanting shunts or mini-stents is similar. As with trabeculectomy, an artificial connection is created between the anterior chamber of the eye and the conjunctiva, but it is additionally provided with a fine drainage tube so that the aqueous humor can flow out through the tube.The advantage of the method is that the diameter and length of the stent can be used to precisely determine how much additional aqueous humor should leave the eye.
Furthermore, there are methods in which the production site of the aqueous humor (ciliary body) is obliterated or reduced in size by means of ultrasound, laser or cold (cyclodestruction), so that less aqueous humor is formed in the eye. A major disadvantage of this method of operation is that it often has to be repeated several times until the desired result can be achieved. In addition, after a cyclodestruction, any other therapy can not readily be connected.
Questions and answers about the treatment
Probably the most feared complication of the green cataract is an irreversible loss of vision that can lead to complete blindness. This complication occurs creeping in chronic glaucoma, while an acute glaucoma attack can lead to the loss of sight within a short time.
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Green Star: history and prognosis
While it is difficult to prevent the onset of glaucoma, to prevent or early detect chronic glaucoma, every 40 years, you should consult an ophthalmologist every other year and have your pupil inspected and intraocular pressure measured.
It is best to inquire in advance which services your health insurance company will assume and which ones you will have to pay for yourself.
Author: Lisa Wunsch
F. Grehn: Ophthalmology, Springer Verlag, 2012.
Lehn et. al: Ophthalmology, Thieme, 2008.
Prof. Dr. Markus Kohlhaas: "Therapy and follow-up of glaucoma", https://www.bundesverband-glaukom.de/dokumente/upload/de2c9_augenspiegelglaukom%5b1%5d.pdf, last accessed on 16.01.2018.