Glaucoma is a disease of the eye colloquially known as “glaucoma”. Most diagnosed cases are so-called high-pressure glaucoma, which is associated with increased intraocular pressure. However, normal-tension glaucoma (also known as low-tension glaucoma) can also be present, in which the eye pressure is not elevated. Normal-tension glaucoma differs markedly in some respects from the more commonly observed high-tension glaucoma, which is why it requires special attention.
What is normal-tension glaucoma?
Normal-tension glaucoma or low-tension glaucoma is a chronic disease of the eye. Left undiagnosed, it can lead to severe, irreversible damage to the eye with permanent consequences such as optic nerve damage, visual field loss, and blindness. The disease can occur at any age. In some cases, glaucoma is also congenital, in which case there is, for example, an undeveloped chamber angle. Even though high-pressure glaucoma is diagnosed much more frequently, namely in 70 to 90 percent of cases, experts now assume that almost every second glaucoma in Europe is normal-pressure glaucoma. Accordingly, many patients do not know that they suffer from this disease. For this reason, it is often not recognized until serious consequences have already occurred.
Causes
Unlike hypertension glaucoma, which is much more common and is characterized by increased intraocular pressure and can damage the optic nerve in this way, normal-tension glaucoma has other, less obvious causes. Most often, these are vascular in nature. Various forms of fluctuating blood pressure that tends to be low (hypotension) can trigger normal tension glaucoma. Flammer’s syndrome can also be a cause, a misregulation of the blood supply. Thus, in addition to many other organs, the sensitive small vessels of the eye can be particularly affected. The fluctuations in blood pressure result in a lack of nutrient supply to the eye. Sleep apnea patients in particular, who suffer from constant breathing pauses at night, are at risk for developing normal pressure glaucoma.
Symptoms, complaints, and signs
Normal-tension glaucoma does not initially cause symptoms because neither form of glaucoma causes pain. They are also not initially detected during preventive examinations consisting of the measurement of eye pressure, which are often performed with a so-called tonometer. All forms of glaucoma can damage the optic nerve and gradually lead to visual field limitations and even complete loss of vision. Therefore, one symptom is visual deterioration, which, however, due to its slowly progressive course, is usually not detected by the patient himself or is detected very late.
Diagnosis and course of the disease
Tonometry, in which the patient’s eye pressure is measured by means of a small puff of air delivered into the eye, is only suitable for detecting high-pressure glaucoma and is therefore not indicated for diagnosing normal-pressure glaucoma. The ophthalmologist also has the option of using opthalmoscopy to examine the back of the eye. Here he can detect typical glaucoma damage, even if the eye pressure was inconspicuous in tonometry. Typical damages are, for example, indentations and papillary rim hemorrhages. Furthermore, perimetry, the so-called visual field examination, can provide important information for the diagnosis. Here, it can be detected whether typical deficits are present in the peripheral area of the visual field. The measurement of the optic nerve by the so-called Heidelberg tomograph (scanning laser tomography) is also possible. In cases of late detected glaucoma, this may prove useful. Other diagnostic procedures include OCT (optical coherence tomography), GDx (scanning laser polarimetry), and RTA (retinal thickness measurement). All of these imaging procedures are in the area of individual health services (IGeL) and, with a few exceptions, must be paid for by the legally insured patient. Since low-pressure glaucoma can be triggered by fluctuating blood pressure, a 24-hour blood pressure examination is often ordered by the physician. For this, the treating ophthalmologist and the patient’s general practitioner exchange information by means of a referral.
Complications
Although an affected person does not feel ill, regular use of the drops prescribed by the physician is important to stabilize intraocular pressure.When side effects occur, here the German Medical Journal lists above all changes in taste, lowering of blood pressure and drowsiness, the patient should not simply discontinue the medication, but always consult his doctor first. There are many different drugs that can lower intraocular pressure, so often a change of drug can help. A kind of “natural therapy” against normal pressure glaucoma are the so-called “radical scavengers”, which are contained in many vegetables. Their content is also particularly high in green tea, dark chocolate and red wine. Dietary supplements that are often prescribed when glaucoma occurs include calcium channel blockers and magnesium granules. A diet-conscious patient can avoid them by avoiding salty foods and foods high in animal protein and phosphate. Sunflower seeds, almonds and walnuts have a high magnesium content. Scientists go so far as to use the phrase “sick eye in a sick body” for normal tension glaucoma. However, this also means that an affected person can do much to stabilize his or her intraocular pressure and the adjacent vessels.
When should you see a doctor?
If there is a gradual change in vision, a visit to the doctor is recommended. Basically, vision should be measured at regular intervals. In this way, abnormalities can be noticed as quickly as possible. Since normal tension glaucoma is rarely noticed in the early stages, it is advisable to participate in the preventive examinations offered. If complaints and irregularities of vision occur in everyday life, these should be examined. Nearsightedness, pain in the eye or a feeling of pressure inside the head are signs of an existing disease and must be clarified by a doctor. If persons or objects are perceived blurred or outlines can no longer be seen in the usual quality, a visit to the doctor is necessary. If the affected person notices that his vision is reduced in direct comparison to the vision of his fellow human beings, he should consult a doctor. If minor accidents occur in everyday life, this may be related to reduced vision. There is cause for concern, because in the further course of the disease, there is usually an increase in symptoms. Headaches, sleep disturbances, an inner restlessness or behavioral problems indicate discrepancies in the organism. The symptoms should be discussed with a physician so that a cause investigation can be initiated.
Treatment and therapy
Treatment of normal tension glaucoma consists primarily of finding the actual cause and its therapy. This requires close cooperation between the ophthalmologist and the treating general practitioner or internist. A high-salt diet can lead to an increase in the blood pressure level, which is currently a common treatment approach depending on the underlying disease. However, this is not suitable for all patients, especially if there are other underlying diseases. While the therapy of high-pressure glaucoma generally consists of lowering the intraocular pressure by means of eye drops, this method is sometimes also used for normal-pressure glaucoma, even if the intraocular pressure is basically not elevated in this case. This is because a low intraocular pressure leads to a better supply of nutrients to the eye. Frequently prescribed drugs in this case are miotics, which constrict the pupil and thus dilate the vessels so that the pressure-generating aqueous humor can drain off. Prostaglandin derivatives, known by the trade name latanoprost (R) and others, also improve aqueous humor flow.
Outlook and prognosis
Excessive intraocular pressure can have several causes. These are crucial for the further course of the disease as well as the prognosis. Cures as well as chronic developments are conceivable. In all circumstances, comprehensive medical care should be sought, otherwise further deterioration of vision will occur and the general risk of accidents will be significantly increased as a result. In addition, the causative disorder must be treated, as life-threatening changes may occur. With drug therapy, the internal pressure is normalized in most patients. Often a lifelong treatment is necessary, because the normal pressure glaucoma has developed chronically.Discontinuation of the medication consequently leads to a relapse. If the complaints occur due to sleep apnea, it must be clarified whether this can be completely cured. With the relief of the symptoms of the underlying disease, a decrease of the health complaints for the impaired vision is also possible. A complete freedom from symptoms can therefore be achieved depending on the underlying disease. In the case of diseases of the circulatory system and thus irregularities of the blood pressure, this must be medically treated. As soon as the values are within the normal range, the internal pressure of the eye returns to normal. However, a return of symptoms is to be expected as soon as a blood pressure problem arises again.
Prevention
Normal-tension glaucoma is very difficult to prevent. Targeted prophylaxis can hardly be given here. Therefore, prevention lies in the observation of the causes that may be present as an underlying disease. Sleep apnea patients, patients with blood pressure fluctuations and those with Flammer syndrome are considered to be particularly at risk and should be monitored regularly by an ophthalmologist. Regular glaucoma screening by an ophthalmologist is also recommended, although this is not covered by statutory health insurance; the costs are borne by the patient. An accumulation of glaucoma within the family is another risk factor for contracting glaucoma, which is why intensive preventive care is advisable here as well. The better the patient is informed about his underlying disease, the sooner normal tension glaucoma can be detected.
Follow-up
If normal-tension glaucoma is treated surgically, conscientious follow-up care is required. Usually, intensive aftercare takes about two weeks. This usually involves the administration of eye drops. Sometimes the patient also receives eye injections near the eyeball or eyeball massages. Even after outpatient surgery for glaucoma, the patient is observed until he is able to go home. However, he is not allowed to sit behind the wheel of a car himself. If he uses a public transport, the accompaniment of another person is recommended. Alternatively, a cab can be taken. The ophthalmologist prescribes an eye ointment or eye drops to the patient for follow-up treatment. It is important to use these consistently and regularly. In some cases, a painkiller is also taken in the first few days after the procedure. The subsequent check-ups also play an important role in aftercare. The patient is given an appointment for the next examination on the day of the operation. This appointment should be kept without fail. As a rule, the eye bandage is removed at this time. During the follow-up examinations, the ophthalmologist checks the course of healing. Among other things, the postoperative findings and visual acuity are checked. Due to the operation, the eye initially reacts particularly sensitively to mechanical damage. Therefore, the patient should temporarily refrain from using shampoos, soap or skin creams.
What you can do yourself
Those who have been diagnosed with normal tension glaucoma should first make lifestyle changes. In addition to regular exercise, which regulates intraocular pressure, a vitamin-rich diet is recommended. Fruits, vegetables and the like promote blood flow to the eyes, which can improve vision. Smokers should stop smoking and, if possible, completely abstain from nicotine in order to avoid further strain on the eyes. If the symptoms increase despite all the measures taken, medical advice is always required. The physician may be able to give further tips or prescribe a suitable preparation to alleviate the visual complaints and improve the well-being of the person affected in the long term. Finally, possible triggers for the development of normal tension glaucoma must be found. The eye condition can occur due to eye strain, such as that affecting office workers and people with excessive exposure to pollutants. Excessive sun exposure and dehydration are also possible causes that need to be identified and corrected. Although normal tension glaucoma itself cannot be cured, the risk of going blind from the disease can be greatly reduced. Anyone who wears a suitable visual aid in addition to the above-mentioned measures optimally supports the drug therapy.
