Glaucoma refers to to eye diseases that – usually due to increased intra-ocular pressure – damage the sight nerves and with inadequate therapy can lead to loss of the field of vision and to blindness. About 1% of the population suffer from this disease, with the risk increasing at an older age. It is particular dangerous because the disease initially progresses slowly and unnoticed. Regular examination is recommended from the age of 40 in order to discover glaucoma on time.
Primary open-angle glaucoma is most common, while it doesn’t cause any difficulties for a long time; if discovered on time, it can be treated well using eye drops. Other forms include acute glaucoma, which is an urgent case and which can very quickly lead to blindness, and also congenital glaucoma and secondary glaucoma as the consequence of some other eye disease. If eye drops are not enough, treatment by laser or an operation is required.
Glaucoma (green cataract) is the general name for various eye diseases, which mostly possess the same three basic characteristics:
- elevated intra-ocular pressure
- reduced field of vision
- excavation of the papilla with loss of mass (atrophy) optical nerve
In the majority of cases, increased eye pressure plays an important role in the occurrence of glaucoma. Defects in the discharge of the aqueous humour into the anterior chamber of the eye leads to imbalance between continual production in the ciliary body and the discharge. Liquid builds up in the eye, increasing the pressure. This increased intra-ocular pressure damages mainly sensitive optical nerves. The damaged nerve tissue can then no longer send all information to the brain and so it leads to loss of field of vision, which is typical for glaucoma.
However, because there are also patients with glaucoma who have normal intra-ocular pressure, we talk also about other factors than about its causes. A certain role can therefore be played here, for instance, by defects to the repletion of optical nerves and the retina. Then it could mean a vascular disease and too high or too low blood pressure.
We usually distinguish four different forms of glaucoma:
- primary open-angle glaucoma
- primary closed-angle glaucoma (= acute glaucoma/glaucoma attack)
- secondary glaucoma, increased interocular pressure as a result of some other disease of the eye or overall illness
Incidence and risk factors
In industrial countries glaucoma is one of the most common causes of blindness. An estimate states 1% of the population as suffering from glaucoma, or at least as being strongly threatened by the onset of glaucoma. The most common form of glaucoma is primary open-angle glaucoma. The elderly are particularly prone to it. Incidence of the disease is at least eight times higher in the 70-80 year old age class than it is in 30-40 year olds. In the case of open-angle glaucoma, the following risk factors play a combined role:
- aged over 65
- common incidence in the family
- diabetes mellitus
- cardiovascular disease
- strong eye inflammation
- strong short-sightedness
- treatment with cortisone
Men and women of a younger age are affected by glaucoma with the same frequency. Acute glaucoma can, in principle, appear at any age, but the incidence of it increases with age. In the elderly, women are affected slightly more often than men. Key risk factors are:
- eyeball is too short; this often appears in the case of hypermetropia (long-sightedness)
- frequent incidence in the family
Primary congenital glaucoma arises rarely and under normal circumstances it appears in the first years of life. There is a clear disposition to it, but the exact manner of inheritance is still not known.
Primary open-angle glaucoma is asymptomatic for a long time, meaning it goes undetected by the inflicted person. In typical cases, there is not even any pain. With high intra-ocular pressure, however, because of so-called epithelial edema, coloured rings or haze can appear around light sources. By epithelial edema we understand the accumulation of liquid in the top layer of the cornea. At an advanced stage it leads to a defect in the field of vision and even to complete blindness.
Acute glaucoma is characterised by hard red eye with a pupil that is not reactive to light and accompanied by pain and sight disorders. We can often witness also general symptoms such as headache, nausea and sickness. Primary congenital glaucoma in affected children is marked by evident watering eyes sensitive to light and convulsive contraction of the eyelids. With very large eyes of newborns there is an urgent suspicion and we should definitely consult with an expert physician. Secondary glaucoma may, depending on the existing condition, be without symptoms or may be associated with all of the aforementioned symptoms.
Primary open-angle glaucoma
For a reliable diagnosis of primary open-angle glaucoma it is important in every case to assess the intra-ocular pressure, the field of vision and the papilla of the optical nerve. For diagnosing glaucoma, sometimes many years of checks of its progress are required with documentation of all findings.
The aforementioned symptoms are a key sign of the existence of acute glaucoma. An eye doctor can then easily confirm the diagnosis by measuring intra-ocular pressure and by examining the front segments of the eye and the eye chamber angle.
Primary congenital glaucoma
A reliable diagnosis of primary congenital glaucoma can often be determined only by examining the inflicted child under narcosis.
With secondary glaucoma, increased intra-ocular pressure is at the forefront of diagnosis. The diagnosis then arises from existing diseases.
The upper threshold of intra-ocular pressure is approximately 21-23 mm of Hg (Hg = mercury). The pressure has a tendency to rise with older age. We must mention that in spite of intra-ocular pressure at the threshold of the norm, glaucoma could still be present. In these cases, although the intra-ocular pressure is static at the normal thresholds, individually it is too high for the affected eye and causes corresponding damage. On the other hand, increased pressure might not necessarily mean glaucoma is present. In this case, the individual threshold of tolerance of the respective eye is higher than normal.
Medicamentous treatment is in first place in treatment aimed at reducing intra-ocular pressure in the case of primary open-angle glaucoma. The drugs applied are normally eye drops. There are various classes of active substances available, which can also be combined. Where medicamentous treatment is insufficient, laser treatment can be used in certain cases. The pressure reducing effect is only slight, however, and not permanent. Then the alternative is to have an operation. Operations are usually conducted under local narcosis, with the creation of artificial discharge for the aqueous humour.
Acute glaucoma is an urgent condition and must be treated immediately. Primarily, it requires medicamentous reduction of intra-ocular pressure followed by an operation (alternatively, by laser). Treatment of congenital glaucoma is always determined progressively. Treatment of secondary glaucoma depends on the existing disease, but is basically determined according to the principles outlined above.
Where primary open-angle glaucoma is concerned, from the age of 40 every person should have a prophylactic examination at an eye doctor, including measurement of intra-ocular pressure at least once every three years so that timely treatment can be started to reduce pressure. Risk patients should undergo preventive examinations more often. Patients who have already suffered some bruising or other injury to the eye should have their eye pressure checked once a year for a long time because such injuries can lead to secondary glaucoma. In 5 to 10% of all people, longer treatment with eye drops containing cortisone or other drugs containing cortisone can lead to so-called cortisone glaucoma as a specific form of secondary glaucoma. These patient should therefore have their eye pressure checked.
In principles it should be noted that every kind of glaucoma that is not treated will eventually lead to blindness in the affected eye. Damage that has already occurred can no longer be eradicated despite intensive therapy. Primary open-angle glaucoma is a chronic pathological process, which progresses more or less slowly, over years and even decades. With suitable therapy this process can be halted or slowed down. Untreated acute glaucoma will lead quickly to blindness in the majority of cases. If discovered on time, however, and if adequately treated, it has a very good prognosis. Despite timely treatment of congenital glaucoma, partial damage often remains with reduced sharpness of vision, but complete blindness can mostly be prevented. The prognosis of secondary glaucoma depends on the existing disease.