Glaucoma: Causes and Treatment of Glaucoma
Glaucoma, also known as "green star," is one of the most common causes of blindness worldwide. In Germany alone, over half a million people suffer from the disease. The reason is the death of nerve fibers in the eye, for example due to excessive intraocular pressure. Regular check-ups with an ophthalmologist are therefore particularly important in old age - because various treatment approaches can often stop the disease from progressing and prevent blindness.
Scotoma: Irreparable Damage
It doesn't hurt. It comes on gradually. The field of vision becomes smaller, narrowing from the outside inwards, whole areas or individual objects disappear in the fog - and the brain covers up the secret attack on the ability to see by filling the resulting gaps with memory images. By the time glaucoma patients notice the impairments in their ability to see, the damage is usually already irreparable. The ophthalmologist who diagnoses the so-called "scotomas" - the name given to the visual field defects - during a perimetry can only try to halt the progression of the disease. The death of sensory cells must be stopped and the normal metabolic activity of the eye must be restored. Otherwise, even today, the patient is at risk of going completely blind.
What risk factors play a role in glaucoma?
There is a reason why glaucoma is a widespread disease, not to say a widespread illness. Cardiovascular disease, low or high blood pressure, high blood fat levels, diabetes, various medications, smoking, inflammatory changes and even genetic predisposition - all of these factors lead to an increased risk of developing glaucoma. A healthy and varied diet, plenty of exercise and the successful treatment of pre-existing conditions can reduce the risk. The most important thing, however, is regular check-ups by an ophthalmologist, especially after the age of forty.
When eye pressure rises: A transport problem
The main cause of glaucoma is excessive intraocular pressure. But how does this happen? So-called aqueous humor is formed in the anterior chamber of the eye. It transports oxygen and nutrients to important parts of the eye, such as the lens and cornea, which do not have blood vessels of their own. The "used" aqueous humor is transported away via a system in the chamber angle, the so-called trabecular meshwork and Schlemm's canal. If this system no longer functions properly, the aqueous humor builds up in the anterior chamber of the eye - and the pressure increases. This increased pressure disrupts the supply to the sensitive nerve cells, which then die. The eye pressure is measured by the ophthalmologist using a so-called applanation tonometer, which can be used to determine how much force is needed to deform the clear layer of skin in front of the pupil.
What types of glaucoma are there?
Depending on the anatomy or cause of glaucoma, four different main groups are formed:
- In primary open-angle glaucoma, the drainage of aqueous humor is disrupted by deposits (plaques).
- Narrow-angle glaucoma is characterized by the fact that the anterior chamber of the eye is so shallow that the aqueous humor can no longer reach the “drainage system” in the corner of the eye when the pupils are dilated.
- Congenital glaucoma can be traced back to a maldevelopment of the eye. In this case, too, the aqueous humor cannot be drained properly.
- Secondary glaucoma is a drainage disorder caused by illness or injury. In this case, scar tissue or inflammation, for example, prevent the aqueous humor from draining away.
Which medications help against glaucoma?
Since increased intraocular pressure is the main cause of glaucoma, this is where drug treatment comes in: it is intended to reduce the pressure. Two different strategies are available here. Firstly, it is possible to prevent the excessive production of aqueous humor. Beta blockers are often used first, but so-called carbonic anhydrase inhibitors and alpha agonists are also used. Secondly, medication can be used to support the drainage of excess aqueous humor. Prostaglandins and cholinergics are used in this case. The treating doctor decides which medication and which combination promises the best treatment success based on the patient's age, the progression of the disease or possible intolerances. Normally all of these medications are applied directly as eye drops in order to achieve the most local effect possible. Nevertheless, side effects can occur, for example if they enter the nasopharynx via the tear ducts and are absorbed there via the mucous membranes. Irritation or redness can also occasionally occur in the eyes themselves.
How do I use eye drops for glaucoma prophylaxis?
To prevent germs from entering the eyes, users should wash their hands thoroughly before administering the medication. If you wear contact lenses, these should be removed for application. Then you should tilt your head back and pull the lower eyelid down slightly. Then hold the applicator briefly over the eye without touching it. Then drip the recommended dose into the lower eye region. Then close your eyes without pressing them tightly shut. It is recommended that you keep your eyes closed for a few minutes after instilling the medication and apply light pressure to the inner corners of the eyes with your fingertips. This reduces the chance that the medication can get into the nasopharynx. However, many users have problems even applying the medication correctly to the eye - especially for older patients. Ophthalmologists and self-help groups offer training and practice opportunities for this.
Can glaucoma be corrected through surgery?
Unlike cataracts, there is no operation that can reverse the progression of glaucoma. Nevertheless, in some cases surgery is the method of choice to halt the progression of the disease. Trabeculectomy, in which the doctor removes a tiny part of the sclera and iris, has been used for many years. This is intended to improve the drainage of the aqueous humor in order to permanently reduce the intraocular pressure. A more modern procedure is the minimally invasive widening of the drainage canal using small steps. This procedure is mainly used for mild cases of glaucoma. Compared to trabeculectomy, the risk of scarring is lower with this procedure. Another option is surgery with a laser. Laser surgery can also improve the drainage of the aqueous humor. Alternatively, the laser can also reduce its production.
