Diagnosis

The intraocular pressure

synonym

Tonometry

English: intraocular pressure measurement

Definition of intraocular pressure

An intraocular pressure measurement is understood to mean different mechanisms for measuring and determining the pressure that is present in the anterior segment of the eye.

The development of intraocular pressure

The eye, like pretty much every part of our body, depends on a sufficient supply of fluids. On the one hand, so that there is no risk of dehydration, but on the other hand, because the liquid and the substances dissolved in it ensure the supply of nutrients to some parts of the body that would otherwise not be adequately supplied by the blood.

The anterior chamber is located in the anterior segment of the eye between the cornea and the lens of the eye. There is a liquid in it, which is produced in certain quantities and drained off in corresponding quantities. This is the so-called aqueous humor, which supplies the cornea with sufficient nutrients and maintains its shape through the pressure. The aqueous humor is formed in the eye itself, namely in the ciliary body, a ring-shaped section of the middle skin of the eye (which is not only responsible for the production of aqueous humor, but also for the attachment of the lens and for near accommodation).

The aqueous humor flows from the ciliary body into the anterior chamber of the eye and from there is conducted through small channels into the bloodstream. In a healthy eye, as much aqueous humor is always formed as is released back into the blood, so there is a fine balance between production and drainage. In diseases of the eye and disorders of the aqueous humor circulation, this balance can be disturbed and the aqueous humor pressure falls or rises, which is why this can be used as a good indicator of diseases that affect the eye.

The liquid also exerts a more or less strong pressure (Intraocular pressure) on the entire eyeball and on the Vitreous which in turn transfers the pressure to the fundus. The normal intraocular pressure is 15.5 mmHg. However, this intraocular pressure can fluctuate. The normal values of intraocular pressure are between 10 mmHg and 21 mmHg codified.
The aqueous humor is absorbed by the ciliary epithelium in an amount of approx. 2.4 mm³ formed in the minute and released into the posterior chamber. It washes around them lens and finally flows into the anterior chamber. The aqueous humor is then filtered off through the trabecular system in the chamber angle and from there it enters the so-called Schlemm's canal. From there it finally flows through small channels into the veins of the Conjunctiva and thus into the blood system.

The aqueous humor production is subject to a day-night rhythm and is reduced by approx. 40% at night. The functions of the aqueous humor include nutrition the lens and the cornea, maintaining the shape of the eyeball with the corresponding constant curvature of the front part of the eye (important for the refraction of light), and detoxification of the inside of the eye (interception of free radicals). Furthermore, the aqueous humor also serves as a lymph substitute, since the eye no own Lymph fluid owns.
Reasons for an increased intraocular pressure are exclusively a disturbance of the drainage in the trabecular system and never an excessive production of the aqueous humor. The reason is usually pathological changes in the trabecular system.

Values / normal values

The intraocular pressure comes about through the balance between production and drainage of the aqueous humor. This is a liquid made by certain cells in the eye. The intraocular pressure is important for the uniform Curvature of the cornea, as well as for maintaining the correct spacing between lens and cornea.

The intraocular pressure can be measured. Of the Normal value amounts 15.5 mmHg (Millimeters of mercury), where the Lower limit at 10 mmHg and the Upper limit the normal intraocular pressure range 21 mmHg lies. However, the intraocular pressure fluctuates between 3-6mmHg even in healthy people. Therefore, a one-time intraocular pressure measurement is only to be viewed as a snapshot and does not necessarily rule out a disease with normal values. In addition, the intraocular pressure value can be falsified by a particularly thick cornea, which an ophthalmologist should take into account.

The highest levels of intraocular pressure are reached around midnight and in the early morning hours, during the day the intraocular pressure drops slightly. In addition, intraocular pressure is generally higher in older people than in young people.

Is there a Drainage disturbance at the chamber anglel before where the aqueous humor can normally drain, the intraocular pressure increases (ocular hypertension) as the liquid builds up in the eye. This leads to an increase in pressure over 21mmHg, this can be harmful to the eye in the long run. Of the Optic nerve and the Retina (retina) can be permanently damaged by the compression, so Loss of vision up to blindness can result. Temporarily can eye withstand higher pressures without being damaged. This is known as Tension tolerance. However, the higher the intraocular pressure and the longer this pressure increase lasts, the higher the risk of permanent damage to the visual system. Since people over the age of 40 are particularly affected by an increase in intraocular pressure, it is advisable to have the pressure checked regularly from this age onwards.

However, intraocular pressure can also too low be (ocular hypotension). Usually this is due to one of them Underproduction of aqueous humor. This is very dangerous as the intraocular pressure is necessary to fix the retina in place. If the pressure is not high enough due to a lack of aqueous humor, it can result in a Retinal detachment with resulting Blindness come. The fastest possible therapy is required.

In glaucoma, the intraocular pressure is increased. One differentiates between one chronic glaucoma, which can gradually develop over weeks, months or even years, and the acute attack of glaucoma. In a glaucoma attack, the intraocular pressure suddenly rises sharply, sometimes to values of over 30 or 40 mmHg. Patients complain of a reddened, painful eye, and their vision only works to a limited extent or not at all. The pupil no longer reacts to the strength of the incident light, so the patients are also very sensitive to light. The eye feels, due to the increased intraocular pressure, rock hard on and very often there are side effects like a headache, nausea and Vomit.

This is a medical emergency in which lowering intraocular pressure is the top priority of therapy. As described at the beginning, the intraocular pressure can rise either due to a disturbed production or a disturbed drainage. It is rare that the ciliary body produces too much aqueous humor. In most cases, increased intraocular pressure is due to the fact that the drainage path in the anterior chamber through which the aqueous humor flows into the blood circulation is no longer open wide enough and the aqueous humor accumulates in the eye. If this is the case and the patient develops glaucoma, one speaks of a so-called Angle-closure glaucoma. The angle in the name refers to the small drainage channel of the aqueous humor.

Measure intraocular pressure

Of the Intraocular pressure should be checked regularly as intraocular pressure is too high Optic nerve can constrict and thus damage it. This can in the worst case scenario too blindness to lead.

The measurement of intraocular pressure is called Tonometry designated. There are different procedures here.

A very outdated and not very accurate method is impression tonometry. The patient has to put his head back and the tonometer is placed directly on the cornea to measure the intraocular pressure. Depending on how heavy the weights have to be that lead to a flatter cornea, you can determine the intraocular pressure.

Also a little out of date, but still quite accurate by 2 mmHg, is palpation of the closed eye with the fingers (Palpation). After being shown and explained what to look for, the patient can easily do this himself at home. Also there is one Self-tonometer, which works on the same principle as an applanation tonometer. The patient is thus able to take a relatively exact measurement of the intraocular pressure from home without having to visit an ophthalmologist (the necessary contact with the cornea can be compared to inserting a contact lens).

The applanation tonometry according to Goldmann is much more precise. First, the eye is anesthetized with a local anesthetic, and then a fluorescence-marked solution is instilled into the connective tissue sac of the skin. Now you put on a measuring prism that is attached to a spring balance. The cornea (Cornea) now creates a certain pressure on this measuring prism. The pressure that is required to bend the measuring prism is the intraocular pressure that can be read from the spring balance. This standard procedure poses next to no risk for the patient. Only in very rare cases can the smallest corneal injuries or infections of the eye occur.

In special cases, for example, if the eyes are already damaged or direct contact with the cornea would not be advisable for other reasons, the intraocular pressure can also be measured with the help of a Non-Contact Tonometers determine. This works with a blast of air, which flattens the cornea very slightly so that the doctor can then calculate the intraocular pressure based on the duration and strength of the required air flow. However, this method is not the most reliable and is used less often.

Dynamic Contour Tonometry is another way of measuring intraocular pressure. In comparison to all other procedures, the cornea is not flattened. A certain pressure is created between the measuring head and the cornea. This pressure is the intraocular pressure. Since the measurement method is very precise and can also be repeated frequently, this is the method of choice.

causes

As mentioned earlier, the Measurement of intraocular pressure carried out as an early diagnosis test if a glaucoma is suspected (regularly from a certain age). Because with glaucoma, the previously described balance between the production of aqueous humor and the outflow of aqueous humor is disturbed and the intraocular pressure rises. A moderate increase in intraocular pressure goes unnoticed by the patient himself, as it does not cause pain, nor does it lead to visual field failures or other visual impairments.

Only when the Optic nerve has already been damaged, complaints arise, then, however, it is already too late to restore the affected optic nerve and one can only try to keep the damage as low as possible. However, measuring intraocular pressure is not only suitable for the early detection of glaucoma. It is also advisable to have it checked at certain regular intervals after all other injuries to the eye, as there is generally a risk of a so-called eye injury after an injury to the eye Secondary glaucoma forms. Also by taking cortisone Medication, especially eye drops containing Costa Rica, can help develop a Cortisone glaucoma to lead. In this case, too, regular intraocular pressure monitoring can reveal damage at an early stage.

Assumption of costs

There has been, however, since the year 2015 a certain conflict with the statutory health insurance in Germany. Its representatives do not consider intraocular pressure measurement to be of sufficient benefit as an early preventive check-up in order to be able to determine increased intraocular pressure, which in most cases leads to glaucoma (glaucoma), and have therefore decided to use tonometry as an individual health service (IGeL services) to be settled. Recognized ophthalmologists recommend every patient who has reached the age of 40 to have their intraocular pressure values measured and checked annually. So can a beginning glaucoma can be recognized and treated at an early stage and major damage to the optic nerve and thus to the eyesight is avoided. However, if there is already a justified suspicion that a patient suffers from glaucoma and the tonometry thus serves as a follow-up examination, the statutory health insurance company will also pay for the examination.

Risk of increased intraocular pressure

If the intraocular pressure rises, this leads to the pressure gradient being passed on via the vitreous humor inside the eye, which in turn passes the pressure on to the fundus with the retina and optic nerve. The optic nerve only tolerates a certain pressure without damage. Increased intraocular pressure is usually painless, and damage to the optic nerve is often recognized late. This makes it urgently necessary to have the intraocular pressure checked regularly by means of an intraocular pressure measurement.

Increased intraocular pressure / glaucoma

Is there a Drainage disorder at the so-called chamber angle of the eye, the produced aqueous humor can no longer flow properly. It comes to Fluid build-up in the eye and thereby to one Pressure increase.

From one Intraocular pressure over 21 mmHg is called increased intraocular pressure. This is dangerous because the pressure is too high Optic nerve and the Retina damage and permanently Blindness can lead. Elevated intraocular pressure is a major risk factor for developing a Glaucoma (cataract). This leads to the loss of nerve fibers of the optic nerve, which soon becomes apparent Visual field loss and finally becomes noticeable through complete blindness of the affected eye. However, increased intraocular pressure is not an essential requirement for the development of glaucoma. About 40% of glaucoma patients have completely normal intraocular pressure (Normal pressure glaucoma). Nevertheless, increased intraocular pressure is often involved in the development of glaucoma. It is particularly unfavorable in combination with low blood pressure in the optic nerve, as it causes the loss of nerve fibers to progress faster and the glaucoma can worsen more quickly.

The most common form of glaucoma is the so-called primary chronic glaucoma, which manifests itself preferably from the age of 40. Over time, patients develop a drainage disorder in the corner of the eye as a result of aging, which makes it harder for the aqueous humor to drain away. Since this process develops over several years, the intraocular pressure increases slowly but steadily over time. As a rule, those affected have no symptoms.

However, if the chamber angle is suddenly misplaced and this causes the aqueous humor to jolt up, this leads to a Glaucoma attack. This suddenly creates extremely high intraocular pressures (up to 70mmHg) and those affected suffer from severe a headache, Eye pain and partly too nausea and Vomit. The affected eyeball is usually very hardened when palpating.

Since most patients with increased intraocular pressure do not experience any symptoms, even if they have already suffered damage to the eye, regular preventive examinations at the ophthalmologist are the only way to recognize and treat increased intraocular pressure early enough. In this way, most of the consequential damage and blindness in affected patients can be prevented in most cases.

Lowering intraocular pressure

It comes to one increased production of aqueous humor or there is a disproportion between inflow and outflow, this can lead to a increased pressure in the eye to lead.
This increased intraocular pressure can on the one hand the Optic nerve harm what to Visual field defects leads and the other reason for the glaucoma (glaucoma) be.

That is why it is very important to lower the intraocular pressure. Now there are different ways to lower intraocular pressure. For one thing, you can eye drop use. There are different varieties here. There are for example Carbonic anhydrase inhibitorsthat decrease aqueous humor production.
Then there are so-called beta blockers or alpha blockersthat block various channels and thus also lower the aqueous humor production and thus the intraocular pressure.
You can also use the Improve the outflow of aqueous humor or normalize. This can be done using a minor intervention respectively. Here, the doctor cuts part of the with a trabectome Trabecular meshwork which often becomes stiffer with age and therefore the Chamber drainage very difficult.
A Trabectoma looks like a ballpoint pen with a small electric knife and a suction and infusion channel at the end. This little intervention is done with local anesthesia carried out and usually takes no longer than 10 minutes, but achieves great success. Most patients need to do so much less eye drops use.
A major intervention, however, is that Trabeculectomy. This is a major operation in which the surgeon does the Large areas of the conjunctiva cut open and thereby creates an artificial drainage for the aqueous humor. Even after this operation, patients are much less dependent on eye drops to lower intraocular pressure, but this is Post-treatment very intensive and can with one decreased eyesight be connected.

Another way to lower intraocular pressure is one Laser treatment. Here the Chamber angle Treated with a laser beam, this drains more aqueous humor. However, this method is only suitable for not too advanced disease.

Finally there are those Desolation-icing. Here the so-called Ciliary body deserted. The ciliary body is responsible for the production of aqueous humor. By getting him partially deserted, one can greatly reduce the aqueous humor production and thus also the intraocular pressure.

It is important to mention that one surgical intervention only at; only when advancing disease is being used. In the case of slightly increased intraocular pressure, eye drops are completely sufficient!

Naturally lower intraocular pressure

Of the Intraocular pressure can be abnormally increased for various reasons. The cause can for example both in the ingestion of certain Medication, as well as in one Disturbance of the drainage of the aqueous humor lie in the eye. Depending on how high the intraocular pressure is, the Optic nerve and the Retina are permanently damaged, which is why a medical therapy is advisable.

However, there are also ways of using intraocular pressure natural means to lower. So are homeopathic eye drops with the ingredient Euphrasia (Eyebright) available in the pharmacy. These can help lower the pressure. Eyebright is also available as a tincture in combination with other medicinal herbs (Johannis herbs, Mistletoe essences) available for internal use.

In many cases, too, has use alternative healing methods, like for example acupuncture, Reflexology and Kinesiology proven. A blockade of the Cervical spine can also cause increased intraocular pressure. Spinal exercises and targeted physical therapy can help. Certain eating habits can also promote increased intraocular pressure. Hence it is recommended to click on Caffeine consumption largely to do without and one vitamin-rich diet to pay attention. For example, they have a positive influence on intraocular pressure selenium, zinc and the Vitamins A, B, C and E..

Pollutants in tobacco smoke are also irritating to the eye. Therefore, smoking is not beneficial for people with increased intraocular pressure.

A positive effect has, however, regular Endurance training. This can also reduce increased blood pressure, which is often the cause of increased intraocular pressure.

In some cases, too Dental problems an impact on the pressure in the eye. If there are problems with the dental apparatus, they should be medically rehabilitated if possible. In some circles, too Amalgam fillings believed to be bothersome to intraocular pressure. Under certain circumstances, the old fillings can be replaced.

However, if the intraocular pressure is strongly and permanently increased, conventional medical treatment is usually unavoidable. Effective medication or surgical interventions are used to bring the intraocular pressure back to a normal level.