In diseases such as glaucoma, the intraocular pressure is greatly increased. In Germany, more than 900,000 people suffer from this disease, although the number of unreported cases is probably much higher. This results in damage to the optic nerve, which can only be prevented by regular checks of intraocular pressure.
What is intraocular pressure?
The pressure in the eye (tensio) is of important significance. Also called intraocular pressure, it names the physical pressure exerted on the inner wall of the eye. It is regulated by the aqueous humor outflow and inflow in the eye. Formed within the medial eye membrane – more precisely, in the ciliary body – aqueous humor enters the eye through the pupil and regulates intraocular pressure there. Usually, the normal value is between 10 and 21 mmHg. With the so-called tonometry, a physician can determine the pressure and thus decide whether it is within the average range. The term tonometry is used by specialists to refer to various measurement methods. These include, for example, non-contact tonometry, in which the cornea is flattened with the aid of a blast of air. Depending on the resistance, the internal pressure of the eye can be determined. Experienced physicians achieve an accurate value of up to 2 mmHg by estimation. A slight pressure is applied to the closed eye. However, the intraocular pressure fluctuates throughout the day, which is why a regular measurement is useful in case of complaints.
Anatomy and origin
The ciliary body lies between the iris and the lens. The epithelium of the ciliary body is responsible for the formation of the regulating aqueous humor. Epithelium is the term used by physicians to describe the layers of tissue and cells. This is where the aqueous humor enters the anterior chamber of the eye between the iris and the lens. Most of it flows into the episcleral venous system via chambers and channels. The amount of aqueous humor determines the pressure in the eye and is therefore also responsible for the alignment of the photoreceptors in the eye. Persistent misregulation of intraocular pressure can lead to damage to the eye. For example, a steady intraocular pressure of more than 21 mmHg is harmful to the optic nerve, which lies behind the vitreous and is responsible for transmitting information to the brain.
Function and tasks
The internal pressure of the eye plays a crucial role in clear vision. It has an important function within the complex processing of images. The pressure is responsible for maintaining a constant distance between the lens, retina and cornea and curves the surface of the cornea. It thus gives it its characteristic shape and maintains it permanently. If the pressure is within the normal range, the optic nerve can thus transmit the recorded images to the brain, where they are further processed. Diseases of the chamber angle lead to the fact that the supply of chamber water is disturbed. The intraocular pressure rises and thus triggers damage. Thus, the mechanisms in and around the eye interact and depend on each other for clear vision.
Diseases
In addition to diseases of the chamber angle, increased aqueous humor outflow can also lead to an imbalance. If more aqueous humor is drained than the eye can form, the pressure within the eye increases. Every person has a personal tension tolerance, with which a slight increase in intraocular pressure can be tolerated. These limits are individual. If the increase in pressure persists over a longer period of time and continues to rise, severe damage to the optic nerve is to be expected. On the other hand, even a normal value can lead to glaucoma. This is related to a lowered personal tolerance level and must be determined individually with a medical professional. In order to assess all glaucomas, it is therefore important not only to pay attention to the intraocular pressure, but also to address any complaints the patient may have. Regular examinations are recommended from the age of 40, as there are a number of risk factors that promote an increase in intraocular pressure and thus the development of glaucoma. The higher the pressure, the higher the risk of permanently damaging the optic nerve and developing glaucoma. If patients exhibit increased intraocular pressure but no changes in the optic nerve, experts refer to this as ocular hypertension. Incidentally, there is no correlation between blood pressure and intraocular pressure. The daily range and treatment, on the other hand, are similar.Intraocular pressure is usually highest in the morning. However, these guideline values are cancelled out in glaucoma patients. Treatment can be done in different ways. On the one hand the production of aqueous humor can be increased, on the other hand it is also possible to regulate the outflow. In most cases, the normalization or regulation of the outflow and inflow of aqueous humor is achieved by administering medication. The eye drops used for this purpose are called antiglaucomatous drops. In addition, beta-blockers also work successfully against increased intraocular pressure. In addition, various other medications, such as alpha agonists, can be used to lower the pressure. In addition to these methods, surgical interventions are also possible. They are performed if the administration of the preparations does not achieve any result or achieves an unsatisfactory result. In some cases, both are used in parallel. One possibility of surgical treatment is trabeculotomy. In this case, the operation time is usually only half an hour. During the procedure, the surgeon will restore the aqueous humor outflow to normal by probing the affected annular canal. Another option is a variety of laser treatments designed to achieve the same result.
