Intraocular pressure

When intraocular pressure ( synonym: intraocular pressure, medical: Tensio ) is defined as the physical pressure exerted inside the eye wall. It causes a constant smooth curvature of the corneal surface, a constant distance between the cornea ( cornea), lens and retina of the eye as well as a uniform alignment of the photoreceptors in the retina. He also maintains the stable spherical shape of the eyeball. The regulation of the intraocular pressure is provided by the aqueous humor. It is formed from the epithelium of the ciliary body and passes between the iris and lens of the eye through the pupil into the anterior chamber of the eye. From there it flows out through the trabecular meshwork of the angle through Schlemm's canal into the episcleral venous system. The intraocular pressure thus results from the ratio of production to discharge flow of the aqueous humor.

Measurement

Normal intraocular pressure is about 10 to 21 mmHg. For its measurement, there are different methods that can be summed up under the term tonometry. Orienting Ophthalmologists examine the intraocular pressure manually by pressing lightly on the closed eye ( palpation ). Experienced investigators can estimate that the intraocular pressure within certain limits accuracy of about 2 mm Hg. Of apparatus, it is usually determined by a so called applanation Goldmann. The force is measured which is required for a defined mechanical flattening of the above drug- anesthetized cornea. Alternatively, a non-contact measurement by non-contact tonometry ( flattening of the cornea by an air shock ) are performed. Other methods are the Impressionstonometrie Dynamic Contour Tonometry and the. Although the applanation tonometry is currently the method of choice, but all measurement methods also have their drawbacks. Since the introkulare pressure can fluctuate throughout the day, several distributed over the day measurements indicated ( days pressure profile).

Costs

The measurement of intraocular pressure is as a precautionary measure controversial: While the Medical Service of the Central Federal Association of Health Insurance they " tend to be negative" considers to be the director of the University Eye Clinic of Mainz Norbert Pfeiffer holds " general screening [ for ] makes perfect sense. " Costs this will not, however, covered by statutory health insurance funds in Germany, so that it represents a individual health service ( IHS ). When the measurement is, however, medically necessary, for example after a glaucoma has been diagnosed or safe for long-term cortisone therapy, the cost is paid to the treatment package. The reason that the costs are not covered generally in the context of a glaucoma screening, the Federal Joint Committee is the " unknown reliability of the test in people without specific symptoms or risk factors " to.

Pathology

Flows from chamber less water than is produced, the intraocular pressure increases. A sustained rise above about 21 mmHg is not tolerated in the rule and can lead to damage of the optic nerve, for glaucoma ( glaucoma). Within certain limits, the individual eye, an increase of intraocular pressure without harm endure ( Tensionstoleranz ), but the higher the pressure increases, and the longer this situation lasts, the more likely it is to be expected damage. In contrast, the case of reduced Tensionstoleranz glaucoma occur without intraocular pressure rise ( normal tension glaucoma ). Although increased intraocular pressure is a very important, but not the only symptom of glaucoma dar. dignity exclusively an increase in pressure as a diagnostic criterion used, would be overlooked half of glaucoma.

The explicit study of the chamber angle is performed with a so-called contact glass and called gonioscopy.

There are a number of risk groups that are particularly vulnerable to a pathological increase in pressure. Another reason why it is generally recommended that a screening starting at age 40.

Treatment with an abnormal pressure increase

There are conservative and surgical options to treat elevated intraocular pressure with the aim to improve either the outflow of aqueous humor or get back to normal or decrease the production of aqueous humor. Drug therapy is carried with eye drops, so-called antiglaucoma through. In addition to the beta-blockers have long successfully adopted prostaglandins and alpha agonists are used for pressure reduction in the last years more and more. Also include carbonic anhydrase inhibitors to the active preparations.

Ophthalmic surgical processes come into question if drug therapy fails or alone does not lead to the goal of treatment. These are in addition to the conventional methods such as trabeculectomy or iridectomy a series of laser- surgical procedures such as argon laser trabeculoplasty, the ( ALT) or selective laser trabeculoplasty ( SLT).