In glaucoma, there is an imbalance between eye pressure (intraocular pressure) and blood flow to the optic nerve. As a result, the optic nerve fibers slowly perish without being noticed. By reducing eye pressure, this process can be stopped but not reversed.
The aqueous humor is formed by the ciliary body on the back of the iris and flows past the natural lens through the pupil into the anterior chamber. There, it flows off in the chamber angle between the iris and cornea and returns to the bloodstream via small veins.
In the most common types of glaucoma, this outflow is reduced, which can have various causes. The aqueous humor is backed up and the intraocular pressure increases. This ultimately impairs blood flow to the nerve fibers in the area of the optic nerve
If left untreated, glaucoma first leads to visual field loss, then to complete blindness.
The earlier glaucoma is diagnosed, the better permanent damage can be averted and the better the prognosis. Age and family burden are the main risk factors. First-degree relatives (parents or siblings) of people with glaucoma should have at least every three, from 55 every two and over 65 years. Depending on the individual risk situation and the severity of glaucoma, closer controls may also be necessary.
During routine examinations (screening), so-called biomicroscopy and eye pressure measurement are sufficient to detect the first signs of glaucoma. These tests are part of a general ophthalmological examination. In biomicroscopy, the ophthalmologist uses a microscope to look through a lens into the interior of the eye and assesses the retina, vessels and optic nerve for abnormalities. Before eye pressure is measured, the surface of the eye is made insensitive with an anesthetic drop. A so-called tonometer measures intraocular pressure via a small glass cylinder by touching the cornea.
To avoid injuries to the cornea, the eyes should not be rubbed after the measurement.
As soon as the optic nerve is noticeably hollowed out (excavated) or the eye pressure is above the normal range (11 to 21 mmHg), more complex examination methods are indicated:
With high-precision laser beams, the nerve fibers in the area of the optic nerve are scanned and displayed graphically on the screen. In the very first so-called baseline measurement, the thickness of the optic nerve fibers is compared with the “normal population.”
At the bottom left of the image, the fiber thicknesses at the respective location of the optic nerve are compared with the normal population. Green means that the values comply with the norm, yellow is below average.
Red is most likely to already have a glaucoma-specific defect. Since the optic nerves that have died cannot be repaired, it is all the more important to recognize the progress of a defect at an early stage. For this purpose, the OCT measurements are repeated and compared with each other every three to six months. If there is a decrease in nerve fiber layer thickness over several measurements, it can be assumed that glaucoma exists and eye pressure should be reduced with medication or with a laser.
While eye pressure measurement falsely results in lower values for thin corneas, eye pressure is more likely to be higher than they actually would be. By means of precise corneal thickness measurement and nomogram, the true internal pressure of the eye can be estimated and thus the risk of progressive glaucoma disease can be assessed.
Damage to the fibers of the optic nerve (e.g. due to glaucoma) leads to visual field defects over a certain extent. Functional glaucoma damage can therefore be visualized by examining the visual field. Especially in advanced stages, visual field tests are necessary to detect further progression of glaucoma.
The patient sits in a darkened room and looks at a central fixation point in a large white hemisphere. In different chronological sequences, further points are displayed at various points in the hemisphere. Without looking away from the fixing point, the patient should immediately press a button to make known that he was able to perceive the point. This creates a map that reflects the patient's field of vision.
The two circles represent the field of vision of the left eye (left) and the right eye (right). Dark areas correspond to visual field failures, i.e. the patient sees nothing there. In contrast to pachymetry and OCT measurement, visual field examination is a subjective measurement, in which the patient's attention and practice also play a role.
Abnormal eye pressure and/or initial abnormalities in the optic nerve are usually detected at the onset of the disease. Measurements are carried out again within three to six months and compared with the first values. As soon as there is evidence of a worsening of glaucoma progression and the first steps of treatment are discussed with the ophthalmologist:
If conservative eye pressure lowering methods are not sufficient to stop the progression of glaucoma, surgical procedures are indicated:
