Glaucoma is a neuropathy – an eye condition that damages the optic nerve, accompanied by high intraocular pressure, changes in the visual field, and gradual loss of vision.
High intraocular pressure is caused by increased production or harder flowing out of the aqueous humor from the eye. The built-up aqueous humor creates pressure on the optic nerve fibers that get easily damaged.
In the beginning, the changes in the visual field are unnoticeable and completely gradual. However, over time specific incidents happen that can lead to complete loss of vision if the condition isn’t treated. In the beginning, central vision isn’t impaired, so patients don’t feel any symptoms for a long time. This is why glaucoma is said to be an insidious disease.
The Types of Glaucoma
The most often type of glaucoma is open-angle glaucoma. This condition doesn’t have any symptoms. People over the age of 60 are at a high risk of suffering from the disease, as well as people with myopia, diabetics, and patients whose parents had glaucoma.
5% of patients develop glaucoma as a result of the blocked chamber angle, so the aqueous humor cannot flow out of the eye. The chamber angle can get blocked due to eye inflammation, an injury, or a congenital anomaly of the eye channel. This is a condition called closed-angle glaucoma. The angle can also get blocked as a result of some medication for cycloplegia, during eye examination or anesthesia, as well as during a longer stay in a half-lit room or a cinema auditorium. In case the angle is closed quickly, dramatic symptoms may occur: eye pain, nausea, vomiting, halos around the sources of light, blurred vision. Acute closed-angle glaucoma is an urgent condition, it requires a doctor’s examination and adequate medicament and laser therapy.
There is also a type of glaucoma called normotensive glaucoma or normal-pressure glaucoma. It arises as a consequence of weakened peripheral circulation or flow through the optic nerve. With this type of glaucoma, changes in the optic nerve occur although the intraocular pressure is within normal values.
Determining the Diagnosis
To determine the diagnosis, the doctor has to check visual acuity, ocular pressure, chamber angle, pachymetry (measuring the thickness of the eye’s cornea), and the functional state of the optic nerve with special tests: computerized visual field and OCT (optical coherence tomography). It is also important to do a screening of the optic nerve papilla for more reliable and objective monitoring.
Ocular pressure is most reliably measured with the applanation method, i.e. flattening the cornea on a biomicroscope after cycloplegia with eye drops. There are also other less precise methods. Normal-pressure values range between 10-22 mmHg, whereas normal daily variations are about 3 mmHg. During the determination of the diagnosis, the pressure should be measured at different time intervals throughout the day. Therefore, it is best to do a diurnal cycle – daily curvature of ocular pressure.
The visual field is important to mark potential defects at the beginning of the condition. It is repeated 1-2 times a year to determine if the condition has progressed. This examination requires concentration and it is not always easy to do.
The examination of the chamber angle is executed with a special loop (lens) placed onto the eye after cycloplegia with eye drops.
OCTA technique to screen the eye is a newer, non-invasive diagnostic method that registers movable contrast images of microcirculation. With this analysis, the doctor can check the density, placement, and symmetry of the capillary network in the optic disc. Patients with damage to the optic nerve have a condition where nerve fibers thin, degeneration of ganglion cells, reduced vascular network, or zones without vascular flow. High resolution of the screening enables us to identify in detail the earlier inaccessible elements of the eye, such as the dense vascular network around the optic disc. This way changes on the optic nerve can be registered even several years before there are changes in the visual field. This type of screening is very important when there is a condition called ocular hypertension. Such patients have pressure values above the normal limits but they don’t have any symptoms of the condition.
Treatment
Glaucoma is a condition that cannot be cured and that does not have any symptoms. After the age of 40, it is advisable to do an eye examination once a year. If the condition is diagnosed on time, the doctor needs to determine a suitable therapy adequate for the patient based on all the analyses. With this, it is possible to stop the progression of the condition and “preserve” the current state. Regular checks are also necessary.
The treatment is done in local therapy with eye drops. Sometimes it is necessary to apply a combination of a few types of drops put at a certain time according to a doctor’s prescription.
In case the medication therapy doesn’t help, in some special cases, it is necessary to do a laser intervention or surgery.