What is glaucoma ?
Glaucoma is a disease caused by increased pressure within the eye destroying optic nerve fibres, which results in damage to the optic nerve. This nerve carries images to the brain and as the fibres of this nerve are damaged blind spots can appear in the field of vision and the visual field gradually narrows. If the entire nerve is damaged, blindness results. In the initial phase of the disease the patient generally does not have any symptoms. The optic nerve is damaged over a long period and by the time the patient is aware of the disease the damage may be irreparable.
Is every increase in intraocular pressure glaucoma?
Intraocular pressure is an important risk factor for glaucoma but it is not the only decisive factor. If there is no damage to the optic nerve, and there is no loss of visual field, this means glaucoma has not yet developed and there is only ocular hypertension (higher than normal intraocular pressure in the absence of optic nerve damage). This situation can only be understood through further investigations.
Can people with low or normal eye pressure have glaucoma ?
Yes this is possible, it is known as normotensive glaucoma (normal-pressure glaucoma). Intraocular pressure may be tested at normal or slightly lower than normal levels, but considering factors such as the individual’s own eye structure, sensitivity of nerve fibres and fineness of the cornea this pressure may be relatively high for that person. In other words, each person has a unique threshold for eye pressure and this is slightly different for everyone. High eye pressure for one person may be considered normal for someone else. However, intraocular pressure of 10-20 mmHg is considered to be normal. Values of 20 mmHg and above are considered to be indications of glaucoma.
Who develops glaucoma?
People over the age of 40 have an increased risk of glaucoma. The risk of developing glaucoma is higher in people with a family history of glaucoma. Circumstances such as diabetes, eye injury, eye inflammations like uveitis or iritis, high myopia, hyperopia and long-term use of corticosteroids can all increase the risk of developing glaucoma.
Why does glaucoma occur?
Intraocular fluid (aqueous humor) which is needed as nutrition for the eye, is normally secreted inside the eye on a regular basis (this fluid has nothing to do with the tears on the outer surface of the eye). While intraocular fluid is produced at a constant speed, the same amount of fluid leaves the eye. There is a balance between the amount secreted and the amount that leaves via discharge channels (the trabecular meshwork). Glaucoma occurs when these discharge channels become completely or partially blocked and the secreted intraocular fluid cannot leave the eye at the same rate as it enters, thus the pressure inside the eye rises. This rising intraocular pressure then causes damage to the optic nerve cells.
Only in the late stages of glaucoma, with irreversible loss of vision, some patients experience symptoms such as, headaches appearing in the morning, light rings seen around lights at night, occasional blurred vision and pain around the eyes.
What are the diagnostic tests for glaucoma?
High intraocular pressure in a patient is not suffiecient evidence to be able to make a diagnosis of glaucoma. To confirm the diagnosis of each patient with suspected glaucoma the following tests are required:
1. Nerve fiber layer thickness (oct)
2.Corneal thickness (pachymetry)
3. Visual field (bga)
a definitive diagnosis can be made based on the evaluation of these tests. In addition, these tests should be repeated at regular intervals to monitor any changes in the patient.
Treatment of glaucoma:
It must be remembered that nerve fiber damage caused by glaucoma is irreversible. Eye drops, laser surgery and surgical operations are used only to prevent further damage.
Eye pressure medication either decreases the production of intraocular fluid secreted into the eye or facilitates the outward flow. These drugs should be taken regularly every day and are life-long. For patients who, despite the use of medication, there is no decrease in intraocular pressure and the visual field is narrowing, or for patients who do not wish to take medication or cannot take medication, then laser treatment can be discussed.
Selective Laser Trabeculoplasty (SLT)
Laser treatment can be applied to the discharge channels to facilitate the fluid to leave the eye more freely. The process is extremely simple and risk-free. It should not take more than 5 minutes. The process does require an operating theatre, instead it can be carried out in an examination room with the patient in a sitting position. This process opens the discharge channels and the intraocular fluid starts to flow freely. The process may need to be repeated every 1-2 years if the problem begins to return.
The most frequently used method to facilitate the discharge of intraocular fluid is to create a new channel (trabeculectomy ). The operation does not require hospitalisation and can easily be performed under local anesthesia.