What is glaucoma?
Glaucoma is a serious eye disease and one of the leading causes of blindness in the world today. In glaucoma, the loss of vision is due to destruction of the optic nerve, a structure located in the fundus of the eye that conducts images to the brain. The optic nerve can be likened to an electrical cord made up of numerous wires – the nerve fibers. In glaucoma, these fibers are destroyed, so that images can no longer be carried to the brain. Dark spots appear in the field of vision and as the disease progresses, there is progressive loss of vision. Therefore early diagnosis and treatment are essential.
What are the symptoms of glaucoma?
In general, the patient with glaucoma only realizes that he has a problem at an advanced stage of the disease, when dark patches begin to appear at the periphery of the field of vision. As the disease progresses the spots increase, resulting in gradual loss of vision.
Why does eye strain increase?
In glaucoma there is increased pressure inside the eye – eye strain. In general, eye strain greater than 22 mm/Hg can cause destruction of the optic nerve fibers.
Why does eye strain increase? Eye strain increases because the fluid that circulates inside the eye – the aqueous humor – accumulates inside the eye. In a normal eye, the aqueous humor is continuously produced within the eye, and also continuously flows through its own outlet channels. When these channels cease to function efficiently, or become blocked, there is a build-up of fluid inside the eye. This excessive pressure compresses the optic nerve and can lead to its destruction.
Loss of vision in glaucoma may also occur in situations of normal ocular tension, and it is very likely that there are other factors that cause destruction of the optic nerve, such as blood circulatory problems in the optic nerve.
Although the causes of glaucoma are not yet known, the following are considered to be risk factors:
- Age over 35 years
- Family history of glaucoma (individuals with more cases of glaucoma in the family)
- Medication (e.g. prolonged corticosteroid treatment)
- Diseases (e.g. hypertension, diabetes)
- Black or Asian ethnicity
What types of glaucoma are there?
Open-angle glaucoma is the most common form of glaucoma (about 90% of cases) and is usually associated with aging. In open-angle glaucoma there is an increase in ocular tension due to difficulties in the flow of the aqueous humor. In these cases the destruction of the optic nerve is slow and painless, and the patient may only discover that he has glaucoma when the lesion is already very extensive.
Closed-angle glaucoma is an acute, rare, and serious condition that requires emergency treatment. In this type of glaucoma, the iris completely blocks the outflow channels of the intraocular fluid, causing a sudden increase in eye strain and severe eye pain, blurred vision and colored halos around lights, headache, nausea and vomiting. There are also rare cases of congenital glaucoma, mainly affecting babies, which is corrected through surgery, and secondary glaucomas associated with diseases (such as diabetes or inflammation), or resulting from treatment with certain drugs (e.g. steroids).
How is glaucoma diagnosed?
Glaucoma is best detected through regular check-ups with an ophthalmologist. During the check-up, the doctor will perform a detailed examination, which includes:
- Medication for ocular hypertension (tonometry)
- Evaluation of the aqueous humor pathways (gonioscopy)
- Evaluation of possible destruction of the optic nerve (ophthalmoscopy)
- Evaluation of the visual field in each eye (perimetry)
Depending on the patient’s situation, the ophthalmologist will decide which tests to perform and how often these tests should be repeated.
What is the treatment for glaucoma?
Treatment of glaucoma is aimed at avoiding increased lesion and loss of vision, since the destroyed optic nerve cannot be recovered! The following treatments are available for glaucoma:
Medication: Antiglaucomatous (eye drops or tablets) to reduce eye strain, reduce the production of aqueous humor in the eye, or facilitate its flow. In some cases the medication can produce side effects, which should be reported to the doctor:
– Eye drops: red eye, blurred vision, dry eye, headache or heart and respiratory changes.
– Tablets: fatigue, tingling in the fingers and toes, drowsiness, loss of appetite, gastrointestinal problems. To have the desired effect, these drugs must be applied regularly, possibly for the rest of the patient’s life. Therefore, it is essential that the patient adheres to the therapy recommended by the doctor.
Laser Treatment: Laser surgery is usually used when medication cannot control the eye strain. Laser is used to unblock the channels through which intraocular fluid flows, in the case of open-angle glaucoma – trabeculoplasty, or to open communications at the base of the iris in the case of closed-angle glaucoma – iridotomy.
Surgery: In general, surgery is reserved for cases where the patient’s condition cannot be controlled by medication and laser treatment. In these cases, the ophthalmologist also opens channels for the flow of intraocular fluid, to reduce ocular tension and control the disease progression.