Glaucoma is a disease that affects the optic nerve which is responsible for our vision. The optic nerve receives light signals from the retina and serves as a cable that transmits these impulses to the brain which we perceive as vision. The optic nerve damage generally starts to cause mild loss of side vision that progress to loss of central vision and blindness if left undiagnosed and untreated.
|Normal Visual Field||Side Vision Defect|
The optic nerve damage is usually, but not always, caused by an elevated eye pressure. In some cases, glaucoma can occur even if the eye pressure is within normal. This form of glaucoma is brought about by poor regulation of blood flow to the optic nerve.
The eye pressure is due to the presence of a clear fluid in the anterior chamber which is the space in the front of the eye. This fluid is called the aqueous humor and is responsible for the nourishment of the surrounding tissues. The fluid leaves the chamber through a drain known as the trabecular meshwork at an angle where the cornea and iris meet. The aqueous humor should not be confused with the tears which are produced by the lacrimal gland outside of the eye.
There are two main types of glaucoma: open angle glaucoma and closed angle glaucoma. In open angle glaucoma, the structures of the eye appear normal, but the fluid in the eye does not flow properly through the drain. The fluid exits the eye slowly; therefore the fluid builds up and elevates the pressure inside the eye which damages the optic nerve. That is why controlling the pressure inside the eye is important.
In some people, the anterior chamber angle can be narrow or closed. People with small eyes, like those who are of Asian descent or who are farsighted are at risk of developing closed angle glaucoma. In this condition, the eye pressure can go up very suddenly.
For most people, glaucoma, especially the open angle type, produces no pain and no accompanying symptoms until noticeable loss of vision occurs late in the disease, hence it is called the “silent thief of sight”. On the other hand, closed angle glaucoma can raise the eye pressure to severe levels in a very short time accompanied by sudden severe eye pain, headache, a red eye, nausea and vomiting, blurred vision and seeing colored haloes around lights. If any of the mentioned symptoms are experienced, seek immediate medical care.
Through a thorough painless eye examination in your eye doctor’s clinic, individuals at risk for glaucoma can be screened and detected before nerve damage occurs. The eye pressure can be measured. The anterior chamber angle and the optic nerve can be visualized. Sophisticated tests can also be used for diagnosis like the optical coherence tomography, visual field testing and pachymetry. These tests are requested repeatedly to assess the efficacy of the treatment and detection of any disease progression which can affect the course of management.
Glaucoma is a progressive disease but if diagnosed and treated early, it can be controlled. Most patients are started on eye drops to decrease the eye pressure to acceptable and safe levels. Laser therapy may be needed in some forms of glaucoma. If however, both medical and laser treatments fail to control the disease, surgical therapy may be necessary. Patients with glaucoma need to be aware that it is a lifelong disease causing irreversible optic nerve damage and visual loss. Therefore strict compliance to the treatment regimen and scheduled visits is important.