The Pathology of Glaucoma Induced Blindness
Glaucoma is a fairly prevalent disease, affection roughly 2% of adults over the age of 40, in the United States.
How does glaucoma affect vision ?
Glaucoma is defined as a family of diseases that affects the optic nerve. This most often happens when the pressure inside the eye is too high leading to damage to the optic nerve, which is responsible for sending visual signals from the eye to the brain for processing.
Glaucoma was long thought to be a pressure disease only. We now know what we don’t know and while scientists don’t fully understand all the pathophysiology or mechanisms leading to optic nerve damage, a few disease mechanisms have been proposed including mainly the mechanical effect of eye pressure and the theory of vascular component.
While we don’t fully understand glaucoma pathology, we know some of the risk factors associated with glaucoma. Some of them include, eye pressure, age, family history, use of certain medicines, ethnic background.
There are two main types of glaucoma:
Primary Open Angle Glaucoma (POAG) is the most prevalent. Damage to the optic nerve happens slowly, insidiously, and at first patients do not experience any symptoms. It can takes years for the disease to progress.
Acute Angle Closure Glaucoma happens usually for anatomical reasons. The drainage system of the eye because blocked, leading to sudden, drastic increase in eye pressure leading to a constellation of symptoms.
In the case of primary open angle glaucoma, the onset of damage to the optic nerve is usually slow. With the right drugs, laser or surgical procedures, this optic nerve disease can be stopped or at least slowed down.
Since most cases of glaucoma are insidious in nature, it is paramount that patients get checked periodically by an optometrist or ophthalmologist. A pressure check is not enough since some patients with glaucoma do not have elevated eye pressure. Conversely, some patients with elevated eye pressure do not have glaucoma. Since glaucoma is a disease of the optic nerve, a direct observation of the nerve must be made by the clinician to assess its health.
This is best done by observation in the doctors office during fundus examination through a dilated pupil. For those populations outside the US without access to eye doctors, a fundus photo can give some information.
Very often, even in the context of a well performed eye exam by a trained eye doctor, the diagnosis is not clear cut. Many patients belong to a group called “ glaucoma suspect”. Those patients exhibit some characteristics of the disease in the setting of positive risk factors.
Those patients need to be monitored very closely to assess changes over time and true conversion to glaucomatous disease.
As we said prior, the pathology of glaucoma is not well understood. What we do know is that modifying the intra ocular pressure (IOP) generally has an impact on the disease. This is why the eye pressure in the main target of most open angle glaucoma treatment.
We recommend patients to see an eye doctor regularly to check for glaucoma, because glaucoma left undetected and untreated leads to permanent vision loss and unfortunately sometimes to blindness.