Glaucoma is an eye disease and a leading cause of blindness in the United States. Tragically, this loss of vision could have been prevented in many individuals with early detection and treatment.
Glaucoma is more precisely a disease of the optic nerve. The optic nerve is like the cable on your cable TV. his nerve carries the images that we see from the retina to the brain. The optic nerve is like a cable in that it is made up of many (about 1 million per nerve) smaller nerve fibers and when these optic nerve fibers get damaged, blind spots in your vision develop. These blind spots usually go undetected until advanced damage occurs to the nerve. If a significant amount of the nerve is destroyed, blindness can occur.
Again, early detection and treatment is the key to preventing optic nerve damage and blindness from glaucoma. Your doctor can often detect glaucoma during your comprehensive eye examination. In other cases, more in-office testing is required to make the diagnosis.
The clear fluid that circulates in the front of the eye is called the aqueous humor. (This fluid is not the same as tears). To maintain a healthy level of pressure within the eye, a small amount of this fluid is being produced constantly while an equal amount flows out of the eye through a microscopic drainage system.
Most experts feel that glaucomatous nerve damage is related to an elevated pressure in the eye. The assumption is that higher pressures cause nerve damage and therefore blindness.
The pressure rises because the flow of aqueous fluid out of the eye through the drainage system does not keep up with the production of this fluid inside the eye. Since the eye is a closed system if more aqueous is put in than is removed, the pressure will rise. This elevated pressure is thought to be at least in part why the optic nerve is damaged.
Yes, glaucoma is actually a group of diseases. It is useful to determine what type of glaucoma a patient has because the initial treatment may differ. The main way that glaucomas are defined is by fluid access to the drainage system inside the eye. These drainage canals are located at approximately the junction of the cornea and iris. This area is called the anterior chamber angle.
If the angle is open, i.e. fluid has access to the drains, it is called open angle glaucoma. If the fluid has limited access to the drains, it is called narrow or closed angle glaucoma.
Glaucomas are also divided into primary and secondary types. Secondary means that other event or disease caused glaucoma as a complication. For example, many people develop glaucoma after an eye injury. This “traumatic glaucoma” is a type of secondary glaucoma.
1. Chronic open angle glaucoma
Also knows as primary open angle glaucoma and is the most common form of glaucoma in the United States. The risk of developing chronic open-angle glaucoma increases with age. The aqueous fluid has access to the drains, but these drains become less efficient over time, and pressure within the eye gradually increases, which can damage the optic nerve.
Typically, open-angle glaucoma has no symptoms in its early stages, and vision remains normal. As the optic nerve becomes more damaged, blank spots begin to appear in your field of vision. You typically won’t notice these blank spots in your day-to-day activities until the optic nerve is significantly damaged and these spots become large. Ultimately, if enough fibers are damaged, blindness can result.
2. Closed angle glaucoma.
Also known as narrow or acute angle glaucoma and in contrast to open angle glaucomas, the fluid cannot effectively get to the drainage system. This is because some eyes are formed with the iris too close to the drainage angle. In these eyes, which are often small and farsighted, the drainage angle can be obstructed by the iris. Since the fluid cannot exit the eye, pressure inside the eye builds rapidly and causes an acute closed-angle attack. This can lead to blindness in some cases within hours.
Unfortunately, two-thirds of those with closed angle glaucoma develop it slowly without any symptoms prior to an attack. This makes regular visits to your doctor very important.
Your doctor will consider many kinds of information to determine your risk for developing glaucoma. Some important risk factors include advanced age, increased pressure and thin central corneal thickness both of which can be measured during your eye examination. Other factors include family history of glaucoma, ethnic background and concurrent systemic diseases, such as diabetes and migraine headaches to name a few.
Your ophthalmologist will consider all of your risk factors. In addition, during your eye exam the pressure is routinely measured and your optic nerve is evaluated to see if it shows signs of damage. If any suspicion exists additional tests can be done in our office.
These include:
· Corneal Pachymetry – measures the central corneal thickness
· Gonioscopy – evaluates the anterior chamber angle to see if it is open, closed or damaged
· Perimetry – measures the visual field for subtle, early vision loss that is often unnoticed by the patient
· Nerve Imaging – photographs or other computer imaging of the nerve can be done to help in the diagnosis.
As a rule, damage caused by glaucoma cannot be reversed. Eye drops, laser surgery in the office, and conventional surgery in the operating room are used to help treat glaucoma and therefore, prevent further damage. In some cases, oral medications may also be prescribed.
With any type of glaucoma, periodic examinations are very important to prevent vision loss. Because glaucoma can progress without your knowledge, adjustments to your treatment may be necessary from time to time.
The bottom line is that regular eye exams and consultation with our doctors can help to prevent unnecessary vision loss.