What is Glaucoma?
Glaucoma is an eye disease that damages the optic nerve. The optic nerve can be weak by the way it was made originally and then normal eye pressure damages it by pushing on it, or the nerve can be of normal construction and the pressure itself be too high and cause damage to it. Either way, the optic nerve is the site of damage with glaucoma.
Glaucoma is treated by lowering the pressure of the eye. This is the way the nerve is protected against further damage. It is important to know that the damage glaucoma does is not repairable. Because of that, it is important to detect glaucoma before damage occurs. Further, the changes in vision from glaucoma are not that of blurred vision. Instead, glaucoma gradually and painlessly narrows the peripheral (side) vision, eventually creating tunnel-vision. A person may read the eye chart perfectly with glaucoma, but their side vision is lost. Regular eye examinations and pressure checks are the only way to monitor for glaucoma and avoid loss if it begins.
How Is Glaucoma Detected?
Glaucoma is detected by using several tests. The first of these is the pressure check performed during a typical Comprehensive Eye Exam. The second is a careful examination of the nerve, again preformed after dilation of the pupils during a typical Complete Eye Exam.
If there is a suspicion of glaucoma or a high pressure detected during an eye exam, the doctor may suggest one or more of several tests that confirm whether there truly is glaucoma. The first of these is a visual field test. The test presents many lights to the patients in many areas of the side vision. The patient pushes a button if they see the lights. A compute randomly presents the lights to be seen, monitors the patients responses, and a printout of the results is created. If certain patterns emerge, glaucoma is said to be present. This test takes about 10-20 minutes to perform.
The second common test is an Ocular Coherence Tomography (OCT) of the retina or optic nerve. This test scans for thinning of the nerve or nerve layer that occurs when glaucoma is present. It is a straightforward test to have done, somewhat like having your picture taken while looking at a target the machine presents. This test takes about 1 minute to perform.
The third test is newer and is called an Electroretinogram (ERG). This test places stickers containing electrodes on the forehead and back of the head and measures the conduction through the optic nerve of each eye as the person stares at a shifting pattern. The conduction through a nerve is decreased if the pressure of the eye is too high. This test has the advantage of showing abnormal results before damage has occurred, making it possible to stay ahead of glaucoma in many cases.
Types of Glaucoma
There are two main forms of glaucoma, the more common is "open angle glaucoma" wherein the area that allows release of fluid is open but not functioning well, and there is also a form of glaucoma termed "narrow angle glaucoma." This differs from open angle glaucoma in the way it is detected and the way it is monitored and treated. The area of the eye that is narrow in narrow angle glaucoma is in the front chamber of the eye. A narrowing of the area where pressure is released occurs due to the way some people's eyes are put together or from changes that occur during aging. The narrowness is detected during a typical eye exam prior to dilation and is confirmed by directly visualizing the area by using a special lens called a gonioprism. Treatment for open angle and narrow angle glaucoma differ as noted below.
How Is Glaucoma Treated?
The mainstay of treating many cases of glaucoma is through the use of drops, or in a few cases, pills. Medications used in the treatment of glaucoma either lower the production of pressure or they let pressure more easily escape the eye. Many drops produce little to no side effects, but side effects or allergy are more possible with others. Your doctor will watch for side effects, but you should always report any suspicious changes to your health or eyes when trying any new medication. The biggest risk in using drops or pills are the chances of missing doses and allowing pressure to be inconsistently controlled. As well, the cost of medications in recent years has been a difficult factor for more people to afford ongoing medications.
Laser surgery has become increasingly safe and popular as a means to control pressure.
Laser treatment for classic "open angle" glaucoma
Carrying very, very little risk, Selective Laser Trabeculoplasty (SLT) is a procedure that takes just a few minutes to perform and reduces or eliminates a patient's need for drops by treating the area of the eye that allows the release of pressure. By cleaning up the area and not significantly changing the structure in the part of the eye treated, SLT can be used initially and even be used repeatedly to further lower pressure as time goes on. Many people choose to have SLT in that it is very safe and carries about a 90% chance of working to lower pressure or lessen drop requirements, thus saving money for the patient and insurances. Further, it is a consistent method of lowering pressure as compared to using drops which may be missed occasionally.
Laser treatment for "narrow angle" glaucoma
When the area where pressure typically escapes the eye is narrowed, as mentioned above, a laser procedure, termed a Peripheral Iridotomy (PI), is used to make a small opening in the iris (colored portion of the eye), allowing fluid to flow from behind the iris directly to the front chamber of the eye. This allows the fluid to bypass its normal route, thus widening the narrow angle and preventing angle-closure glaucoma pressure elevations.
When medications do not achieve the desired results, or have intolerable side effects, or when laser treatments are ineffective, your ophthalmologist may suggest surgery. Surgery can include one of many 'minimally invasive glaucoma surgery" ("MIGS") which are procedures that can help pressure escape the eye. These procedures are usually performed when cataract surgery is performed and can be understood to create a bypass for pressure around structures that do not allow its easy release. Two such common MIGS procedures are the iStent Implant and Goniotomy. These are illustrated below. MIGS are not commonly used as first line treatment for early glaucoma but bridge the gap between laser treatment and classical surgery.
Beyond MIGS devices, classical surgery or more significant implant devices can be performed that allow pressure to more easily escape the eye. These procedures are usually left in the hands of glaucoma specialists but are very successful. Fortunately, with early detection and appropriate monitoring and management by our physicians, the percentage of people who need such surgery for glaucoma is very small.
The mainstays of successful glaucoma treatment are regular visits and yearly testing of your eyes. Stay in communication with your doctor to stay ahead of the disease and most all cases of glaucoma go well nowadays. A disease that used to be a difficult experience may be successfully treated and not an imposition on life as it used to be just a short time ago. Good results are the general rule with glaucoma treatment today.