The eye receives its nourishment from a clear fluid called “aqueous humor” that is produced behind the iris, flows through the pupil into the area between the iris and cornea. It then drains out of the eye into the blood circulation through a structure called the trabecular meshwork or drainage canal (also referred as the angle). The two most common forms of glaucoma are Open Angle Glaucoma and Narrow/Closed Angle Glaucoma.
In Open Angle Glaucoma, the drainage canal though open, gets clogged over time causing the aqueous humor to drain out of the eye too slowly. Most people with this type of Glaucoma have no symptoms and no warning signs. If not diagnosed and treated on time, gradual, permanent loss of vision can occur.
In Closed-angle glaucoma, the iris protrudes forward to narrow or block the drainage angle. As a result, aqueous can no longer reach the trabecular meshwork causing sudden increase in eye pressure. Symptoms of angle closure glaucoma include headaches, severe eye pain, nausea, blurring or loss of vision.
A form of open angle glaucoma is called Low Tension or Normal Pressure Glaucoma in which damage to the optic nerve occurs at normal eye pressure. People of Japanese ancestry, family history of normal tension glaucoma, heart disease or autoimmune disease are at a higher risk.
Some other types of Glaucoma include Pigmentary Glaucoma, Pseudoexfoliation Glaucoma, Glaucoma caused by cataract, diabetes, inflammation, trauma, tumors.
Risk factors for Glaucoma include:
- Family history
- Race, especially African Americans and Hispanic races
- Prolonged Steroid use
- Thin corneal thickness
The key to preventing serious vision loss or blindness from glaucoma is early detection and treatment.
Medications, most often eye drops, help control Glaucoma by reducing the eye pressure. Some drops work by reducing the amount of fluid being produced inside the eye while others work on increasing the amount of fluid getting out of the eye. Combination drugs are available for patients who require more than one type of medication. Although glaucoma drops are very effective, they have to used daily, often multiple times a day. Some patients develop side effects such as redness or irritation, dryness, itching. Any side effects experienced should be reported to your doctor. Depending on your general health and other medical conditions, however, you may be a poor candidate for glaucoma eye drops. This is because medications placed in the eye are absorbed into the conjunctival blood vessels on the eye’s surface. A certain percentage of the active ingredient of the medication, though small, will enter the bloodstream and may adversely affect functions such as heart rate and breathing.
If you use glaucoma drops, you know it’s all too easy to miss a dose. That can be a problem, because uncontrolled eye pressure spikes can further worsen the damage from Glaucoma and affect your vision. Fortunately, reminder apps are available for smartphones, iPads and iPod Touch.
Although there has been a lot of interest in Marijuana and its role in decreasing eye pressure, no research has found that marijuana is anywhere near as effective as legal glaucoma medications. Additionally, marijuana’s effect on eye pressure only lasts 3-4 hours, which means that in order to get sustained drop in eye pressure, it would have to be smoked 6-8 times a day. Furthermore, Marijuana lowers blood pressure, which can result in reduced blood supply to the optic nerve, which in turn might harm the optic nerve
The American Academy of Ophthalmology, American Glaucoma Society, among other authoritative sources, say that the risky side effects of marijuana (such as lowered blood pressure, increased heart rate, poor pregnancy outcomes, poor motor coordination, impaired memory and increased risk of cancer and emphysema) far outweigh any benefit.
SLT (selective Laser Trabeculoplasty) has become increasingly popular as an intermediate step between drugs and traditional surgery. This procedure takes between 10 and 15 minutes and is painless. The laser beam (a high energy light beam) is focused upon the eye’s drain. Contrary to what many people think, the laser does not bum a hole through the eye. Instead, the eye’s drainage system is changed in very subtle ways so that aqueous fluid is able to pass more easily out of the drain, thus lowering IOP.
You may go home and resume your normal activities following laser. After this procedure, many patients respond well enough to be able to avoid or delay surgery. While it may take a few weeks to see the full pressure-lowering effect of this procedure, during which time you may have to continue taking your medications, many patients are eventually able to discontinue some of their medications. This, however, is not true in all cases. Your doctor is the best judge of determining whether or not you will still need medication. Complications from laser are minimal, which is why this procedure has become increasingly popular and is some times recommended before eye drops in some patients. It is especially a great first option in people who find it difficult to comply with the strict, regular schedule needed for administering eye drops or find it difficult to instill drops in their eyes due to tremors or arthritis.
This procedure is used to make an opening through the iris, allowing aqueous fluid to flow from behind the iris directly to the anterior chamber of the eye. This allows the fluid to bypass its normal route. LPI is the preferred method for managing a wide variety of angle-closure glaucomas.
Two laser procedures for open-angle glaucoma involve reducing the amount of aqueous humor in the eye by shrinking part of the ciliary body, which produces the fluid. These treatments are usually reserved for use in eyes that either have elevated eye pressure after having failed other more traditional treatments, including filtering surgery, or those in which filtering surgery is not possible or advisable due to the shape or other features of the eye. Transscleral cyclophotocoagulation uses a laser to direct energy through the outer sclera of the eye to reach and shrink portions of the ciliary body, without causing damage to the overlying tissues. With endoscopic cyclophotocoagulation (ECP), the instrument is placed inside the eye through a surgical incision, so that the laser energy is applied directly to the ciliary body tissue.
When medications and laser therapies do not adequately lower eye pressure, surgical treatment may be needed to control the eye pressure. The most common of these operations is called a Trabeculectomy, which is used in both open-angle and closed-angle glaucomas. In this procedure, the surgeon creates a tiny passageway from the inside to the outside of the eye to drain the fluid into a cyst or bleb under the upper eye lid. The surgically created drainage hole can close with time and the eye pressure can rise again. This happens because the body tries to heal the new opening, as if it was an injury. Many surgeons perform trabeculectomy with an anti-fibrotic agent that is placed on the eye during surgery and reduces such scarring during the healing period. The most common anti-fibrotic agents are Mitomycin-C and 5-Fluorouracil.
About 50 percent of patients no longer require glaucoma medications after surgery for a significant length of time. A trabeculectomy is usually an outpatient procedure. The number of post-operative visits to the doctor varies, and some activities, such as driving, reading, bending and heavy lifting must be limited for two to four weeks after surgery.
Drainage Implant Surgery
Several different microscopic devices have been developed to aid the drainage of aqueous humor out of the anterior chamber and lower the eye pressure All of these drainage devices share a similar design which consists of a small silicone tube that extends inside the eye. The tube is connected to one or more plates, which are sutured to the surface of the eye, usually not visible. Fluid is collected on the plate and then absorbed by the tissues in the eye. This type of surgery is thought to lower the eye pressure less than trabeculectomy but is preferred in patients whose pressure cannot be controlled with traditional surgery or who have previous scarring.
New technologies and devices, known as MIGS, aim to lower the eye pressure in a much safer manner with rapid recovery and minimal restrictions. Instead of creating an artificial drain in the eye, they unclog the natural drainage system of the eye and enhance drainage. The latest MIGS approaches include the iStent, Trabectome, Viscocanaloplasty. Currently, MIGS approaches and techniques are best-suited to glaucoma patients with early to moderate disease, preferably in combination with cataract surgery.
There are several advantages offered by the MIGS procedures. These are bleb-independent procedures that avoid the major complications of traditional surgery, such as life time risk of infection with subsequent loss of vision or loss of eye, long term risk of leaks and too low eye pressure.
Additionally, they are usually performed at the time of cataract surgery with similar recovery, postoperative drop regimen and restrictions of activity as cataract surgery alone. A large majority of patients can not only achieve independence from eye glasses but minimize or eliminate glaucoma eye drops.
While there is no cure for Glaucoma just yet, it can be controlled and stabilized by maintaining the eye pressure in a safe range. Contrary to previous belief, there is no magic or miracle cutoff value for safe eye pressure. Instead, it is an individualized number or range, which depends on the severity of glaucoma damage, age, corneal thickness, besides a host of other factors. All current treatments in Glaucoma are directed towards lowering the eye pressure. It is important to maintain a regular schedule of eye pressure checks, dilated exams of the optic nerve and visual field testing, to diagnose and treat subtle worsening of glaucoma damage.