Alpha agonists have a dual mechanism of action within the eye. First, they decrease the production of fluid inside the eye, and second, they work to improve the drainage of fluid to the eye’s collector channels.
Side effects can include burning or stinging upon instillation of the eye drop, fatigue, headache, drowsiness, dry mouth, and dry nose. The most common side effect is an allergy, which occurs in 15-20% of patients. If you experience severe redness to the eyes or eyelids, stop the medication and call our office.
Beta-blockers work by decreasing the production of fluid that is made inside the eye. They used to be first-line therapy for glaucoma, but better medications have been developed. Therefore, Beta-blockers are mostly used as adjunctive therapy. One major benefit of these medications is that they are quite inexpensive since they have been generic for many years.
There are a number of systemic side effects that may be related to Beta-blocker use. They include low blood pressure, reduced pulse rate, fatigue, and shortness of breath in patients who have a history of asthma or other respiratory disorders.
Additionally, Beta-blockers can change cardiac activity by decreasing the amount of blood the heart pumps out, which may reduce the pulse rate and/or slow down the heart’s response rate during exercise. Rare side effects include reduced libido, hair loss, and depression.
Today, prostaglandin analogs are the gold standard medical therapy for glaucoma. They are known for superb results in lowering IOP, and for maintaining a low IOP throughout the day. This class of medication works by improving the outflow of fluid from the eye by enhancing uveoscleral outflow. One major advantage of these medications is that they have few systemic side effects.
The prostaglandin analogs have two very interesting side effects. First, they may change the iris color by increasing the amount of brown pigment inside the eye. Second, they are known for causing eyelashes to grow. Other side effects can include stinging, blurred vision, eye redness, itching, burning, and periorbital fat atrophy.
Carbonic anhydrase inhibitors (CAIs) lower IOP by decreasing the production of fluid that is made inside the eye. In many instances, CAIs are great adjuncts to the prostaglandin analogs. They come in two forms:
Drops = Azopt or Trusopt
Pills = Diamox or Neptazane
Side effects of the pill form of CAIs are numerous and are the reason why Diamox and Neptazane are not long-term glaucoma therapies. The side effects include tingling or numbness of the hands and feet, feeling weak or tired, upset stomach, memory problems, depression, kidney stones, frequent urination, blood disorders, and they can make your food, soda, or beer taste terrible.
Side effects of the eye drop include stinging, burning, metallic aftertaste, blurry vision, corneal endothelial cell loss (must be careful in patients with Fuchs’ endothelial dystrophy), and allergy.
The miotics reduce IOP by constricting the pupil, hence opening up the angle of the eye, thereby increasing the drainage of aqueous fluid through the trabecular meshwork. They are no longer commonly used because of their side effect profile, and because other medications have better effects.
The main side effects of the miotics include dim vision (due to constriction of the pupil), headaches above the eyebrow, eye redness and irritation, and retinal detachments.
Combined glaucoma medications afford patients some advantages if they need to be on multiple glaucoma drugs. First, is the convenience factor, in that they only have to remember to use one bottle of medication instead of two. Second, the combo drug sometimes has a lower price.
Side effects of these medications are similar to the side effects of their component medications, which are described above.
Glaucoma surgery has evolved significantly over the past few years, but the surgical therapies still may be put into two categories:
This form of laser therapy is used to treat patients with narrow angles or acute angle-closure glaucoma. In this procedure, your surgeon uses a laser to make a tiny hole in the iris, which allows the aqueous fluid another path to reach the trabecular meshwork.
LTP is used to treat patients with some types of open-angle glaucoma. In some instances, patients may elect LTP instead of medications, or reduce the number of glaucoma medications they are taking. In LTP, a laser is used to treat the trabecular meshwork, thereby, lowering IOP by increasing the amount of fluid that is drained.
Once medical and laser therapies have failed or when they will not work well enough, your doctor may recommend a Trabeculectomy. In this form of surgery, a new drain is made using your eye’s tissue. It has been the gold standard in glaucoma surgical therapy for many years, and new improvements, such as the Express Mini-Shunt have made trabeculectomy surgery safer and more predictable.
In this surgery, the conjunctiva (the eye’s outer covering) is taken down, and a partial-thickness flap is made in the sclera (the white, tough outer covering of the eye). Underneath the scleral flap, the eye is entered allowing a continuous flow of fluid out of the eye. The scleral flap and then the conjunctival tissue is then sutured back into place.
In most cases, your surgeon will use Mitomycin C, which is a chemotherapy agent, to prevent your eye from scarring down the new drain that was surgically developed. In order to allow greater fluid through the new drain, patients most likely will undergo an office-based laser procedure to cut some of the stitches in the scleral flap.
One major development and improvement in trabeculectomy surgery is the Express Mini-Shunt. This is a small metallic device that is placed underneath the scleral flap during surgery. The shunt allows for a predictable egress of fluid from the eye, thereby reducing some of the complications related to an eye pressure that is too low.
Another option for glaucoma that cannot be controlled with medications is an aqueous shunt.
There are three main types of aqueous shunts that are in use today:
These implants have a plate that is sewn to the sclera, near the insertions of the eye muscles. The tube, which is connected to the plate, is then placed directly into the eye. As a result of this procedure, the aqueous fluid will drain through the tube into the plate, which then allows the fluid to be absorbed by the tissues behind the eye. Tubes have become an increasingly popular treatment for many types of glaucoma, and are considered by many to be safer and more predictable than trabeculectomy surgery.
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