WHAT IS GLAUCOMA?

Glaucoma is a disease of the optic nerve, which transmits the images you see from the eye to the brain. The optic nerve is made up of many nerve fibers (like an electric cable with its numerous wires). Glaucoma damages nerve fibers, which can cause blind spots and vision loss.

Glaucoma can be related to the pressure inside the eye, known as the intraocular pressure (IOP). When the aqueous humor (a clear liquid that normally flows in and out of the eye) cannot drain properly, pressure builds up in the eye. The resulting increase in IOP can damage the optic nerve and lead to vision loss.

GLAUCOMA TREATMENT

While there is no cure for glaucoma, it can be controlled with proper management.

Elevated intraocular pressure (IOP) can damage the optic nerve, which may lead to vision loss. Treatment for glaucoma focuses on lowering the IOP to a level that is less likely to cause further optic nerve damage. This is known as the “target pressure.” The target pressure differs from individual to individual. Your target pressure may change during your course of treatment.

If you have glaucoma, your ophthalmologist may prescribe a medication to lower your eye pressure. For glaucoma medications to work, you must take them regularly and as prescribed by your doctor.

MEDICATION TIPS

With each new medication that your ophthalmologist prescribes, make sure you understand the following:

  • the name of the medication;
  • how to take it;
  • how often to take it;
  • how to store it;
  • if you can take it with your other medications (make sure all of your doctors know about all the different medications you take, including nonprescription medications);
  • what the possible side effects may be;
  • what you should do if you experience side effects; and
  • what you should do if you miss a dose.

There are several different medications available for the treatment of glaucoma including 1) beta-blockers, 2) prostaglandin analogues, 3) Alpha agonists, 4) carbonic anhydrase inhibitors, and 5) combined agents.

BETA-BLOCKERS IN THE TREATMENT OF GLAUCOMA

How Do Beta Blockers Work?
Beta-blocker (beta adrenergic antagonist) medications are reliable for lowering intraocular pressure. They work by decreasing the amount of fluid that the eye continually produces, called the aqueous humor. For many years, beta blockers were the mainstay of treatment. Thus, we have a lot of experience with this medication for the treatment of glaucoma.

Types of Beta-Blocker Medications
There are two general classes of beta blockers: nonselective and selective. Nonselective beta blockers have more effects on the body’s beta receptors system-wide and are associated with more side effects. The nonselective beta blockers are also more effective at lowering IOP.

The nonselective beta blockers include

  • levobunolol (Betagan, AKBeta);
  • timolol (Timoptic); and
  • timolol gel (Timoptic XE).
  • Generic versions of timolol and timolol gel are now available. Consult with your ophthalmologist to be sure that a generic product is an acceptable alternative for you.

The only available selective beta-blocker medication is

  • betaxolol (Betoptic, Betoptic S).
  • Betaxolol is the generic form of Betoptic.

While a selective beta-blocker eyedrop has a better safety profile, especially in terms of respiratory symptoms, it still must be used with caution in patients with asthma or emphysema. The eye pressure-lowering effect is slightly less with selective beta blockers. There is only a minimal additive effect in terms of lowering eye pressure in patients already taking oral beta blockers, and there is the risk of further additive side effects. If you are already taking a beta-blocker medication by mouth or if your primary care doctor newly prescribes a beta blocker, please notify your ophthalmologist.

Possible Side Effects of Beta Blockers
All medications, including eyedrops, can have side effects. Some people taking beta-blocker eyedrops may experience

  • wheezing or difficulty breathing;
  • slow or irregular heart beat or decreased response of heart rate to exercise;
  • increased risk for heart failure;
  • depression;
  • impotence;
  • headache, dizziness or weakness;
  • in diabetics, difficulty sensing blood glucose changes; and
  • eye irritation or allergy.

PROSTAGLANDIN ANALOGS/PROSTAMIDES IN THE TREATMENT OF GLAUCOMA

How do prostaglandin analogs or prostamides work?
Prostaglandin analogs and prostamides lower IOP by increasing the outflow of the aqueous humor, the fluid made continuously by the eye. All of these medications are taken once a day, except for Rescula, which is taken twice per day.

What are the prostaglandin analog and prostamide medications?

  • latanoprost (Xalatan)
  • bimatoprost (Lumigan)
  • travoprost (Travatan) Lumigan

Possible side effects of prostaglandin analogs or prostamides
All medications, including eyedrops, can have side effects. Some people taking these eyedrops may experience:

  • redness of the eye
  • darkening of the iris (the colored part of the eye); this color change occurs slowly and may not be noticeable for months or even years;
  • increased growth, thickness, and pigmentation of the eyelashes;
  • eye irritation or itching;
  • blurred vision;
  • darkening of the eyelid skin;
  • muscle aches (rare); and
  • headaches (rare). Xalatan

Patients with a history of uveitis (inflammation in the eye), ocular herpes infection, or swelling in the retina (called cystoid macular edema) should use this medication with caution. If you have a history of any of these conditions, please discuss it with your doctor.

ALPHA-AGONISTS IN THE TREATMENT OF GLAUCOMA

How Do Alpha Agonists Work?
Alpha agonist medications are reliable for lowering the intraocular pressure. They work by decreasing the production of the fluid that the eye continually makes, called the aqueous humor.

What Are the Alpha Agonists?

There are three alpha agonist drugs:

  • apraclonidine (Iopidine);
  • brimonidine (Alphagan, Alphagan P); and
  • dipivefrin (Propine).

A generic version of Alphagan called brimonidine is available.

Possible Side Effects of Alpha Agonists
All medications, including eyedrops, can have side effects. Some people taking alpha agonist eyedrops may experience:

  • dry mouth;
  • ocular allergy with a red eye or red eyelids (30% of patients);
  • tiredness or fatigue;
  • low or high blood pressure and possible slowing of heart rate (less than with beta blockers);
  • blurred vision;
  • sensitivity of the eyes to bright light; and
  • headache.

COMBINED AGENTS IN THE TREATMENT OF GLAUCOMA

Several eyedrops are available that combine the actions of two drugs from different categories. The reasoning behind the use of combined agents is that it is easier for patients to put just one drop in their eyes instead of two; it may also be healthier for the eye as less preservative is being applied.

What are the combined medications?

  • Combigan (Combines a beta-blocker and an alpha-agonist)
  • Cosopt (Combines a beta-blocker and a CAI)
  • DuoTrav (Combines a prostaglandin analog and a beta-blocker)
  • Xalacom (Combines a prostaglandin analog and a beta-blocker) DuoTrav

For glaucoma medications to work, you must take them regularly and continuously as prescribed by your doctor.

GLAUCOMA SURGERY

If you have glaucoma and medications and laser surgeries do not lower your eye pressure adequately, your ophthalmologist may recommend you be evaluated by a glaucoma specialist to evaluate your suitability for a procedure called a trabeculectomy.

In this procedure, a tiny drainage hole is made in the sclera (the white part of the eye). The new drainage hole allows fluid to flow out of the eye into a filtering area called a bleb. The bleb is mostly hidden under the eyelid. When successful, the procedure will lower your intraocular pressure (IOP), minimizing the risk of vision loss from glaucoma. The surgery is performed in an operating room on an outpatient basis.

Some of the risks and complications from trabeculectomy surgery include the following:

  • failure to control intraocular pressure, with the need for another operation;
  • infection;
  • bleeding in the eye;
  • swelling in the eye;
  • irritation or discomfort in the eye;
  • eye pressure that is too low;
  • cataract (in cases where cataract has not already been removed); and
  • decreased or lost vision.

Antimetabolites
Certain medications, called antimetabolites, were originally developed to help treat some kinds of cancer. These same medications have also been found to be helpful when used with some types of glaucoma surgery.

These medicines may be applied to the eye during or after the surgery to reduce the growth of scar tissue, a common cause of failure in glaucoma surgery. Mitomycin-C and 5-fluorouracil (5-FU) are the most commonly used antimetabolites for glaucoma surgery. When these antimetabolites are used with other medications that reduce inflammation, the success rate of surgery is greatly improved, especially for patients who are at high risk for excessive scarring.

Your glaucoma specialist may consider using antimetabolite medicines with your glaucoma surgery if:

  • you are having surgery on an eye that has been operated on before;
  • you have inflammation in your eye (called uveitis);
  • you have glaucoma due to new blood vessel formation within the eye;
  • you are having glaucoma and cataract surgery at the same time;
  • you are relatively young;
  • you have more deeply pigmented skin; or
  • your eyes are at risk for postoperative scarring.

In addition to the usual complications of glaucoma surgery, other risks associated with using antimetabolites include:

  • eye pressure that is too low;
  • leaking incisions;
  • slower healing of the cornea;
  • blurred vision;
  • fluid in or behind the retina;
  • thinning of the eye tissues; and
  • infection.

If your glaucoma specialist has decided to use antimetabolite medications, he or she will explain why they are recommended for you. While some people may experience side effects from medications or surgery, the risks associated with these side effects should be balanced against the greater risk of leaving glaucoma untreated and losing your vision.