THE CHALLENGE OF GLAUCOMA

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What you need to know to manage a newly diagnosed glaucoma patient.

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Glaucoma is a complicated group of diseases that without intervention can progressively cause damage to the optic nerve head tissue, resulting in loss of peripheral vision and eventually blindness.

Currently, it is estimated that three million Americans have glaucoma with only half of them formally diagnosed. Glaucoma is a non-curable disease that, luckily, for most patients under proper care can be slow progressing. As ocular health providers, our main management goal is to lower the intraocular pressure (IOP). Current treatment options for lowering IOP include myriad topical ophthalmic drops, laser procedures and surgical intervention. The least invasive of these treatments and the recommended first line of therapy are topical ophthalmic drops. With so many drugs now available, the question is: Where do you begin with a newly diagnosed glaucoma patient?

MAKING THE DIAGNOSIS
When a patient is diagnosed with glaucoma at our office, there are several measurements needed before making the official diagnosis. It is important to get a full picture of the patient’s ocular health, linking all the various tests that support the diagnosis. These measurements include: patient’s IOP, optical coherence tomography (OCT) of the optic nerve head, a Humphrey automated perimeter 24-2 visual field test (HVF) and Diopsys electroretinography (ERG).

The patient’s corneal thickness and gonioscopy findings should also be considered when making the diagnosis. If the HVF shows a glaucomatous defect, a repeat test is run and analyzed for a consistent defect. When analyzing the OCT, we look for glaucomatous thinning of the retinal nerve fiber layer (RNFL). Our office has both the ZEISS Cirrus-HD 5000 series OCT and Optovue iWellness OCT; both are beneficial in the diagnosis.

Once the patient is diagnosed with glaucoma such as Primary Open Angle, Normal Tension or any other form, the main treatment goal is to halt disease progression. When choosing the ideal drug for treatment the following should be considered: a) decreasing IOP, b) few adverse effects or systemic exacerbation of disease, and c) affordability with once-a-day dosing. Most commonly, the first line of treatment should be the least invasive, which are the topical ophthalmic drops.

PROSTAGLANDIN
In our office, the class of drugs that is our first line of therapy is the prostaglandin analog (PGA). This class of drugs has very few side effects with a 25% to 30% expected reduction in IOP by increasing the uveoscleral outflow. One-drop a day dosing also helps improve compliance. Prostaglandins, as a class, are an ideal drug when treating glaucoma. Our office typically tries to avoid generic drugs, due to decreased efficacy and increased side effects from preservatives. Our first option is to prescribe bimatoprost (Lumigan 0.01% from Allergan). Depending on the patient’s insurance, travaprost (Travatan Z from Alcon Laboratories) is another good option. After using this drop every night in the glaucomatous eyes for four to six weeks, patients return for a follow up of their IOP. If the IOP is at goal, then we monitor again in three to four months.

ALPHA 2-ADRENERGIC AGONIST
If the PGA does not reduce the patients’ IOP enough, they will be re-evaluated with a follow up IOP, OCT and ERG in six to eight weeks. If follow-up testing continues to show abnormalities, we consider adding our second drug of choice, brimonidine 0.1% (Alphagan P 0.1% from Allergan). Brimonidine is within the selective alpha 2-adrenergic agonist drug class with roughly a 20% to 30% expected reduction in IOP. Brimonidine may also be used if there are too many adverse effects to PGA. Brimonidine works by decreasing aqueous humor secretion as well as increasing uveoscleral outflow. Brimonidine is dosed at two to three times a day with the greatest side effect being a follicular conjunctivitis.

Apraclonidine (Iopidine from Alcon Laboratories) is the other alpha 2-adrenergic agonist that could be prescribed, but it has a greater risk for adverse side effects. After using  this drop for another four to six weeks, the patient’s IOP will be re-checked. On both drops, the patient’s IOP typically decreases significantly enough to appropriately manage the glaucoma.

BETA-BLOCKERS
Another drug class to consider as a second line treatment are beta-blockers, which work by decreasing the amount of aqueous humor production. Timolol maleate (Timoptic and Timoptic XE from Valeant Pharmaceutical; Istalol from Bausch + Lomb) is a popular non-selective beta-blocker that is dosed with either one drop every morning or one drop twice a day. Non-selective beta-blockers, like alpha 2-adrenergic agonists, have roughly a 20% to 25% expected reduction. The side effects of beta-blockers are perhaps the most numerous and by far the most serious. Among these serious side effects are bronchospasm, bradycardia and masking hypoglycemia symptoms in diabetic patients. Apart from these severe systemic side effects, beta-blockers tend to cause dry eye.

COMBINATION DROPS
So, if the first two lines of treatment (PGAs and alpha 2-adrenergic agonists) are not adequate, our third line of treatment is typically a combination drop. Brinzolamide/brimonidine tartrate (Simbrinza from Alcon Laboratories) is the most frequently prescribed combination drop in our office. Simbrinza is a good option when looking for a combination drop to manage glaucoma. Brinzolamide is one of the components of Simbrinza, and it is a carbonic anhydrase inhibitor. Carbonic anhydrase inhibitors are dosed twice a day and typically have a 14% to 17% reduction in IOP. Side effects of the topical ophthalmic drops in this category include a bitter taste and punctate keratopathy. The other topical drug in this category is dorzolamide (Trusopt from Merck & Co., Inc.). Carbonic anhydrase inhibitors also create corneal tissue symptoms, albeit to a lesser degree compared to beta blockers. This is why we prefer not to use it as a first or second line of treatment. When brinzolamide is in combination with brimonidine, the percent reduction in IOP makes Simbrinza a good third line treatment. Finally, the other combination drop that our office uses is brimonidine tartrate/timolol maleate (Combigan from Allergan). This combination has comparable efficacy, but the systemic side effects of timolol once again need to be considered.

Patient follow up should be based on how advanced the glaucoma is. After first initiating treatment, a patient should be seen in about four to six weeks to determine how the topical treatment is working. Adjusting treatment at each of these visits is dependent on the patient’s target IOP. Once the target IOP is met and scans show no further progression, the follow up visits do not need to be as frequent. Patients with mild stage glaucoma  can be seen every six months. Moderate stage glaucoma should be evaluated every four months and severe stage glaucoma every three months or sooner.

Glaucoma is a complex disease and its management varies with each patient. This is what makes glaucoma not only challenging in diagnosis but urges a practitioner to consider all possibilities when deciding on management.

Katherine Shen, OD, is an associate at Specialty Eyecare Group in Seattle and Kirkland, WA.

 

WHERE TO FIND IT:
Alcon Laboratories
800.451.3937 | Alcon.com
Allergan
800.347.4500 | Allergan.com
Bausch + Lomb
800.553.5340 | Bausch.com/ECP
Merck & Co., Inc.
908.740.4000 | Merck.com
Valeant Pharmaceuticals International, Inc.
866.246.8245 | Valeant.com

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