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Role of medication may change because of new surgical glaucoma devices
New technologies have made glaucoma surgery less invasive and less risky, making it a treatment option even for patients with mild or moderate disease.
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 Eric D. Donnenfeld |
The treatment paradigm for glaucoma management is evolving rapidly. Newer alternatives have become available that enhance patient quality of life and compliance with glaucoma therapy. As a result, clinicians are changing their impressions of what is acceptable with glaucoma interventions, and they are better able to meet the demands of their patients. New technologies have made glaucoma surgery less invasive and less risky, making surgery more likely to be used earlier in the treatment algorithm. Surgery is no longer considered a “last resort” treatment option, but rather is something to be considered in patients with mild or moderate disease.
Traditionally, patients with glaucoma were placed on treatment with one, two, three or sometimes even four separate medications. The ocular surface irritation, expense and dosing compliance difficulties were considered issues that had to be accepted by glaucoma patients.
Medication drawbacks
Topical glaucoma medications not only cause tolerability problems but can also have significant local and systemic side effects. Prostaglandins can cause changes to the pigmentation of the iris and skin around the eye but may also prolong postsurgical inflammation that, in turn, may increase the risk of cystoid macular edema. Topical carbonic anhydrase inhibitors may cause a decrease in corneal endothelial function, which can result in corneal edema. Oral carbonic anhydrase inhibitors may cause hypoglycemia, tingling or loss of strength of the hands and feet, upset stomach, depression, memory problems, kidney stones and frequent urination. Locally, beta-blockers can cause corneal anesthesia as well as irritation and dry eye symptoms. In addition, there is a well-established association between beta-blockers and systemic side effects such as depression, impotence and cardiac arrhythmias, as well as sudden death in extreme cases.
Glaucoma medication costs are closely linked to treatment compliance. Many patients pay co-pays of $20 to $50 every month for each of their glaucoma medications. Medications have to be administered several times per day to maintain optimal control, and even missing one dose could cause a spike in IOP, which in turn could lead to optic nerve damage and disease progression. Historically, when the medications no longer worked and no other options remained, patients were presented the option of fairly invasive surgical procedures that had significant risks.
The new, evolving standard is that patients do not need to be on therapy with multiple medications for long periods of time when being treated for glaucoma. Previously, the only available glaucoma surgical procedures were tube shunts and trabeculectomies. These were very invasive surgeries that involved large incisions into the eye with the subsequent risks of hypotony and endophthalmitis. Frequently, the risks of surgery outweighed the inconvenience, expense and side effects of medications.
New surgical technologies
Now there are new surgical options that are becoming available that will give patients a safe and reliable reduction of IOP with the potential to reduce or eliminate the need for glaucoma medications. Trabecular micro-bypass stents that can be inserted at the time of cataract surgery or done as independent procedures have revolutionized the glaucoma surgical arena. The development of trabecular micro-bypass technology promises to control IOP while allowing the patient to maintain their visual fields and lead a more normal, comfortable life, without the expense of costly medications.
Three new technologies currently available are focused on re-establishing pressure-dependent aqueous outflow to restore physiologic drainage of the aqueous, thus controlling IOP: canaloplasty (iScience International), Trabectome (NeoMedix) and iStent (Glaukos).
The iStent recently received strong support from the U.S. Food and Drug Administration Ophthalmic Panel, and the premarket approval application is currently undergoing review by the FDA. In practice, the iStent is placed into the trabecular meshwork through the same small, temporal, clear corneal incision used for phacoemulsification — or through an incision less than 1 mm if the stent is implanted as a stand-alone procedure. The iStent is implanted ab interno, thereby preserving the conjunctival tissue and eliminating the serious complications associated with end-stage filtering procedures. The procedure has minimal to no risk of hypotony due to the physiologic preservation of the trabecular meshwork, aiming to ensure the natural episcleral back pressure of 8 mm Hg to 11 mm Hg. Patient trials showed a mean reduction of 1.2 medications with one stent employed, with the option of titrating therapy by implanting two or three stents when additional pressure control is needed.
Compared to the previous generation of glaucoma surgeries, the iStent procedure is dramatically less invasive and has far fewer side effects. The safety and efficacy profile is such that, as a cataract surgeon, I now feel comfortable recommending that cataract surgeons be involved in glaucoma surgical management. In the past, I referred my glaucoma patients to glaucoma specialists to manage. Now I feel comfortable offering my mild-to-moderate open-angle glaucoma patients the iStent technology as part of a comprehensive cataract procedure.
Shifting treatment model
Moving forward, there will be a paradigm shift in ophthalmology and specifically in glaucoma management. While there will still be a need for glaucoma medications, the iStent technology will move surgery to the forefront as a cost-effective treatment. As doctors and patients seek better IOP control and improved quality of life, medication will be moved into a secondary position for controlling glaucoma. As opposed to adding a second and third medication to a patient’s regimen, I predict that patients will likely start with one medication and then, if more pressure control is needed, go to microstent technology before additional medications are prescribed. Also, any patient with mild-to-moderate open-angle glaucoma should consider an iStent implantation at the time of cataract surgery, while the doctor is already inside the eye and able to provide a comprehensive cataract procedure that provides long-term pressure control and an improved quality of life.
References:
- Fea AM. Results of phacoemulsification compared with phacoemulsification and stent implantation in patients with POAG at 15 months. Abstract presented at: Annual Meeting of the American Academy of Ophthalmology; November 8-12, 2008; Atlanta, GA.
- Nichamin LD. Glaukos iStent trabecular micro-bypass. Middle East Afr J Ophthalmol. 2009;16(3):138-140.
- Eric D. Donnenfeld, MD, FACS, can be reached at Ophthalmic Consultants of Long Island, 2000 N. Village Ave., Rockville Centre, NY 11570; 516-766-2519; fax: 516-766-3714; e-mail: eddoph@aol.com. Dr. Donnenfeld is a consultant for Glaukos.
