Managing glaucoma: A full-spectrum approach

November 8, 2008

The 1990s brought a decade of advances in the medical therapy of glaucoma. That decade saw the introduction of a new carbonic anhydrase inhibitor, dorzolamide (Trusopt, Merck); the first prostaglandin, latanoprost (Xalatan, Pfizer); the first alpha-2 agonist, brimonidine (Alphagan, Allergan); and the first fixed-combination carbonic anhydrase inhibitor/beta-blocker, dorzolamide and timolol (Cosopt, Merck).

The 1990s brought a decade of advances in the medical therapy ofglaucoma. That decade saw the introduction of a new carbonicanhydrase inhibitor, dorzolamide (Trusopt, Merck); the firstprostaglandin, latanoprost (Xalatan, Pfizer); the first alpha-2agonist, brimonidine (Alphagan, Allergan); and the firstfixed-combination carbonic anhydrase inhibitor/beta-blocker,dorzolamide and timolol (Cosopt, Merck).

These new drugs did much to improve problems common with theavailable formulary, such as local and systemic side effects andpoor compliance. Adherence with therapy, however, remains abarrier to effective patient management. In the years since thosedrugs became available, efforts have continued to find ways ofsimultaneously bringing about reductions in IOP and doing so in away that encourages compliance, suggested Jason Bacharach, MD.Dr. Bacharach is associate professor of ophthalmology andco-chairman of the glaucoma division at California PacificMedical Center, San Francisco.

He was one of several speakers at a breakfast continuingeducation symposium held during the American Academy ofOphthalmology annual meeting in Atlanta. The program was held atthe Atlanta Marriott Marquis. The chairman and moderator was JoelS. Schuman, MD, Eye and Ear Foundation Professor and chairman,Department of Ophthalmology, University of Pittsburgh School ofMedicine. Dr. Schuman also is director of the University ofPittsburgh Medical Center Eye Center.

One of the new approaches in glaucoma monotherapy is thedevelopment of drugs that do not contain the preservativebenzalkonium chloride (BAK), which can have negative effects onthe ocular surface. A BAK-free formulation of travoprostophthalmic solution 0.004% (Travatan Z, Alcon Laboratories),which instead uses a novel, ionic-buffered preservative system(SofZia), appears to have IOP-lowering power equivalent to theoriginal formulation, Dr. Bacharach said.

The formulation of beta-blockers also has been updated. Potassiumsorbate has been added to a timolol maleate formulation (Istalol,Ista Pharmaceuticals). The potassium sorbate enhances timololabsorption into the anterior chamber and enables once-dailydosing.

Adjunctive options also have been enhanced in recent years. Afixed combination of brimonidine tartrate-timolol maleateophthalmic solution 0.2%/0.5% (Combigan, Allergan) was approvedin 2007. Studies suggest that adverse events related toconjunctival allergy or inflammation are significantly lesscommon with the fixed combination than with brimonidine alone,Dr. Bacharach said.

These new drugs increase clinicians’ ability to customize therapyand may improve compliance, he added.

Laser therapy also has a place in the treatment paradigm foropen-angle glaucoma, said L. Jay Katz, MD, professor ofophthalmology, Jefferson Medical College, and director of theGlaucoma Service, Wills Eye Institute, Thomas JeffersonUniversity, Philadelphia. He cited results of the Glaucoma LaserTrial and a follow-up study, which indicated that initialtreatment with argon laser trabeculoplasty was at least asefficacious as initial treatment with topical medication. Inaddition, a new clinical study comparing selective lasertrabeculoplasty versus topical medical therapy as initialmonotherapy has begun in the United States and Canada. Issuesbeing addressed in the study include IOP control, compliance,cost, and patient preference.

Reviewing results of the Collaborative Initial Glaucoma TreatmentStud (CIGTS), Dr. Katz also reported that filtration surgery andmedical management both effectively lower IOP and prevent visualfield loss. Overall, the surgical group in the CIGTS studyreported a greater decline in symptom impact over time.

In sum, the findings from these trials imply that a re-evaluationof the treatment paradigm of moving from maximal medical therapyto laser trabeculoplasty to filtering surgery may be timely, Dr.Katz concluded.

Robert J. Noecker, MD, MBA, also spoke at the symposium,discussing detection and monitoring for long-term care. He is anassociate professor in the Department of Ophthalmology at theUniversity of Pittsburgh School of Medicine. In his talk, henoted that while IOP measurements are essential, they areunsuitable as a stand-alone means of monitoring progression.

Visual field assessment is one way of gaining additionalinformation about the patient’s status, although a large numberof tests are needed to confirm progression because this techniqueis prone to extensive variation and is highly subjective.

Clinical assessment of the optic nerve head and nerve fiberlayers also provides details useful for long-term patientmanagement, as do optic disk stereophotographs, Dr. Noecker said.To get the most complete assessment possible, these strategiesshould be supplemented with use of imaging devices such asoptical coherence tomography and confocal scanning lasertomography (Heidelberg Retinal Tomograph, HeidelbergEngineering), according to Dr. Noecker. Imaging devices provide aquantitative and sensitive method of detecting diseaseprogression.

This continuing medical education activity was jointly sponsoredby the New York Eye and Ear Infirmary and cme², inpartnership with Ophthalmology Times, and is supportedthrough unrestricted educational grants from HeidelbergEngineering GmbH, ISTA Pharmaceuticals, and Lumenis.

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