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Publication Exclusive: Disruptive changes ahead in glaucoma space
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All of us who do cataract surgery see a significant number of patients who have glaucoma as a comorbidity. At least 10% of patients who come to have cataract surgery also have a diagnosis of glaucoma or ocular hypertension, and a review of Medicare statistics suggests the number may approach 20% in the over-65-year-old population.
During the first two decades of my practice, if a patient presented with combined cataract and glaucoma, I always recommended a combined phacoemulsification and trabeculectomy, because in those days I was invading prime conjunctiva by doing a conjunctival peritomy for my cataract surgery and operating superior. After switching to temporal clear corneal cataract surgery, I began to treat more of my patients presenting with combined cataract and glaucoma with phacoemulsification alone, reserving trabeculectomy for those who did not achieve good IOP control with phacoemulsification combined with argon or selective laser trabeculoplasty and/or topical drops.
My associates Tom Samuelson, MD, Brooks Poley, MD, and I became impressed that phacoemulsification alone was a powerful tool in the treatment of glaucoma and that those most in need presenting with higher preoperative IOP were achieving greater pressure reduction than those with lower pressure. I therefore stopped doing combined procedures altogether.
In one outstate Minnesota satellite clinical setting where I performed only phacoemulsification on 180 patients a year for a decade, with approximately a 15% incidence of glaucoma, I did not have a single patient who went on to trabeculectomy or tube shunt. We performed a retrospective review and published our findings, concluding that phacoemulsification alone can significantly reduce IOP and medication burden in the glaucoma and ocular hypertensive patient.
Perhaps the best confirmative study is the control group in the Glaukos iStent prospective FDA clinical trial, in which a mean IOP drop of 8.4 mm Hg was achieved with phacoemulsification alone in a large group of patients with mild to moderate glaucoma and a preoperative washout IOP near 26 mm Hg. Phacoemulsification alone generated an average IOP near 18 mm Hg in combination with one topical medication. Most of the patients with phacoemulsification alone will still require one or more topical drops for good pressure control, but most patients avoid the risks of a trabeculectomy or tube shunt.
The Tube Versus Trabeculectomy Study confirmed the great efficacy of these procedures, with both generating an IOP near 13 mm Hg, again typically on one topical medication. This is a lower pressure than we can achieve with phacoemulsification alone, and in patients with significant glaucoma damage in which a very low pressure is indicated, these operations remain an important tool. However, the efficacy of cataract surgery alone in reducing IOP and now the availability of an FDA-approved microinvasive glaucoma surgery (MIGS) device, the iStent, have significantly reduced the number of patients who require the much more invasive tube shunt or trabeculectomy.
Click here to read the full publication exclusive, Lindstrom's Perspective, published in Ocular Surgery News, U.S. Edition, February 25, 2016.