February 2017

 

COVER FEATURE

 

Glaucoma and the cataract patient
Debating the benefits of lens extraction in PACG


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer

 
   



Angle closure in eye before (left) and after (right) cataract surgery. The spots on the superior iris are laser iridoplasty scars that were done in an effort to try and deepen the angle and lower the pressure. That treatment did not work, but cataract surgery lowered the pressure to a normal level.
Source: Reay Brown, MD

Contrasting perspectives prevail despite new evidence in angle closure glaucoma

Glaucoma specialists handle primary angle closure glaucoma (PACG) on a patient-to-patient basis, as no single avenue of treatment can cover all the scenarios encountered in this disease. Lens extraction using phacoemulsification is a new approach for PACG management, often alleviating high IOP, opening the anterior chamber angle, and improving quality of life. Some glaucoma doctors, however, are less convinced than others about the efficacy of lens extraction—in the absence of cataract—as the best way to reduce IOP in these patients. Reay Brown, MD, founding partner, Atlanta Ophthalmology Associates, Atlanta; Joseph Panarelli, MD, glaucoma fellowship director and associate residency program director, New York Eye and Ear Infirmary of Mount Sinai, New York; and Robert Feldman, MD, clinical professor and chairman, Ruiz Department of Ophthalmology and Visual Science, University of Texas McGovern Medical School, Houston, spoke with EyeWorld about their treatment preferences for PACG.

All for it

According to Dr. Brown, doctors are now looking at the glaucoma patient in new ways. The role for cataract surgery in angle closure is expanding, and he thinks that the pressure reduction achieved by modern phacoemulsification has elevated lens-based glaucoma surgery to the forefront of glaucoma treatment. As most patients will eventually need cataract surgery, doctors have all the more reason to factor lens removal into their overall treatment plan.
“We see patients everyday in our practices from the pre-phacoemulsification era with peripheral anterior synechiae, secondary angle closure, chronic inflammation, and other problems from extracapsular surgery that contribute to their glaucoma,” Dr. Brown said. “Modern phacoemulsification can help glaucoma patients avoid the worsening of their pressure control caused by these now avoidable complications. Does a diagnosis of glaucoma change the indications for cataract surgery? Clearly, yes. There seem to be few clinical situations in PACG in which lens removal is not beneficial and preferred over laser treatment or a phaco trabeculectomy.”
Dr. Brown’s views coincide with the newest evidence in support of lens extraction from the recently published, multicenter, randomized, controlled Effectiveness in Angle Closure Glaucoma of Lens Extraction (EAGLE) study.1 EAGLE investigated the benefits of early clear lens extraction in 419 patients newly diagnosed with primary angle closure and IOPs in excess of 30 mm Hg, or with PACG, who underwent either lens extraction or laser iridotomy (LI). It demonstrated the greater efficacy and cost effectiveness of clear lens extraction over peripheral LI and suggested that clear lens extraction be considered as an option for first-line treatment in PACG.
Eyes with angle closure will typically present as short eyes with shallow anterior chambers. It is thought that the increasing thickness of the aging lens also contributes to a progressive narrowing of the angle. Meanwhile, LI widens the anterior chamber angle, some degree of iridotrabecular contact persists in most patients, and angle closure may progress despite an iridectomy. Dr. Brown explained, “The anatomy of angle closure eyes supports a therapeutic role for lens removal. Removal of the lens clearly deepens the chamber and opens the angle. Combining the anatomical evidence with the clinical success of cataract surgery has led to discussions about whether clear lens extraction should be recommended for patients with angle closure. There are no studies on the role of clear lens extraction in treating angle closure, however, if the anterior segment anatomy is the problem, and it frequently is, removing a clear lens may have the same positive effects as removing a cloudy lens.”
In a review of studies surrounding lens extraction in PACG,2 Dr. Brown demonstrated a strong body of evidence in favor of cataract surgery for angle closure patients to reduce IOP and dramatically reduce the future risk of IOP spikes and acute attacks. Cataract surgery was found to be a more effective treatment for an attack of acute primary angle closure than laser iridotomy. It also demonstrated better outcomes when compared to phaco trabeculectomy, which showed a higher complication rate than phaco alone. He showed evidence that described an increased risk of 50% for requiring cataract surgery in patients undergoing trabeculectomy, with the added risk of the subsequent cataract surgery, threatened function of the bleb, and loss of any benefit to the IOP of removing the lens primarily. Although Dr. Brown combines goniosynechialysis with clear lens extraction to help to reduce IOP, no studies have compared the risks and benefits of phaco with goniolysis using phaco alone.
In his practice, Dr. Brown has seen many cases where pressures have normalized with cataract surgery alone. A classic case in point was a 45-year-old patient with PACG and a clear lens, who had undergone LPI and iridoplasty but still had IOP of more than 30 mm Hg and was on maximum dosages of medications. The patient began showing increased optic nerve cupping, even though the visual field was full. In the absence of cataract, many surgeons would have recommended a trabeculectomy. However, after many consultations with the patient and another specialist, who recommended a trabeculectomy, the patient opted for clear lens extraction. The 5-year results show normal IOP and the patient is medication-free.
Dr. Brown has also performed clear lens extractions for angle closure issues in more than 20 patients who had small fixed pupils from previous pilocarpine use and iris epithelium adherence to the anterior lens surface from repeated laser iridoplasty in unsuccessful attempts to pull the iris out of the angle. The patients were highly hyperopic (up to +18) with short eyes and very shallow chambers, some requiring pars plana vitrectomy to have enough anterior chamber room for surgery. These risk factors make cataract surgery/clear lens extraction in this group very difficult, and Dr. Brown thinks that performing early lens removal would help avoid unnecessary complications and reduce the future risk from pressure damage. He said, “Predicting which angle closure patients will benefit from lens removal—whether clear or cataractous—remains uncertain. Concerns about clear lens extraction generating high volumes of unnecessary surgery are unfounded because, in practice, truly clear lenses are not common in patients who have had acute attacks or have chronic glaucoma, and who will usually also have multiple risk factors.”

Grain of salt

As would be expected, there is another valid side to this argument. To Dr. Panarelli, cataract surgery is still more of a solution for patients with visual complaints due to cataract and to be considered with caution for PACG patients. He told EyeWorld, “I was trained to perform cataract surgery on people with visual complaints that impinge upon their daily activities; early lens extraction as a treatment for glaucoma is a completely new approach for me. Although there have been studies showing that lens removal can reduce the IOP in patients with open and closed angle glaucoma, many of us prefer to stick to our classic treatment algorithm when managing glaucoma, instituting medical and laser therapy first and then moving to traditional glaucoma surgery if the intraocular pressure is too high for the degree of disc damage.”
Dr. Panarelli’s first choice for treatment of a narrow angle is a laser iridotomy. If there is elevated intraocular pressure, he begins medication and considers iridoplasty, especially in those patients with plateau iris syndrome or nanophthalmos. If these measures do not adequately reduce the IOP, he considers doing filtering surgery. He explained, “New study results do not change my practice patterns that quickly. I am always open to the results of new studies, but I think you have to look at each individual patient as the results/conclusions do not apply directly to every patient you see. Not every new study—even with encouraging results—will impact your clinical practice in a definitive way. In the end, you still need to do what is best in your hands.”
Looking at the clinical impact of eight landmark glaucoma trials, Dr. Panarelli noted substantial differences in the way randomized clinical trials affected actual clinical practices, owing to factors like study timing, design, conduct, and interpretation of results.3 Acknowledging that eye doctors want to provide the highest standards of care, he explained, “We want to be on the cutting edge, but we know that for our patients it isn’t always the newest thing out there that is gaining a lot of press that is best. We have to look at these studies, critically review them, and see if this is best for our patients, especially if we are talking about doing something invasive, when we otherwise might not have. I am not 100% ready to change my ways and perform cataract surgery routinely in this more challenging patient population.” That said, Dr. Panarelli noted that he is open to changing his approach, especially if the patient has had a less than ideal outcome with a previous method of treatment in the contralateral eye.
Dr. Panarelli encourages the use of certain MIGS devices in patients with PACG, assuming synechiae do not hamper visualization of the outflow pathway, which a number of MIGS devices rely on for strategic stent placement. Goniosynechialysis can help restore aqueous flow, reduce IOP, and possibly even allow later stent implantation in the primary outflow pathway. It is thought to be most effective when performed early on in the process, i.e., within 6 months of synechiae formation. When present for greater periods of time, however, breaking synechiae may cause more damage to the canal network. Using the XEN Gel Stent (Allergan, Dublin, Ireland) in cases where the physiologic outflow through Schlemm’s canal and the trabecular meshwork is compromised offers surgeons a new treatment option. The XEN stent shunts fluid from the anterior chamber to the subconjunctival space. Although traditionally glaucoma surgeons have avoided shunt placement in the already shallow anterior chamber out of concern about endothelial cell loss, the 6 mm XEN Gel Stent just barely protrudes into the eye and should be a safe, viable alternative in patients with PACG.

Tell all: PAS

For Dr. Feldman, who does sometimes perform clear lens extraction for angle closure, the EAGLE study does not always translate. “Not everyone has pressures of 30 mm Hg like the participants of the EAGLE study. Most patients that I manage don’t. We are catching them before that happens and treating them before their pressures go up that high. I do not perform lens removal in PACG because of high pressure, but rather to fix the anatomy to prevent additional angle closure. The determining factor is how much peripheral anterior synechiae (PAS) they have and if I think I can get the closed angle working again,” he said.
Lens removal can be effective in lowering IOP in PACG patients who have less than 270 degrees of PAS. Dr. Feldman couples lens removal with additional measures, as needed, to reduce the IOP or open the angle, depending on the anatomy captured on imaging. He considers cataract surgery alone in patients with even up to 270 degrees of PAS, without the need for additional glaucoma surgery. With more than 270 degrees of PAS, lens removal may not suffice to lower IOP because of the paucity of viable trabecular meshwork draining the eye, and he will opt for glaucoma surgery alone if there is no visually significant cataract and combined if there is.
Dr. Feldman thinks it is important to address the potential causes of angle closure when possible. While cataract surgery may deepen the anterior chamber, it may not be the lone cause of the problem. If the angle remains closed or narrow after cataract surgery or LPI, it can often be traced back to an anteriorly rotated ciliary body. Patients may benefit from endocycloplasty in these cases and if diagnosed preoperatively with an ultrasound biomicroscope may be combined with clear lens extraction. The procedure is performed after cataract surgery and IOL implantation and involves the use of the endoscope’s laser attachment to shrink the posterior ciliary process, which allows the ciliary muscle to rotate back and open the angle.
“We still don’t know what the long-term outcomes are of lens removal in PACG,” Dr. Feldman said. “We have 3-year data that says it costs less to take out the lens, that vision and quality of life are better, and that IOP is lower for a few years, but this comes as no big surprise because that is what happens when you take out a cataract in any patient. We don’t know if the additional deepening that you get from lens extraction—and getting additional deepening is an assumption from data from sources other than EAGLE, which you do not get from iridotomy—changes the outcome and prevents progression of the actual angle closure and ultimately, the glaucoma long term.”

References

1. Azuara-Blanco A, et al. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): A randomised controlled trial. Lancet. 2016;388:1389–1397.
2. Brown RH, et al. Lens-based glaucoma surgery: Using cataract surgery to reduce intraocular pressure. J Cataract Refract Surg. 2014;40:1255–1262.
3. Panarelli JF, et al. Clinical impact of 8 prospective, randomized, multicenter glaucoma trials. J Glaucoma. 2015;24:64–68.

Editors’ note: Dr. Panarelli has financial interests with Aerie Pharmaceuticals (Irvine, California) and Allergan. Drs. Brown and Feldman have no financial interests related to their comments.

Contact information

Brown
: reaymary@comcast.net
Feldman: rfeldman@cizikeye.org
Panarelli: ilana.nikravesh@mountsinai.org