September 2018

GLAUCOMA

Research highlight
Power quandary


by Maxine Lipner EyeWorld Senior Contributing Writer


Endoscopic view of ciliary processes with whitening and shrinkage along the left side from ECP

Gonioscopic view of the anterior chamber angle with iStent trabecular bypass device seated in the canal of Schlemm

Cataract with pseudoexfoliation material accumulated on the anterior lens capsule in patient with associated glaucoma
Source (all): Leonard Seibold, MD

Eyeing refractive surprise in glaucoma patients undergoing phaco

Patients who have glaucoma are at a higher risk for issues with IOL power following cataract surgery, according to Leonard Seibold, MD, associate professor of ophthalmology, University of Colorado, Aurora. Results of a study1 published in the Journal of Cataract and Refractive Surgery indicated that 11.2% of those with glaucoma had 1 D or more of refractive surprise compared with 4.9% of controls, Dr. Seibold reported.
Of all of the patients in Dr. Seibold’s database who had undergone phacoemulsification over the last 2 years, approximately 1 in 4 also had glaucoma. It was this concomitant frequency that was part of the impetus of the study. “Also factoring in was the increased demand from patients regarding refractive outcomes after cataract surgery,” Dr. Seibold said. A secondary aim of the study was to assess the effect of MIGS procedures that are done at the time of cataract surgery.

Database review

“We included everyone who underwent cataract surgery over an 8-month period here at the University of Colorado,” Dr. Seibold said. In this retrospective case series, there were 206 eyes with glaucoma placed in one group and 1,162 controls placed in another. Within the glaucoma group, investigators sub-analyzed the variations of the disease to see if any particular type had a higher risk of refractive surprise, and also compared those patients who had cataract surgery alone to those who had cataract surgery with a MIGS procedure.
The key finding overall was that those with glaucoma were more likely to have a refractive surprise and/or a poorer visual outcome after cataract surgery. Investigators determined that 40.3% of those with glaucoma had a refractive surprise greater than 0.5 D, while this only affected 29.9% of the control group. “In the sub-analysis, we found that the highest risk of having a refractive surprise was in patients with chronic angle closure glaucoma and pseudoexfoliation glaucoma,” Dr. Seibold said. Those with chronic angle closure glaucoma had a 14.54 odds ratio of a refractive surprise, while those with pseudoexfoliation glaucoma had a 7.27 odds ratio. In the primary open angle group, the odds ratio was 1.90.
“This was the first study to our knowledge to show that the refractive outcomes aren’t as good in glaucoma patients,” Dr. Seibold said. Since there is more zonular instability in patients with pseudoexfoliation glaucoma, this may mean that the effective lens position can be different than calculations indicate, he noted. “In chronic angle closure patients, they may also have more shift in the lens position after cataract surgery than in someone without glaucoma,” he said. “Another possibility is that glaucoma patients are usually on one or several topical glaucoma drops that can cause ocular surface disease; this may affect the IOL calculations before surgery, leading to inaccurate readings, and that could potentially lead to a higher risk of a refractive surprise.” Dry eye, which disproportionally affects glaucoma patients and can lead to measurement errors, could be a factor.
Investigators determined that undergoing a MIGS procedure in conjunction with cataract surgery was not a significant issue.
While there was some concern that a few patients had prior filtration surgery that might account for a refractive surprise, there was no such association found. “We looked at this and found that filtration surgery was not a risk factor for increased refractive surprise, although the sample size of those patients was somewhat low,” Dr. Seibold said.

Practical approaches

Dr. Seibold advised practitioners who are performing phacoemulsification in this higher risk population to counsel patients that they may be more likely to be spectacle-dependent after surgery. Those considering doing a MIGS procedure in conjunction with cataract surgery, however, can do so without concern that the addition of an iStent (Glaukos, San Clemente, California) or endoscopic cyclophotocoagulation (ECP) would put the patient at a high risk of refractive surprise.
To help minimize the chance of refractive surprise in high risk patients, Dr. Seibold recommended optimizing the ocular surface with aggressive lubrication and possible consideration of prescription dry eye medication prior to doing lens calculations.
“I would also consider doing additional measurements or repeat measurements, particularly in patients who are getting a premium lens in the form of a toric or multifocal lens,” he said, adding that the use of intraoperative aberrometry during the procedure may also help to determine the correct IOL power.
“I think the take-home message is we need to be aware of the fact that glaucoma patients do not do as well refractive-wise after cataract surgery as other patients,” Dr. Seibold said. “We should keep this in mind when counseling patients and when choosing an IOL.” Also, if considering a MIGS procedure, practitioners can do so with confidence, knowing that it’s not going to affect the refractive outcome, he concluded.

Reference

1. Manoharan N, et al. Refractive outcomes of phacoemulsification cataract surgery in glaucoma patients. J Cataract Refract Surg. 2018;44:348–354.

Editors’ note: Dr. Seibold has financial interests with Glaukos.

Contact information

Seibold: Leonard.Seibold@ucdenver.edu

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