August 2020


What placing an iStent means to refractive cataract results

by Maxine Lipner Contributing Writer

iStent in Schlemm’s canal
Source: John Berdahl, MD


With cataract surgery becoming more and more of a refractive procedure in terms of technologies and patient expectations, how would placing an iStent (Glaukos) at the time of cataract surgery to lower IOP in a patient with open angle glaucoma affect refractive results?
A retrospective study1 found that outcomes with the iStent were comparable to cases where only cataract surgery itself was performed, according to John Berdahl, MD. “Because patients in the mild-to-moderate category of glaucoma are frequently getting IOLs to treat astigmatism and sometimes presbyopia, we thought it was important to understand if the stents had refractive effects that could make these lenses less successful,” Dr. Berdahl said.

Comparing results

Included in the series were 76 consecutive patients with open angle glaucoma who were undergoing cataract surgery with implantation of an iStent. Fifty patients without open angle glaucoma served as controls and had cataract surgery only. “We looked at what we were predicting for refractive outcomes, and we found that there wasn’t a difference between the two groups,” Dr. Berdahl said, adding that it appeared the refractive effect of iStent was neutral.
Forty-six percent of patients who received the combined procedure were within 0.25 D of target spherical equivalent vs. 52% of patients who had cataract surgery alone. Meanwhile, 80% in either group were within 0.50 D of targeted correction, Dr. Berdahl noted, adding that astigmatism outcomes were not different between the groups. Investigators found that 51% of those in the combined group were within 0.5 D of targeted astigmatism correction vs. 32% of those in the cataract-only group.

Clinical perspective

Dr. Berdahl views this as good news clinically. “It means that surgeons don’t have to wonder if an iStent has a refractive effect,” he said. “What the surgeon needs to wonder is if the patient wants a refractive outcome and would their glaucoma or other disease preclude them from a refractive IOL.”
They may also need to consider what type of refractive IOL is appropriate for the patient. “We know that for patients who have astigmatism, in a patient with mild-to-moderate glaucoma and iStent, this should not be an exclusionary criteria for a toric IOL,” Dr. Berdahl said, adding that multifocal lenses are different due to decreased contrast sensitivity associated with glaucoma. “But newer generation multifocal IOLs have been shown in photopic and scotopic conditions not to decrease contrast sensitivity,” he said. “So surgeons are starting to use multifocality in patients with mild glaucoma.”
Dr. Berdahl said he would consider these IOLs in patients who don’t have visual field defects and mild glaucoma. “But an important point here is can you hit the refractive target, and this shows that the addition of an iStent doesn’t decrease the likelihood of this,” he said.
When considering iStent in conjunction with refractive lenses, Dr. Berdahl advised practitioners listen to the patient and understand how they want to use their eyes. “Don’t think that a patient who has mild-to-moderate glaucoma can’t get a good refractive outcome—they can,” he said, adding that practitioners should be facile with technologies such as toric, multifocal, and extended depth of focus lenses that can help patients achieve such outcomes. “Finally, think about the progression of the disease,” he said. “If glaucoma is going to decrease contrast sensitivity further over time, would you be comfortable with that patient having a multifocal lens in their eye?”
Overall, Dr. Berdahl hopes that practitioners keep patient expectations in mind. “As patients get more and more demanding, we need to do our best to match the right technologies with the patient expectations and give them the best possible chance of using their eyes the way they want for the rest of their lives,” he concluded.

About the doctor

John Berdahl, MD
Vance Thompson Vision
Sioux Falls, South Dakota


1.Scott RA, et al. Refractive outcomes after trabecular microbypass stent with cataract extraction in open-angle glaucoma. Clin Ophthalmol. 2019;13:1331–1340.

Relevant disclosures

Berdahl: Alcon, Allergan, Bausch + Lomb, Glaukos, Johnson & Johnson Vision, New World Medical, RxSight, Sight Sciences



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