October 2020

CATARACT

Optimizing manual small incision cataract surgery outcomes


by Maxine Lipner Contributing Writer


Mature white cataract; small incision cataract surgery is performed by creating a 7–8 mm curvilinear half thickness scleral incision; the crescent blade is used to continue this incision forward, creating a pocket; the incision begins 1.5–2 mm posterior to the limbus, and the pocket is made into the clear cornea by 1.5 mm
Source: Susan MacDonald, MD

Manual small incision cataract surgery (MSICS) is a skill every cataract surgeon should learn, according to Susan MacDonald, MD. It gives a surgeon options and confidence to handle several complex cases, she said. With MSICS, there is limited risk to endothelial cells or dropping of the nucleus or fragments. Most importantly, it provides an excellent result without expensive technology, Dr. MacDonald said. There are several ways to maximize outcomes with this technique that is more commonly employed in areas where phaco is not a viable option.

Minimizing astigmatism

To maximize MSICS outcomes, is important to make an effort to minimize astigmatism. Dr. MacDonald stressed paying attention to preoperative astigmatism; it is possible to reduce astigmatism with the placement of the incision on the steep axis, she said. In a low resource setting, the Maloney Astigmatism Keratometer can help the surgeon evaluate the shape of the cornea at the beginning and end of the procedure. This will help the surgeon decide if a suture could help by placing it on the flat axis, she said. If using a scleral incision, this could be placed further away from the cornea where it will be less astigmatism-inducing. Reducing the size of the incision may help as well. Dr. MacDonald suggested modifying the MSICS using the miLOOP (Carl Zeiss Meditec) to create a 5 mm mini MSICS, a smaller incision, which can affect astigmatism.
A recent prospective study considered another factor in minimizing astigmatism in MSICS: white-to-white measurements.1
“We were trying to get a better handle on treating astigmatism,” said Robin Vann, MD, adding that when planning for small amounts of astigmatism with MSICS there were occasions where he was getting astigmatic surprises. He thought that possibly, akin to previous RK, arcuate, and limbal relaxing incisions, the closer these were to the visual axis, the greater their impact.
Dr. Vann and co-investigators found, however, that this had minimal effect. “Despite my thinking about the white-to-white, at least in small incision cataract surgery where I was trying to make my incision very close to the limbus, whether it was temporally or superotemporally, this did not have any association,” Dr. Vann said, adding that other factors such as preoperative existing astigmatism, preoperative IOP, central corneal thickness, absolute length, number of paracentesis incisions, or the axis of the main incision weren’t statistically significant either.
In this study, incisions were kept to 2.2 mm. However, in cases where they are slightly larger, astigmatism may be a factor. Dr. Vann cited a previous study2 that suggested that white-to-white diameter of the cornea did influence the surgically induced astigmatism. “In the study, they were doing their incisions superotemporally or superonasally, making 3 mm incisions,” he said. “They were operating closer to the visual axis and they were using a larger incision.” Many think that incisions under 2.5 mm tend to be relatively neutral in terms of overall impact on the cornea, Dr. Vann continued, adding that with this in mind it can be helpful to keep incisions as small as possible.
Dr. Vann said he’s now using an intraoperative aberrometer to help address astigmatism. “Typically, we’ll bring the pressure up to physiologic, so that it’s a normal 15–20 mm Hg, then we’ll take a reading of the aphakic refraction so it can tell us what the astigmatism is,” Dr. Vann said. This also takes into account the posterior cornea and the impact of the main incision that might otherwise limit success.
In Dr. MacDonald’s view, all cataract surgeons, even in developed countries, should be comfortable with small incision cataract surgery. There will likely be a time when the best choice for patient safety and quality may be small incision cataract surgery, Dr. MacDonald said. “If you don’t have confidence in that skillset, you are more likely to say, ‘I can phaco everything,’” she said, adding that the small incision technique can avoid damage to the cornea in complex cases.
To learn MSICS properly, Dr. MacDonald recommended taking a course. “It’s great to learn pearls from other surgeons who are experts in the field,” she said.
Going forward, a new technology is being developed by Carl Zeiss Meditec that will remove the nucleus without any phaco energy, which Dr. MacDonald thinks will help as well. “I think using technology that is being developed will allow us to bring small incision surgery to all who need it without fear of damaging the nucleus,” Dr. MacDonald concluded.

About the doctors

Susan MacDonald, MD
Associate Clinical Professor
Tufts University School of Medicine
Boston, Massachusetts

Robin Vann, MD
Associate Professor of Ophthalmology
Duke University
Durham, North Carolina

References

1. Zhang W, et al. Influence of corneal diameter on surgically induced astigmatism in small-
incision cataract surgery. Can J Ophthalmol. 2019;54:556–559.
2. Theodoulidou S, et al. Corneal diameter as a factor influencing corneal astigmatism after cataract surgery. Cornea. 2016;35:132–136.

Relevant disclosures

MacDonald
: Carl Zeiss Meditec, Perfect Lens
Vann: Alcon

Contact

MacDonald:
susanmacdonaldeyecorps@gmail.com
Vann: Robin.Vann@duke.edu

Optimizing manual small incision cataract surgery outcomes Optimizing manual small incision cataract surgery outcomes
Ophthalmology News - EyeWorld Magazine
283 110
220 169
,
2020-10-21T07:57:44Z
True, 10