Intraoperative refractive guidance systems

Cataract
December 2021

by Liz Hillman
Editorial Co-Director

Intraoperative refractive guidance systems is a term coined by Kevin M. Miller, MD, describing the technology offered to patients as an additional, out-of-pocket benefit for their cataract surgeries. 

Dr. Miller said within this class of technologies are systems that give surgeons guidance on refractive issues during the case, including spherical power, cylinder power and alignment, and more. He said that using the term “intraoperative refractive guidance” is a communication aid with patients. 

“Patients don’t need to know which device or combination of devices we’re using. They just want to know we’re using the latest technology to give them the best chance at a good refractive result,” he said.

Intraoperative aberrometry

ORA (Alcon) is currently the only intraoperative aberrometry unit on the market in the U.S. It is used after a cataract is removed to confirm (or in some cases alter) IOL selection and placement. 

“Roughly two-thirds of the time, ORA is going to tell you the lens you should be putting in is the lens you planned on putting in. So two-thirds of the time, it provides no benefit other than a check that we have alignment of the stars,” Dr. Miller said. “Then there is the other third of the time when it tells you to do something you weren’t planning to do—go up or down on the power of the sphere, the cylinder, or both.”

“Patients don’t need to know which device or combination of devices we’re using. They just want to know we’re using the latest technology to give them the best chance at a good refractive result.”

Kevin M. Miller, MD

How does a surgeon decide to change course based on what ORA is telling them? Dr. Miller said there are three scenarios: 1) Ignore ORA and do what you were originally planning. 2) Do something between what you were planning and what ORA tells you to do. 3) Change course and go with ORA’s recommendation. 

Dr. Miller said you have to do your own data analysis, but based on his outcomes, he’s learned that his outcomes are about 7% better by one metric than if he didn’t use ORA. This means that he’s doing well without ORA but that it does make him a little better, Dr. Miller said. 

Is it worth the expense and extra time, knowing that it won’t make every case better and could, in some cases, make outcomes worse if its recommendations are followed? That’s the dilemma, Dr. Miller said.  

Carlos Martinez, MD, said he’s learned which cases to favor ORA vs. preop data. Cases he’ll favor include post-refractive surgery cases, astigmatism management cases, and those with irregular corneas.

“I use ORA in advanced technology lens cases and find it incredibly useful, especially in post-refractive cases and astigmatism management cases. My post-RK and post-LASIK measurements are right on the dot. They both have a standard deviation of error as a regular lens thanks to ORA,” he said.

When ORA is not in agreement with preop measurements, Dr. Martinez said he’ll go back to his data and look for outliers. 

“Most of the time, I can see a cluster. Occasionally, IOLMaster [Carl Zeiss Meditec] is off as to the amount of the magnitude of astigmatism or even power. In addition, sometimes technicians forget to look at the quality of keratometry readings on the IOLMaster,” he said. “I compare my IOLMaster measurements to my ORA measurements. If they agree, I don’t do anything else. I have a higher level of confidence that I have the right power, axis, and alignment. ORA helps me decide what numbers are within a cluster and which numbers are outliers. When there is no agreement, I use my ORA measurements. In post-refractive patients, I mostly use ORA.”

Dr. Miller gave two examples where ORA recently helped improve his outcomes. The first was a patient who had post-myopic LASIK, with a correction of about –7 D or –8 D. He said he’s comfortable with his post-LASIK IOL power calculations, so he was confident in the lens power he had selected. When he used ORA during the case, however, it was telling him to go 2 D away from his original plan. He said he repeated the measurements multiple times and kept getting the same ORA result. 

“I didn’t want to ignore the ORA completely, so … I ended up going a half a diopter toward what ORA told me to do. On postop day 1, the patient was 20/20 –1 or –2. … If I had followed my original plan, I would have been off,” he said. 

Another case involved a patient slotted to receive a toric lens. This patient had a heavy brow, he was squeezing, oozing lipid all over the tear film, and he wasn’t focusing well on the aberrometer. All in all, it was not a good ORA case. 

“When you don’t have a good tear film and good exposure, you have to be careful about the ORA results,” Dr. Miller said. 

Intraoperative aberrometry eventually told Dr. Miller to rotate the lens 90 degrees away from where he had originally intended. Dr. Miller didn’t trust this advice and decided to leave the lens at his originally planned axis. He finished the case, pulled off the drapes, and was about to send the patient to recovery when his resident pulled up the topography; the left eye axis said 147, not 56 as was inputted in the plan. “We had input the right eye numbers for the left eye,” Dr. Miller said. 

He reran the calculations with the patient lying on the table, reprepped him, redraped, and rotated the lens 90 degrees. Upon repeating the aberrometry, it said no rotation recommended. “The next day the patient was 20/20 +2 and happy as a clam. ORA didn’t save me, it was the resident, but ORA was trying to save me and I was ignoring it,” Dr. Miller said. “ORA raised a red flag and it got pursued.”

Bryan S. Lee, MD, JD, uses ORA for LRIs, toric IOLs, and presbyopia-correcting IOLs. He also offers it as a standalone for patients with post-refractive eyes who choose a standard monofocal instead of the Light Adjustable Lens (RxSight). 

“Aberrometry is helpful as a tiebreaker between different power IOLs. I use it that way and almost never change by more than one increment for either spherical or cylindrical power,” he said. “It is nice to have aberrometry for these tiebreakers, although the better feeling is when the preoperative and intraoperative data are consistent. There are certain eyes, such as very short eyes, where aberrometry is less accurate, but these are the hardest eyes for the IOL formulas as well.”

Image guidance

Image guidance systems can eliminate the need to manually mark an eye for toric lens placement, Dr. Miller said. Technologies that can achieve this are the VERION Image Guided System (Alcon), CALLISTO Eye (Carl Zeiss Meditec), and the NGENUITY 3D Visualization System (Alcon). 

When patients lie down, the eye rotates, necessitating the need for manual marking or the use of such image guidance systems to align toric lenses. Manual marking is low tech and relies on the physician’s judgment. Image guidance systems, like VERION and CALLISTO, Dr. Miller said, take a picture of the eye that is then used as a reference in the OR. 

“What CALLISTO and VERION do is show us where to make the phaco incision, where to make the relaxing incisions, and how to align a toric lens in the eye, without ever having to mark the eye,” he said.

With VERION, for example, Dr. Miller said a picture of the eye is taken at the same time as the keratometry readings, with the K readings locked to the reference image. In the operating room, VERION allows the physician to do alignment under the LenSx Laser (Alcon) for incisions exactly where the physician planned them or under an operating microscope with an overlay of incisions or toric alignment in a heads-down display.

Dr. Martinez said he uses the coordinate system on VERION in the OR and moves his scope until ORA and VERION agree. Doing this, he said, helps him know exactly where the steep axis is and compare the ORA axis measured in a recumbent position to the axis of the preoperative data obtained in an upright position. He also uses the capsulorhexis function on VERION.

“Sometimes I would do a beautiful surgery and my capsulorhexis would be a little wide in one place. It would sit against the edge of the lens and move the lens a little as it contracted. That no longer happens [with VERION],” he said. “I use my capsulorhexis overlay and I can overlap the lens perfectly. … I know where the visual axis is, I know where to center my capsulorhexis, and I know how big to make it. It makes it quite predictable.”

Dr. Lee said he finds digital marking helpful because the cornea can change intraoperatively, reducing the accuracy of aberrometry.

“[B]eing able to line the treatment up with the preoperatively determined axis is more accurate and more efficient than manual marking,” he said. “However, the Light Adjustable Lens changes this entire paradigm because you don’t have to worry about alignment, rotation, or imperfections in IOL calculations.”

Dr. Miller described CALLISTO as similar to VERION, but he noted that you have to use the suite of Carl Zeiss Meditec products with it. 

Overall, Dr. Miller said using image guidance “takes a lot of extra time and planning. … It’s faster to manually mark.” But he said using these technologies is more accurate. He thinks the results with manual marking are good, but intraoperative guidance is the way things are going. 

NGENUITY can perform many of the same functions as VERION and CALLISTO (and provides the surgeon additional information) in a heads-up display. Dr. Miller finds the ergonomics of NGENUITY awkward, with the camera attached to the microscope in front of the surgeon and the monitor off to the side. “You want to look straight ahead, but you have to watch a television screen 30 degrees to your left,” Dr. Miller said. Despite the ergonomic challenge, he said he thinks digital microscopy is the way of the future. 

Take-home messages

Dr. Martinez said his biggest message is for physicians to understand that when there is cyclotorsion of the eye, it is difficult to compare preop measurements taken when the patient was sitting to intraoperative measurements lying down.

“Realigning ORA to VERION is huge. … It makes the delivery of astigmatism correction much easier and more predictable,” he said. 

Dr. Miller said he thinks there is a benefit to these technologies but acknowledged they are still in their infancy and they do take time. 

“If you wanted to bang out cases, this is not for you because it will take time for you to get used to and there are a lot of little tricks you have to learn to make this work,” he said. 

Dr. Miller noted that patients like the technologies and said he has had no problem with them signing up for intraoperative refractive guidance, even though there is an extra cost associated with it. 

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What about intraoperative OCT?

None of the physicians EyeWorld spoke with used intraoperative OCT in cataract or anterior segment surgery in general. All understood the utility it would have for posterior segment procedures, but Dr. Miller said it doesn’t add anything to his anterior segment practice. He played with an intraoperative OCT device and said it can help determine if there is good attachment of an endothelial graft to the back of the cornea. He didn’t find it necessary for that though, and he couldn’t justify the expense of the machine for this use.


About the physicians 

Bryan S. Lee, MD, JD
Altos Eye Physicians
Los Altos, California

Kevin M. Miller, MD
Kolokotrones Chair in Ophthalmology
David Geffen School of Medicine
University of California, Los Angeles
Los Angeles, California 

Carlos Martinez, MD
Eye Physicians of Long Beach
Long Beach, California

Relevant disclosures

Lee: Carl Zeiss Meditec
Miller: Alcon
Martinez: Alcon

Contact 

Lee: bryanslee@gmail.com
Miller: kmiller@ucla.edu
Martinez: drmartinez@eplb.com