March 2020

IN FOCUS

Illuminating intraoperative technologies
Intraoperative aberrometry’s role in guiding IOL decisions


by Vanessa Caceres Contributing Writer


View from the ORA (Alcon) as seen in the surgeon’s right ocular of the microscope
Source: Samuel Masket, MD

 

With increasing precision in IOL calculation formulas, surgeons may wonder if there is still a role for intraoperative aberrometry. Those currently using the technology say it is helpful, especially in certain patients.
“I think there’s a nice role for aberrometry to confirm or modify IOL power. It still has a place,” said Douglas Koch, MD.
The key is knowing when to use it.

Best uses of aberrometry

There are several ideal scenarios for intraoperative aberrometry. One of those is when trying to achieve a specific refractive target. “It’s ideal for toric and multifocal lenses and in patients with prior refractive surgery,” said John Berdahl, MD.
Among toric IOL patients, many surgeons will use intraoperative aberrometry for IOL orientation and alignment. “They think it does the best job of aligning the posterior and anterior cornea,” said Dr. Koch, who previously introduced the importance of posterior cornea measurements.
Intraoperative aberrometry is useful in post-refractive surgery eyes because it can be harder to achieve accuracy with this patient group. However, it’s important to consider the type of surgery a patient had. “Although it can be helpful in radial keratotomy patients, they can have significant fluctuations,” Dr. Berdahl said. “It’s not necessarily unhelpful, but that needs to be taken into account with the full picture.”
Another use for intraoperative aberrometry is to confirm what you may already have in mind for IOL power. “Using it decreases errors from inadvertently implanting the wrong IOL due to clerical errors,” said Bonnie Henderson, MD.
Dr. Koch shared the example of a patient of his who needed an IOL exchange and had a toric IOL. Using the website AstigmatismFix.com, Dr. Koch didn’t get the IOL choice that he expected. “At the time of surgery, I used intraoperative aberrometry, and it pointed me in the direction I thought it would logically go. We got a great result,” he said.
He also shared a scenario in which wrong data were uploaded onto the website he usually uses for IOL calculations. However, with aberrometry, he was able to catch that and identify an appropriate IOL power.
In addition to these common uses, Dr. Henderson has found several other reasons to choose intraoperative aberrometry, including with irregular corneal pathology (such as scarring) where measurements may not be accurate, cases of macular pathology or staphylomas, and eyes with long or short axial lengths.
“In my practice, intraoperative aberrometry has replaced the use of immersion A-scan in many of these unusual eyes,” she said.

Calculation changes

Just how often does the use of aberrometry change the IOLs that surgeons might use?
For Dr. Berdahl, it will change his choice of a toric lens about 30% of the time. In post-refractive cases, it changes his decision about 20–30% of the time. For standard eyes with no special needs or pathology, it only changes his choice about 5% of the time; these are not eyes that typically benefit from aberrometry, Dr. Berdahl added.
For Dr. Koch, the use of aberrometry changes his choice in post-LASIK eyes about 25% of the time. However, he pointed out that he and his colleagues do a lot of research on preop measurements, so he has two biometers used before surgery. Additionally, they do many more preop calculations, beyond what other surgeons typically do.

Considering the latest IOL formulas

Despite these potential benefits from using intraoperative aberrometry, there still is the question of its value when there are newer IOL power calculation formulas, such as the Hill-RBF and Barrett Universal II formulas, known for their high level of accuracy.
“As these formulas have improved, there’s less of a benefit to intraoperative aberrometry in standard cases, but the benefit is still meaningful in toric lenses and post-refractive cases,” Dr. Berdahl said.
“As good as these newer formulas are, intraoperative aberrometry is still better than an IOL formula alone,” Dr. Henderson said, adding that the change in IOL power made by many surgeons using intraoperative aberrometry has led to an improvement in their outcomes.
Dr. Koch thinks the role of aberrometry will diminish as formulas continue to improve, but the end result is situation- and surgeon-specific. “It depends on how many measurements a surgeon gets. If it’s just one biometer measurement, then [the results] from intraoperative aberrometry could be a lifesaver,” he said.

Refining your use for better results

If you’re using aberrometry, keep in mind that there are a few factors that can adversely alter the readings. These include:
• The lid speculum
• Trauma to the epithelium
• Corneal edema
• Not filling the eye with the appropriate ophthalmic viscosurgical device (OVD)
• A dry corneal surface
• Poor patient focusing
• A low or high IOP
• The wrong input of preop data
• Scars
To help avoid these factors and to improve your aberrometry results, here are a few clinical pearls:
1. Protect the corneal epithelium. Start as soon as the patient is in the ASC and until the time of measurement, Dr. Koch advised.
2. Keep the cornea protected with OVD or with frequent irrigation. A cohesive OVD should be used to fill the eye rather than a dispersive OVD or a hybrid OVD with a high molecular weight, Dr. Henderson said.
3. Make sure the patient is looking directly at the fixation light. Ask him or her to tell you when that light goes out. “That helps guarantee that they are looking in the correct direction,” Dr. Koch said.
4. Use the personalized outcomes to help guide decisions. Dr. Berdahl finds the numbers that are particular to his surgical outcomes more useful than global outcomes. “With time, you get a sense of when you should trust [the numbers] more and when you shouldn’t,” he said.

At a glance

• Intraoperative aberrometry can help guide a surgeon’s IOL choices.
• This type of technology is valuable in eyes that have had refractive surgery or those receiving toric IOLs.
• The use of newer IOL formulas may change or lessen the role of aberrometry.
• Appropriate hydration and fixation can help improve results.

About the doctors

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

Bonnie Henderson, MD
Clinical professor
Tufts University School of Medicine
Boston, Massachusetts

Douglas Koch, MD
Professor and Allen, Mosbacher, and Law Chair in Ophthalmology
Baylor College of Medicine
Houston, Texas

Relevant disclosures

Berdahl
: Alcon
Henderson: Alcon
Koch: Alcon, Carl Zeiss Meditec, Johnson & Johnson Vision

Contact

Berdahl
: john.berdahl@vancethompsonvision.com
Henderson: bahenderson@eyeboston.com
Koch: dkoch@bcm.edu

Intraoperative aberrometry’s role in guiding IOL decisions Intraoperative aberrometry’s role in guiding IOL decisions
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