Cataract
September 2021

by Liz Hillman
Editorial Co-Director

Biometry is essential for IOL power calculations, but when might you need a new biometer? What should you look for? What is there to know about this technology, how it evolved, and where it is today?

If you’re going to start talking about biometry, the first stop is Kenneth J. Hoffer, MD. Dr. Hoffer was the first ophthalmologist in the U.S. to use an ultrasound biometer to measure the axial length of the eye for IOL power calculations in 1974. In 1999, he was the first in the country to use an optical biometer and conduct a study that found optical biometry was easier and more accurate than ultrasound immersion biometry. Dr. Hoffer said he has been the first U.S. physician to use or try every optical biometer that’s been introduced in the country.

“I became the grandfather of IOL power calculations and biometry just by hanging around a long time,” Dr. Hoffer said.

Biometry history

In April 1974, Dr. Hoffer first used an ultrasound biometer to measure axial length for a lens power calculation.

“There were ophthalmologists in the United States who were doing lens implantation, but there weren’t any sophisticated calculations. They were implanting an 18 D lens in every patient’s eye. If you had a patient who was a –9 D myope, restricted by thick glasses, they’d get an implant and be a –9 D postop. Obviously, if you could adjust the lens implant power, you could get them out of glasses overall,” he said.

“After 50 years in this field, if I felt the need or had to buy a new instrument, I would make sure it was a swept-source OCT because of the technology being so much better, even though the result is about the same.”

Kenneth J. Hoffer, MD

Dr. Hoffer learned of A-scan biometers that could measure the length of the eye when he was at a course in Long Island, New York, in 1972. He said he initially laughed and wondered who would care about the length of the eye. The ophthalmologist who introduced this device, Dr. Hoffer said, had the last laugh because Dr. Hoffer called him 2 years later to ask the name of the machine, acquired one, and used the measurement for a lens power calculation for his first IOL implantation using his new Hoffer formula.

In 1999, Dr. Hoffer said he became the first ophthalmologist in the Western Hemisphere to acquire an IOLMaster 500 (Carl Zeiss Meditec), the first optical biometer. Ten years later, in 2009, he gained access to the LENSTAR LS900 (Haag-Streit). Dr. Hoffer said he now has access to every optical biometer.

When to consider a new biometer

The first reason one might want a new biometer is if it isn’t functioning properly. If it is functioning and producing accurate results, Dr. Hoffer said it’s still useful.

“If you have a biometer, whether it’s an ultrasound or optical, and it’s working properly, an ophthalmologist doesn’t need to every 5 or even 10 years turn around and buy a new biometer,” he said.

There are three things you want out of a biometer, Dr. Hoffer said: axial length, corneal power and astigmatism, and anterior chamber depth.

“There are other things you can get but those are the essentials,” he said.

If an ophthalmologist wants the latest and greatest technology—and can afford it—that’s another reason to consider a new machine. These newer options have several refinements and technological improvements that are nice to have but not essential, according to Dr. Hoffer.

H. John Shammas, MD, told EyeWorld he could think of two reasons why it might be time for an ophthalmologist to think about getting a new biometer. One scenario is in a busy cataract practice.

“It will enhance the workflow, and there will be a substantial savings in time evaluating eyes prior to surgery. The newer biometers have a much higher acquisition rate, especially in dense cataracts with less dependence on A-scan immersion biometry,” he said.

Another scenario is for the ophthalmologist who has a 10-year-old (or older) biometer.

“[I]t might make sense to acquire a new one instead of servicing an older one,” he said. “Besides upgrading to a newer technology, he/she will have access to the latest IOL power formulas.”

Jennifer Loh, MD, went through the process of researching and choosing a new biometer for her practice earlier this year. She had originally purchased an IOLMaster 500 when she opened her practice 5 years ago. At the time, she wanted an optical biometer and went with an older model, which she said worked great for years.

The biggest reason why she sought out a new biometer recently to replace her IOLMaster 500 was enhanced capabilities, such as having newer formulas programmed and being able to penetrate through denser cataracts.

What to consider in a new biometer

There are different technologies that achieve biometry measurements via different principles, such as partial coherence interferometry (PCI) or optical low-coherence reflectometry (OLCR). One of the newer options is swept-source OCT (SS-OCT). Two swept-source OCT biometers available in the U.S. are the IOLMaster 700 (Carl Zeiss Meditec) and ARGOS.

“After 50 years in this field, if I felt the need or had to buy a new instrument, I would make sure it was a swept-source OCT because of the technology being so much better, even though the result is about the same,” Dr. Hoffer said.

Dr. Shammas described swept-source OCT as “the new gold standard of biometry.” He said new swept-source biometers have simple and highly efficient interfaces for easier IOL power selection using newer formulas.

Dr. Loh ended up purchasing an ARGOS. Prior to the switch, she said her older biometer was not able to penetrate through denser cataracts and she was having to switch to traditional ultrasound A-scans, which she said was not ideal for patients who wanted premium lenses. It was not only less accurate, but her technicians weren’t as familiar using the ultrasound biometer. It was more time consuming.

In addition to the type of technology, Dr. Hoffer said one reason to consider a new biometer, and a factor to consider when selecting a biometer, is IOL power calculations. While you can find the formulas online and perform them manually, newer biometers do the calculation and provide a printout. Dr. Hoffer said the Hoffer Q, SRK/T, and Holladay 1 are the standby formulas that have been used for a long time, but some instruments have different and newer formulas.

The formulas Dr. Hoffer recommended using—either online or via the biometer, when available—are the Kane formula, the Barrett Universal II, and the new Hoffer QST, all with printouts for the chart.

“You can stick with the old formulas, but why [would you] when the new formulas are proven to provide better [outcomes],” he said.

Dr. Loh said with her older biometer, she was having to go online and manually recalculate all of her IOLs.

“I wanted to be accurate and meticulous so I would go online and type in the information. This was very time consuming, but there is also the risk for transcription errors. That’s what took me so long; I was triple checking. Here I was getting busier … and errors would have been devastating,” she said, explaining that a newer biometer with this capability would be accurate, convenient, and easy to use.

Dr. Loh said she chose ARGOS because it had great data showing accuracy and reliability but also significant support, with the company training her and her staff. When she spoke to EyeWorld, she was 2 months into using the new technology and said she and her staff were impressed with how fast it was.

“I don’t think since we’ve had it that I’ve had to do an A-scan, which is a huge relief,” she said.

She also said the technology was easy to learn. She hired two new staff members with no prior ophthalmology experience and found they were able to easily learn how to use the machine.

When it comes to considering a new biometer, Dr. Loh offered this additional advice: She said the device should show anterior chamber depth and data on the keratometry reading.

“Reliability on K readings is critical, and make sure axial length and core measurements are accurate. Also, getting through a dense cataract is important,” she said.

Dr. Shammas also said he thinks physicians should consider SS-OCT biometers when they’re seeking out new equipment, but perhaps consider one that is also a Scheimpflug tomographer.

“As cataract surgeons, we are always looking for ways to streamline our process and improve our results. The most important objective is to optimize patients’ outcomes and satisfaction after surgery. We need to have a keen eye on every step of the patient’s clinical journey, from our preoperative assessment to our surgical procedure and postoperative recovery. The trend now is to streamline the process by bringing important clinical enhancements to the operating room,” he said, explaining that improved integration of the biometry reading with intraoperative aberrometry eliminates the need for manual data entry, reducing transcription errors, and can be paired with digital marking systems for precise and integrated IOL planning and execution.

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About the physicians

Kenneth J. Hoffer, MD
Clinical Professor of Ophthalmology
Stein Eye Institute
University of California, Los Angeles
Los Angeles, California

Jennifer Loh, MD
Loh Ophthalmology Associates
Miami, Florida

H. John Shammas, MD
Clinical Professor of Ophthalmology 
Keck School of Medicine of the University of Southern California
Los Angeles, California

Relevant disclosures

Hoffer: Receives royalties for the use of the trademark name Hoffer and assuring the
accurate programming of his formulas from most all optical biometer manufacturers
Loh: None
Shammas: Alcon, Oculus

Contact

Hoffer: khoffermd@startmail.com
Loh: jenniferlohmd@gmail.com
Shammas: hshammas@aol.com