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Labeling system will use exact refraction values on IOL package
With the new labeling, ophthalmologists may be able to reduce the amount of refractive error after cataract surgery, developers say.
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A labeling system that displays exact refraction values on IOL packages, rather than 0.5-D step values, has been developed in Germany to attempt to enhance the postoperative refractive outcome of cataract surgery.
“There was a realization that there is … the impression [among surgeons] that the tolerances/bandwidths of the 0.5-D step labeling is ±0.25 D, which is not true due to the International Organization for Standardization (ISO) manufacturing tolerances,” said Thomas Neuhann, MD, in an e-mail to OSN.
Dr. Neuhann noted that ophthalmologists have achieved consistently improving outcomes in cataract surgery with advances such as phacoemulsification, capsular bag implantation, and improved design and placement of IOLs. Manufacturers are now in a phase of quality development in which subtle factors such as IOL power labeling are being scrutinized, he said.
The German ophthalmic company Technomed has begun using the exact labeling on its EasyCare 600 IOL and is offering ophthalmologists the option to order whatever lens power they need through a special mailing service.
This development addresses the variability in IOL package labeling that allows for a degree of difference between the lens as labelled and the needs of the individual patient, according to the company.
“We realized that the associated inexactness didn’t really have to be there,” Dr. Neuhann said, speaking about the traditional labeling system.
The new labels will include both the common 0.5-D step labeling and new exact refraction values that specify the power of the lens down to 0.01 D, according to the company. This will minimize the postop refractive error associated with mismatched lens power, according to Technomed officials.
With the new labeling, the exact refraction values will result in more accurate surgical results, allowing ophthalmologists to isolate other reasons for postop refractive error, Dr. Neuhann said.
Problems with ISO standards
With standard package labeling, surgeons assumed that the power of the IOL in the package was within ±0.25 D of the labeled dioptric power, Dr. Neuhann said, when in fact the manufacturing tolerances set out by ISO are much broader. This often led to error in the final surgical outcome, he said.
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In traditional labeling, the tolerance permitted by ISO is ±0.3 D for IOLs with powers from 0 D to 15 D; ±0.4 D for powers greater than 15 D up to 25 D; ±0.5 D for powers greater than 25 D up to 30 D; and ±1 D for powers greater than 30 D, according to information provided by Technomed (Table).
The company provided an example of the difference in the possible range of error. With traditional labeling, to achieve a required refraction of 21.31 D for emmetropia, an ophthalmologist would select a lens labeled 21.5 D. But within the ISO tolerances the actual power of such a lens might be 21.9 D, resulting in a refractive mismatch of 0.59 D.
With the exact refraction value labeling, the ophthalmologist can order a lens as close as possible to the desired refractive power of 21.31 D, according to the company. Logistical factors make it unlikely that Technomed will be able to match the exact desired refraction value within 0.01 D, the company said, but the surgeon can choose the next closest value available and have it delivered the next morning.
“Technomed wanted to distinguish itself from the rest of the market by a documented effort toward the highest possible precision, at least from the technical and the ‘possibility’ side, which might be beneficial for patients in certain cases or for A-constant calculations,” Dr. Neuhann said.
For Your Information:
- Thomas Neuhann, MD, can be reached at Helene-Weber-Allee 19, Munich 80637, Germany; 49-89-159-31-339; fax: 49-89-157-8394; e-mail: prof@neuhann.de.
- Technomed can be reached at Arnold-Sommerfield-Ring 1, D-52499 Baesweiler, Germany; 49-2401-8099-0; fax: 49-2401-8099-36; e-mail: info@tmed.de.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.