Researchers: source of Hydroview IOL calcification found

Silicone from the packaging gasket caused clouding of the foldable lens.

Issue: November 15, 2001

ByDavid Schonfeld

ROCHESTER, N.Y. — Silicone from the Surefold packaging of the Hydroview IOL (Bausch & Lomb) has been identified as the root cause of calcification in a small number of the lenses, according to researchers at the company.

The Hydroview acrylic IOL has been available in international markets without interruption since 1995. Hydroview was approved for market release by the FDA in 1999, but the company delayed introduction of the product to the U.S. market while investigating a small number of reports of clouding or haze attributed to calcification of the lens optic that occurred in only 34 of 3,500 sites. Calcification was reported in 368 cases (0.06%), with 157 of these or 0.03% resulting in decreased visual acuity and explantation.

“In 1997, a package change was implemented in which the lens holder also became the lens folder,” said Brian Levy, OD, vice president of medical and clinical affairs. “These are hydrophilic lenses that are folded and placed into the capsular bag. The packaging change facilitated more effective implantation, and it was called the Surefold system.”

According to Dr. Levy, between 600,000 and 700,000 Hydroview IOLs have been implanted since the change of packaging, while 190,000 had been implanted with the original packaging.

“We started to hear reports of clouding and fogginess in the implanted lenses in 1999,” he said. “In some cases, this led to reduction of visual acuity to the extent the lenses were explanted. YAG laser and normal procedures used to clear the capsule were not effective in dealing with the clouding. Once we had some explanted lenses, they were sent for chemical analysis to determine the nature of the clouding phenomenon. We deduced that there was calcium on the lens surface.”

Tracking the problem

According to George Grobe III, PhD, director of materials and surface science for Bausch & Lomb, the Hydroview lens underwent extensive testing to identify the cause of the calcifications.

“Initially, when we examined the lenses, we used infrared spectroscopy,” he said. “We got an IR spectrum, we compared it to the library and got back a calcium hydroxyapatite or something close to that structure. We immediately tried another technique to look at the surface called x-ray photoelectron spectroscopy. This test provides an elemental content of the surface. Curiously, the surface was composed primarily of carbon with very little calcium — in fact, 1% or 2% calcium, which really confounded us.”

A third instrument, called a time-of-flight secondary ion mass spectrometer, was used to take a mass spectrum of the surface.

“This told us there was lipid on the top layer of this calcified material,” Dr. Grobe said. “The next step was to use the XPS and drill through the material, and we found that calcium and phosphorous were co-deposited in a phosphate-like form. There was intermittent signal from silicone and in some of the implants there was an intermittent signal from fluorine.”

Calcification from new packaging

According to Dr. Levy, calcification on the Hydroview IOL only began to occur once the packaging was changed to a silicone gasket.

“Going back, it became pretty clear that once we changed the package, calcification started to become an issue in specific sites around the world,” he said. “It is also important to note that this was not a homogeneous occurrence. In other words, it occurred at higher rates at certain sites around the world, while in the majority of sites there were no cases at all. We suspected the packaging was related to the phenomenon, but there appeared to be some clinical factors as well. The first hint we had that it was the package was the clear difference between the two groups that were implanted. There are no cases of calcification in the lenses implanted prior to the original packaging change.”

According to Dr. Grobe, when compared side by side, the difference between the two types of Hydroview lens was very small.

“We’re talking a few atom percent over the first few atomic layers of the material,” he said. “We were seeing intermittent signals from silicon in the form of a silicone. We immediately tried to figure out where the silicone was coming from, and we were able to deduce that the gasket used in the Surefold system package was actually getting on the lens through the holder-folder system.”

The researchers took their queries to George Nancollas, PhD, a calcification expert at the State University of New York at Buffalo.

“They basically set up a cell that’s ready to deposit hydroxyapatite if the surface of the material is predisposed to it forming,” Dr. Grobe said. “We had him take the older lenses in the original packaging and the Surefold lenses and put them in side-by-side cells and found that nothing happened, and we didn’t understand why.

“We then got the data back on the explants and realized there was a lipid from the patients that was on the lens surface as well. So we had Dr. Nancollas add lipid to both types of lenses and then reintroduce them into his model. We consistently saw in his model the Surefold lenses calcify and the original package lenses did not calcify, Dr. Grobe said.

One question that arose during the trial was why calcification did not occur in IOLs made of silicone.

“We stuck silicone lenses into the model and added lipid to those as well. What we saw was that eight times out of 10 the lenses did not calcify. The lipid did not remain on the surface of the silicone lenses. It actually absorbed into the lens and only remained on the surface of the Hydroview because it’s a hydrophilic lens. It set up what looks like a nice bi-layer system. Bausch & Lomb has removed the silicone gasket from the Surefold packaging system and will monitor production specimens to vigorously avoid future silicone contamination of this product,” Dr. Grobe said.

For Your Information:

Brian Levy, OD, and George Grobe III, PhD, can be reached at 1400 N. Goodman St., Rochester, NY 14603; (716) 338-5144; fax: (716) 338-0273; e-mail: blevy@bausch.com. Drs. Levy and Grobe are both employees of Bausch & Lomb.

Bausch & Lomb can be reached at 555 West Arrow Hwy., Claremont, CA 91711; (800) 423-1871; fax: (909) 399-1525.