Newer one-piece IOL offers excellent visual acuity, says surgeon

November 1, 2008

The state-of-the-art material and design of a novel one-piece IOL can offer refractive stability and predictability, according to Daniel A. Black, MBBS, FRACO, FRACS. This newer IOL rivals other more established IOLs and may soon become the gold-standard treatment in cataract procedures, he said.

Key Points

"Achieving a refractive stability and predictability with IOLs is one of the central issues in choosing a lens in cataract surgery," Dr. Black said. "In my work with the . . . one-piece IOL thus far, I have found that the lens delivers, in terms of the accuracy of a constant refractive predictability, much more so than any other one-piece IOL."

Unpredictability and changes in the refraction postoperatively can be the result of the IOL sitting a little forward or a little further back in the capsular bag, he noted. This one-piece lens particularly is novel in its design at the haptic-optic junction, because it preserves 360° protection against posterior capsular opacification. Further, the way the lens is vaulted on the haptic and its position in the capsular bag leads to its predictability and, therefore, reproducible results.

In the procedures, he has used lenses in a range from +16 to +25 D. The largest absolute error seen to date was measured at 0.68 D, and the average error was 0.27 D, with a standard deviation of 0.33 D.

"All of the results have been very encouraging so far, because we have not had anyone with more than 0.66 D, which is very good considering that with the previous one-piece lens that I have tried, I have had errors of greater than 1.75 D," Dr. Black said.

A look at some advantages

One of the major advantages of the newer one-piece IOL design is that it allows for smaller incision size because of the compressive nature of the lens material. Dr. Black said he has achieved an incision size as small as 2.3 mm using a wound-assisted technique, which he said is significantly smaller than the 2.8-mm incision size he used with a three-piece lens.

According to Dr. Black, one of the big advantages of a three-piece lens is that it provides very good long-term posterior capsule clarity. The lens has proven itself in that respect over the last 10 years, he said, adding that the potential disadvantage of the one-piece lens is that it still has to prove itself over time. Although the newer lens design may not provide or maintain that same degree of posterior capsule clarity, and possibly not for the long term as seen with the three-piece IOL, he said that patience is warranted.

Dr. Black said he is hopeful and believes that the one-piece IOL eventually may become a gold-standard treatment. The IOL is made of a hydrophobic acrylic material that has been around for at least 2 decades, and it has proven itself to be a very reliable material inside the eye, he said.

"There is always a contradiction in the expectations for the new and cutting-edge technology," he said. "We demand the newest and latest technology, but at the same time, we also want technology that is going to be proven, long lasting, reliable, etc. The only way to get there is for these brand-new technologies to stand the test of time. The one-piece lens manages to solve and resolve those competing interests well because [of its] regard to modern technology."

In terms of leading the way in technologic advancements, the one-piece IOL was the first lens to have an aspheric anterior surface on the lens designed to correct and minimize aberration, Dr. Black said.

Further, the design of the material of the lens reduces chromatic aberration, which, in turn, enhances the quality of images, he added.

"The [one-piece] IOL is capable of passing through a smaller incision when compared [with] many other lenses, underscoring its significant and unique flexibility and pliability," he said. "Many cataract surgeons are now moving to cataract extraction through a 2.2-mm or smaller wound, and now we have a lens that is capable of going through such a similar-sized incision, because the [one-piece] IOL passes through a 2.3-mm incision."

The quality of vision following cataract surgery primarily is determined by the choice of lens implant used rather than by the surgical technique or incision size. According to Dr. Black, the one-piece IOL delivers because it has the best of modern design combined with the reassurance of a proven material for its longevity.

"It gives me great confidence to know that if I put this lens in the eye, I am going to get a good-quality, . . . predictable, and . . . long-term result," Dr. Black said.

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