Aspheric optic lens favorable in early clinical experience

January 1, 2009

In cataract surgery cases where implantation of a monofocal acrylic IOL is planned, a recently approved model (Akreos Advanced Optics Aspheric Lens [model AO60], Bausch & Lomb) has rapidly become the IOL of choice for one surgeon who has implanted almost 100 of the lenses.

Key Points

Dallas-In cataract-refractive surgery cases where implantation of a monofocal acrylic IOL is planned, a recently approved model (Akreos Advanced Optics Aspheric Lens [model AO60], Bausch & Lomb) has become the IOL of choice for Jeffrey Whitman, MD, president and chief of surgery at Key-Whitman Eye Center, Dallas.

The model was approved by the FDA in September. Dr. Whitman said that with its combination of material and design features, this single-piece, aspheric foldable implant seems to offer everything he was looking for in an IOL for insertion through an unenlarged standard (~2.8-mm) cataract incision. From his first case, Dr. Whitman said, he was struck by the ease of the implantation procedure, and over a period of a few months, outcomes in just fewer than 100 eyes with the lens implanted attest to the ability of the lens to deliver predictable refractive results and excellent vision outcomes.

"I expect the [IOL] will rapidly become a new gold standard in monofocal acrylic IOL technology for other surgeons, and that like me, they will be anxiously awaiting FDA approval of the microincision version of this lens platform, which will be implantable through a 1.8-mm incision," Dr. Whitman told Ophthalmology Times.

The lens is constructed of a hydrophilic acrylic material that has time-tested biocompatibility and the advantage of a 26% water content so that problems with glistenings and water vacuoles associated with other acrylic materials are avoided.

"There have been a lot of reports about glistenings with hydrophobic acrylic IOLs. While usually not visually significant, they can cause problems for some patients," Dr. Whitman said. "There is no concern with the hydrophilic acrylic material of [this new model]."

The single-piece IOL also has a unique haptic design, providing four-point fixation so that once the implant is released into the capsular bag, it is self-centering and very stable.

"It is actually fun to watch how easily the [implant] positions itself within the capsular bag," he said.

Implantation advice

Dr. Whitman did, however, offer a tip for implantation: "Since the [IOL] is a fairly thin lens, it has a tendency to float up on the viscoelastic. By pointing the injector down toward the capsule and using the lens-positioning instrument through the paracentesis for added guidance, automatic positioning of the implant in the bag after it is released is enabled, so there is no need for intraocular manipulations."

The injector system itself (AI-28 inserter, Bausch & Lomb) is a disposable, single-handed system that is very easy to use and performs reliably for delivering the IOL. Modeled after the injector used for the company's silicone implants, the injector system is designed so that the surgeon need only lay the IOL in the cartridge, clip it closed, and insert the cartridge into the injector.

"There is no folding or tucking of the footplates or the haptics, so that the IOL unfolds easily once it exits the injector tip," he said. "The situation that is sometimes encountered with other one-piece acrylic IOLs where a haptic may stick to the optic of the lens won't happen with this injector system."

In cases where the [IOL] is being implanted, Dr. Whitman recommended a capsulorhexis of 5.5 to 6 mm in diameter, which will prevent trapping of viscoelastic behind the IOL while also making cataract removal easier. He is using an A-constant of 118.4 and the SRK-T formula with his optical biometer (IOLMaster, Carl Zeiss Meditec) for power calculation. With this approach, he said he has not encountered any refractive surprises and has had excellent visual acuity results.

Visual outcomes

"Although the average cataract surgery patient has positive spherical aberration in the cornea, there are exceptions in the eye that has not undergone surgery and in some patients who have had previous hyperopic keratorefractive surgery," he said. "The [implant] is spherical aberration neutral and so there is no need to be concerned about the consequences of adding negative or positive spherical aberration.

"Leaving the average patient with a small amount of positive spherical aberration may actually be beneficial for enhancing depth of field and providing some pseudoaccommodation," Dr. Whitman added.

PCO

To date, his longest duration of post-implantation follow-up is only 2 months, he said. Although that amount of time is too soon to report on the risk of posterior capsule opacification (PCO) in his own series, considering the material and design features of the lens combined with existing longer experience in Europe, PCO is not expected to be much of a problem, Dr. Whitman said.

"This hydrophilic acrylic material has excellent biocompatibility, and the implant is designed with a 360° square edge around the posterior aspect to prevent lens epithelial migration and PCO," he concluded.

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