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Up Front | Oct 2007

Aspheric IOL Guide

Herein is a sampling of aspheric lenses available on the market.

Acri.LISA (Acri.Tec GmbH, Hennigsdorf, Germany)
LISA is an acronym for (L) light intensity distribution 65% far and 35% near; (I) independent from pupil size; (S) smooth refractive/diffractive surface profile; and (A) optimized aspheric optic.

The smooth steps of the Acri.LISA's optical principle help reduce disturbing light phenomena. The bifocal lens offers reduced glare and improved contrast sensitivity as well as good near, intermediate, and distance vision.

With an A-constant of 117.8, this monobloc hydrophilic lens has a hydrophobic surface treatment. The Acri.LISA is injected through a 1.8- to 2.2-mm incision and reduces scattered light and halos.

Tecnis (Advanced Medical Optics, Inc., Santa Ana, California)
The Tecnis aspheric IOL has -0.27 µm of spherical aberration to compensate for the spherical aberration on the cornea, thereby providing a better image contrast and improving vision in low light situations, such as night driving.

Available in a range of 5.00 to 34.00 D, the diffractive pattern of the Tecnis is placed on the posterior surface of the lens, and the prolate anterior face suppresses Z4 spherical aberration. The Tecnis adds 4.00 D at the lens plane and 2.80 D at the spectacle plane, with an A-constant of 119.1. This silicone IOL has high stability, as the polyvinylidene (PVDF) haptics are C-shaped. It is implanted through a 2.8-mm incision.

Restor and AcrySof IQ (Alcon Laboratories, Inc., Fort Worth, Texas)
The Restor aspheric IOL is injected through a 2.2-mm incision. It has 12 diffractive zones, covering the central 3.6-mm anterior lens surface. Restor is available in 18.00 to 25.00 D, and the A-constant is 118.2 for ultrasound contact biometry and 118.4 for optical biometry. The lens adds 4.00 D at the lens plane and 3.20 D at the spectacle plane. Using apodization, this lens has been shown to allocate appropriate light energy to light levels and minimize photic phenomena. As the pupil constricts, the Restor equilibrates light energy for either near or distant vision. When the pupil dilates, the lens catches less incident light to defocus the near image.

In addition to the three-piece lens, Restor is also available as a monobloc with a blue-blocker filter.

The AcrySof IQ has a low rate of posterior capsular opacification (PCO). Additionally, the slow and controlled unfolding of this lens during its implantation makes it ideal for eyes with small compromises in the capsular bag (eg, a limited central defect).

The AcrySof IQ lens is more than 9% thinner than the regular AcrySof single-piece and Natural platforms (Alcon Laboratories, Inc.), which makes it possible to implant it through 2.5-mm incisions or less.

The aspheric optic of the AcrySof IQ lens provides -0.20 µm of spherical aberration. With larger pupils, this correction enhances image quality by counteracting the remaining positive spherical aberration of the cornea.

The AcrySof IQ has a 118.7 A-constant and a modified L-haptic. The lens is available in a range of 6.00 to 30.00 D, in 0.50 D increments.

SofPort AO (Bausch & Lomb, Rochester, New York)
The SofPort Advanced Optics (AO) lens was designed with prolate aspheric surfaces so that it is free of spherical aberration and immune to the adverse effects of decentration. Optical performance is unaffected by decentration and pupil size, due to uniform center-to-edge power. With zero spherical aberration and 360º anterior/posterior square-edge optic, cell migration is minimized, and PCO rates are equal to those of acrylic lenses.

This lens has an A-constant of 118.0, and ranges from 0.00 to 4.00 D in whole diopters, and 5.00 to 30.00 D, in half diopters. This lens absorbs UV light, and includes a blue-extruded PPMA, modified C-loop, 5º haptic.

XL Stabi ZO and Invent ZO (Carl Zeiss Meditec AG, Jena, Germany)
Both Zeiss Optic (ZO) lenses offer different geometries for a larger flexibility of implantation. To optimize the contact surface with the equator of the capsular bag, as well as secure postoperative stability, the XL Stabi ZO and Invent ZO feature a three- and four-haptics design, respectively. The flexible haptics are optimized to fit bag retraction and secure long-term centration.

The Invent ZO features a posterior aspheric optic for the correction of most corneal spherical aberrations. Manufactured with hydrophilic acrylic (28%), this lens has a 0º haptic angulation and an A-constant of 118.1. Implanted into the capsular bag, the lens power ranges from 14.00 to 30.00 D. The IOL has square edges and filters UV light.

The XL Stabi ZO includes the same aforementioned components of the Invent ZO, however, the haptic angulation is 10º.

Both IOLs feature markers to identify the correct side of implantation for proper positioning during surgery.

Quatrix Aspheric (Corneal Laboratories, La Rochelle, France)
This single-piece hydrophilic acrylic IOL is an 11-mm, 360º, square-edged IOL with a 6-mm optic and 6º haptic angulation. This range of aspheric IOLs varies between 10.00 and 30.00 D for an A-constant estimated at 119.6. Viscoinjection allows the implant to travel down the corneal tunnel and be inserted through a 2.2-mm incision.

Microcryl MC X11 ASP (HumanOptics AG, Erlangen, Germany)
This lens is a foldable monobloc posterior chamber IOL with an aspheric posterior surface. It is made of hydrophilic acrylic with a UV inhibitor. The estimated A-constant is 118.3. It is recommended for patients with additional high myopia or hyperopia to achieve improved functional vision and reduced glare sensitivity.

The MC X11 ASP was developed to give patients the best image quality, as expressed by the point spread function (PSF). There is higher focal light point density with aspherics, better image quality, and a PSF closer to one. According to HumanOptics literature, spherical IOLs do not even reach PSF values of 0.1.

The lens has a sharp-edge design and can be implanted through a small incision (sub–2.5-mm) with the Medicel Viscoject Injector (Medicel AG, Wolfhalden, Switzerland) and 2.2 cartridge set. The lens is easy to fold, safe to implant, and there is less glare in the case of larger pupils. An added advantage is a more than 6 mm diameter, which is suitable for surgeons in case of potential interventions in the ocular fundus.

Softec HD (Lenstec Inc., St. Petersburg, Florida)
This high-definition microincision aspheric IOL with precision diopters comes in 0.25 D increments from 18.00 to 25.00 D; 0.50 D increments ranging from 10.50 to 29.50 D; and whole diopters increments from 5.00 to 36.00 D. With a 5.75-mm optic, the equal conic biaspheric optic is 12 mm in length. The modified C-haptic has a 0º angulation and an A-constant of 118.

CeeOn Edge (Pharmacia Corp., Peapack, New Jersey)
The US Food and Drug Administration (FDA)-approved CeeOn Edge silicone IOL has a refractive index of 1.46, a 6-mm optic with 6º of haptic angulation, and a Cap C design. The square-edge design of the lens helps to reduce PCO rates and a medium refractive silicone combined with an equibiconvex curvature results in less glare and visual distortions.

The overall length of CeeOn Edge is 12 mm, and the dioptric range is from 5.00 to 30.00 D.

C-flex Aspheric and Superflex Aspheric (Rayner Intraocular Lenses,
East Sussex, UK)
The Rayner C-flex Aspheric and Superflex Aspheric IOLs include the Amon-Apple Enhanced Square Edge for low PCO rates, antivaulting technology for optimal centration, and a single-use soft-tipped injector capable of insertion through a sub–3-mm incision.

The C-flex Aspheric has an optic body diameter of 5.75 mm and an overall length of 12 mm. The estimated A-constant is 118, and the dioptric range spans from 18.00 to 29.50 D in 0.50 D increments and 30.00 to 34.00 D in 1.00 D increments.

The Superflex Aspheric has an optic body diameter of 6.25 mm and an overall length of 12.5 mm. The estimated A-constant is 118, and the dioptric range spans from -10.00 to 22.00 D in 0.50 D increments.

Afinity Collamer Aspheric IOL (STAAR Surgical, Monrovia, California)
Made from a highly biocompatible collagen-copolymer mix, the Afinity Collamer Apsheric IOL was designed to perform optimally, even in a decentered or tilted position. The 6-mm equiconvex aspheric lens is 13 mm long and has modified C-loop 5º angulation haptics. Correction ranges from 10.50 to 30.50 D with a suggested A-constant of 118, and the anterior depth is 5.20 mm.

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