In the June 2009 issue of Optometric Management, optometrist Justin Holt, OD, updates his colleagues on the latest premium IOLs available for patients who need cataract surgery or who desire lens-based refractive surgery, such as refractive lens exchange (RLE) or phakic IOL implantation.

The blending of cataract and refractive surgery

According to Dr. Holt, today’s cataract patients are also refractive surgery patients: They typically want as much freedom from glasses as possible after surgery, with the least amount of visual side effects.

He says while there is no single “perfect” IOL, people today have more options in premium lens implants than ever before, and it’s up to eye doctors to help their patients choose the IOL that best suits their needs.

Among the choices available…

Aspheric IOLs

Aspheric IOLs change in shape from the center of the lens to the periphery, a feature that is designed to sharpen vision and reduce an optical defect called spherical aberration.

Aspheric IOLs produce sharper vision than conventional IOLs, especially in low light conditions, according to manufacturers of the lenses.

Most aspheric lenses are monofocal (single power) lenses, so reading glasses typically are still needed after surgery, unless the lenses are implanted in both eyes to create a monovision correction (one eye corrected for distance vision and the other eye for near).

Also, aspheric lenses do not correct astigmatism. So eyeglasses or a second surgical procedure, such as limbal relaxing incisions (LRI), LASIK, LASEK, Epi-LASIK or PRK may be needed after surgery for patients with pre-existing astigmatism.

Examples of aspheric IOLs include:

• AcrySof SN60WF (Alcon)
• SofPort Advanced Optics (Bausch & Lomb)
• Tecnis Z9000 (Abbott Medical Optics)

Toric IOLs

Toric IOLs are premium intraocular lenses that contain both a spherical power (to correct nearsightedness or farsightedness) and a cylindrical power, which makes one meridian of the lens more curved than any other, to correct astigmatism.

Computer-applied markings on toric IOLs allow cataract surgeons and refractive surgeons to rotate the lens into the proper position within the eye so it is aligned perfectly to correct corneal astigmatism.

Toric IOLs can correct mild and moderate pre-existing astigmatism without the need for LRI or additional refractive surgery. Reading glasses may still be needed after surgery, however, unless lenses are implanted in both eyes for monovision.

The AcrySof Toric IOL (Alcon) is an example of a toric intraocular lens.

Presbyopia-correcting IOLs

Presbyopia-correcting IOLs are premium intraocular lenses that reduce the need for reading glasses after cataract or refractive surgery.

There are two types of  IOLs that correct presbyopia: accommodating IOLs and multifocal IOLs.

Accommodating IOLs

Accommodating IOLs are monofocal intraocular lenses that have a flexible surrounding structure (the “haptic”) that allows the central portion of the lens (the “optic”) to move slightly forward within the eye in response to focusing effort, thereby improving near vision.

The Crystalens IOLs (Bausch & Lomb) currently are the only FDA-approved accommodating IOLs used in the United States.

Multifocal IOLs

Multifocal IOLs, like multifocal or bifocal contact lenses, contain more than one power to correct vision at multiple distances simultaneously.

While the multiple refracting zones of multifocal IOLs provide a wider range of vision than conventional monofocal IOLs, they also cause some light scatter, which initially may cause visual symptoms such as halos at night, Dr. Holt says.

As patients adapt to multifocal IOLs over a period of days to months, however, these symptoms typically become less bothersome and may disappear altogether.

Adaptation to multifocal IOLs is similar to adapting to the limitations of a monovision correction produced by monofocal IOLs or contact lenses, Dr. Holt says.

Examples of currently available multifocal IOLs include:

• AcrySof IQ ReSTOR (Alcon)
• ReZoom (Abbott Medical Optics)
• Tecnis Multifocal IOL (Abbott Medical Optics)

Phakic IOLs

Phakic IOLs are refractive intraocular lenses designed to be implanted without removal of the eye’s natural lens to correct large amounts of myopia.

Patients who opt for phakic IOLs typically are younger than age 45 and may not be good candidates for LASIK or other laser vision correction procedures.

Phakic IOLs can be implanted in front of the pupil (anterior chamber phakic IOLs) or behind it (posterior chamber phakic IOLs).

Anterior chamber phakic IOLs are attached to the front of the iris and are therefore somewhat visible. Posterior chamber phakic IOLs, on the other hand, are virtually invisible behind the pupil.

Desirable features of phakic IOLs include:

1. Because the natural lens is left intact, young patients retain their normal focusing ability and are not forced to wear reading glasses prematurely.
2. Phakic IOLs can be removed if cataract surgery becomes necessary later in the patient’s life.
3. In many cases, phakic IOLs can safely correct higher amounts of myopia than LASIK and other types of laser vision correction.

FDA-approved phakic IOLs include the Visian ICL, a posterior chamber phakic IOL manufactured by STAAR Surgical (Monrovia, Calif.) and the Verisyse Phakic IOL, an anterior chamber lens manufactured by Abbott Medical Optics (Santa Ana, Calif.).

Education and patient expectations are key

Dr. Holt advised his fellow eye doctors to appropriately screen and educate their patients about currently available premium IOLs.

A good understanding of the features, benefits and limitations of current IOL technology and having realistic post-operative expectations are key to patient satisfaction after surgery, he says.

SOURCE:  Understanding the latest IOL technology. Optometric Management. June 2009.