Laser enhancement important adjunct to multifocal IOL

September 15, 2007

The bar for refractive and vision outcomes has been raised in patients in whom multifocal IOLs have been implanted. Laser vision correction, therefore, has become an important enhancement tool. Multifocal IOL patients should be managed the same as laser vision refractive surgery patients, but additional issues should be considered.

Key Points

Baltimore-Laser vision correction can be a valuable tool for optimizing refractive outcomes after multifocal IOL implantation, said Alisa Kim, MD, at the Current Concepts in Ophthalmology meeting.

"With the introduction of new multifocal IOL platforms, we have seen a paradigm shift such that the postoperative goal has moved beyond achieving restoration of best spectacle-corrected visual acuity (BSCVA) into the realm of restoring the best uncorrected visual acuity (UCVA) to afford spectacle independence," said Dr. Kim, cornea division, Wilmer Eye Institute, School of Medicine, Johns Hopkins University (JHU), Baltimore.

"With outcomes expectations raised, cataract surgery has become a part of a broader refractive package that includes multifocal IOL implantation combined with laser vision correction to fine-tune the refractive result."

"Cataract surgeons implanting these multifocal IOLs who are not now performing laser vision correction should consider adding it to their practice or teaming up with a colleague who does," Dr. Kim continued. "Multifocal IOL patients need to be managed in the same way as elective laser vision correction patients, taking added precaution [because] laser vision correction after IOL implantation is an off-label procedure and requires special considerations."

The idea of "bioptics," the planned combination of phakic or pseudophakic IOL surgery with corneal surgery to correct large refractive errors, was popularized by Roberto Zaldivar, MD, in the late 1990s. In various studies, the use of laser vision correction to optimize refractive outcomes has been shown to be useful in eyes with phakic, monofocal pseudophakic, and-increasingly now-multifocal pseudophakic IOLs. Bioptics may be planned as a procedure to correct astigmatism, or it may become indicated as an unplanned procedure to treat postoperative refractive surprises.

Addressing astigmatism

"Achieving excellent vision quality with a multifocal IOL depends on minimal residual astigmatism. Some astigmatism may be addressed by strategic positioning of the cataract incision. However, because the currently available multifocal IOLs do not correct for astigmatism, planned corneal refractive surgery may be necessary in a patient with pre-existing high astigmatism," Dr. Kim said.

"Therefore, all patients should be considered potential candidates for laser vision correction beginning at the time of the preoperative evaluation. In addition, there is always a potential for sphere or cylinder surprises," she added.

The surgical options for correcting residual sphere include laser surgery, IOL exchange, or placement of a "piggyback" IOL.

"The surgeon should carefully weigh the cost:benefit ratio of each of these options, recognizing that piggybacking or exchanging an IOL is intraocular surgery that is accompanied by risks, such as corneal edema, endothelial cell loss, cystoid macular edema, capsular compromise, and retinal detachment," Dr. Kim said.

In eyes with residual astigmatism exceeding 1 D, an incisional technique or laser vision correction can be considered.

When performing a laser vision correction procedure, it is necessary to wait until there is stability of refraction, the cataract wound, and any incisions made to correct astigmatism. Then a decision needs to be made whether to perform LASIK or a surface ablation procedure, and next whether to use a conventional or custom ablation treatment.

Because of the increased IOP associated with the flap creation, LASIK may present possible issues in eyes with prior limbal-relaxing incisions and usually requires a longer waiting period after the IOL surgery when compared with PRK. LASIK, however, has the advantage of resulting in more rapid vision recovery after the surgery.

A customized procedure performed with iris registration to compensate for cyclotorsional rotation of the eye and pupil centroid shift has the potential to result in more precise treatment of astigmatism compared with a conventional procedure. It may not be possible to capture an optimal wavefront analysis in all patients, however. For example, using one system (WaveScan WaveFront, VISX/Advanced Medical Optics), patients need to have a pupil diameter of at least 5 mm. It is also important to recognize that posterior capsule opacification (PCO) can compromise the quality and accuracy of the analysis.

"If a custom procedure is being considered, it is critical that there is agreement between the manifest and wavefront refractions," Dr. Kim said.

Pupil and capsule issues also may affect performance of the iris registration. A conventional procedure, therefore, may be a better option than a customized ablation for certain patients. It is still important to be certain that the patient's UCVA is consistent with the manifest refraction and that the manifest refraction correlates with the topography and keratometry measurements, however.

In addition, when planning laser vision correction, surgeons should take into account that PCO-related symptoms will develop sooner and be more problematic for patients with multifocal IOLs relative to persons with monofocal IOLs. If treatment for PCO is indicated, it should be performed prior to laser vision correction, because the capsulotomy may cause a shift in lens position and refraction, Dr. Kim said.