High expectations in pseudophakia fuel hyperrefraction

February 1, 2008

Recipients of a premium IOL have high expectations for excellent uncorrected distance visual acuity. The availability of these implants has created a new patient base for laser vision correction. Considerations for performing laser enhancement are discussed.

Key Points

Patients with a multifocal IOL implanted are exquisitely sensitive to ametropia-related image degradation, he observed. Although several options are available for correcting residual refractive errors in sphere, cylinder, or both, laser vision correction is the most accurate.

Before pursuing laser enhancement, it is important to be certain that the patient's dissatisfaction is due to ametropia, he said. Some potential causes of vision complaints include capsular opacity, dysphotopsia from a multifocal IOL, or dry eye. Multiple factors may exist simultaneously in the same patient.

"A contact lens trial may also be useful to simulate the benefit of an enhancement procedure, and existing dry eye should be addressed in any patient when laser enhancement will be performed," noted Dr. Dell.

Timing is everything

Because these patients may be particularly anxious for better vision, it also is important that they understand that the timing of an intervention must be determined by medical prudence rather than by their desire to see well immediately. Although a flap may be cut prior to the IOL surgery if it is anticipated that enhancement will be necessary, such as in a patient with high astigmatism, a postoperative waiting period of 3 months is recommended when cutting a flap with a mechanical microkeratome.

"If a femtosecond laser is used for flap creation in an eye that has undergone small-incision lens removal with IOL implantation, it is probably safe to proceed with the enhancement 45 to 60 days postop," said Dr. Dell.

When a decision is made to proceed with a laser vision enhancement, surgeons need to consider whether to perform a customized ablation or a conventional procedure. Results of various studies across multiple platforms demonstrate that a custom wavefront-guided procedure consistently provides superior results when compared with a conventional ablation, Dr. Dell said. In addition, for one platform (VISX CustomVue, Advanced Medical Optics [AMO]), three separate studies that compared customized treatment performed with iris registration versus without iris registration showed that in the challenging-to-treat group of patients with high astigmatism, rates of 20/20 or better UCVA were significantly higher in the iris registration group, he said.

Dr. Dell suggested performing a wavefront-guided procedure in patients with a monofocal IOL, an accommodating IOL (crystalens, eyeonics), or with either of the diffractive multifocal IOLs (AcrySof ReSTOR, Alcon Laboratories; Tecnis, AMO) implanted, assuming the wavefront is capturable and the data make sense. He cautioned, however, against a custom wavefront-guided enhancement in patients with the zonal refractive multifocal IOL (ReZoom, AMO) implanted because those eyes may not be reliably imaged with available wavefront analyzers and, therefore, might be at risk for an unpredictable result.

"The opportunity to perform a wavefront-guided enhancement after IOL implantation may also be limited in older patients, because smaller pupil sizes can also cause difficulty with wavefront imaging. However, the amount of correction needed for these enhancements is generally small, and even if customized treatment is not possible, excellent results can also be achieved using a conventional ablation profile," Dr. Dell said.

In patients with extremely high ametropia postop, IOL exchange may be a better option than enhancement, he said.

"If exchange is being considered, early intervention will be technically easier than a delayed procedure. However, late exchanges can be undertaken safely with careful technique and judicious use of viscodissection of the capsular leaves. If the patient has developed posterior capsule opacification, Nd:YAG laser capsulotomy should be deferred if IOL exchange is being considered, since an open posterior capsule will complicate the surgery," Dr. Dell said.