Multifocal intraocular lens offers duality in treating phakic and pseudophakic patients

April 15, 2008

An anterior chamber diffractive multifocal IOL (Vision Membrane, Vision Membrane Technologies) designed as a phakic implant has been used successfully to treat ametropia and presbyopia in pseudophakic eyes. The technology, its benefits, and the outcomes achieved are described in this article.

Key Points

New Orleans-A novel anterior chamber diffractive multifocal IOL (Vision Membrane, Vision Membrane Technologies) shows promise as an option for simultaneous correction of distance and near vision in both phakic and pseudophakic patients, said Lee T. Nordan, MD.

Speaking at the refractive surgery subspecialty day preceding the American Academy of Ophthalmology annual meeting, Dr. Nordan reported that the multifocal lens has been used successfully as a phakic implant to correct myopia in about 50 eyes. He discussed the first experience implanting it to correct pseudophakic ametropia and presbyopia. In both situations, the IOL has been associated with good refractive and vision outcomes and provides excellent image quality without significant haloes or glare, regardless of pupil size.

"A major challenge facing researchers working to develop methods for treating presbyopia is to ensure the modality provides high-quality vision across the distance spectrum from near to far," said Dr. Nordan, a former assistant clinical professor, Jules Stein Eye Institute, University of California, Los Angeles, and recently retired. "With its outstanding optics, I believe the . . . multifocal technology [in this lens] represents improved optics and is a major advance in our ability to provide functional distance and near vision to virtually all patients with refractive error."

The implant has a silicone optic that measures 6 mm in diameter and 600 µm thick, regardless of power. It is foldable and implanted through a sub-3.0-mm incision using an injector, and it fits well into the angle of the anterior chamber, where its unique haptics exert just enough force against the trabecular meshwork to maintain IOL position, he said.

Most of the vault of the implant is derived from the vertically curved haptics rather than from compression of the haptics. The predictable vaulting and thinness of the optic ensures that adequate clearance from the corneal endothelium exists and allows patients to obtain the benefits of a full 6-mm optic with good safety and without the need for a peripheral iridectomy, Dr. Nordan said.

The anterior chamber multifocal IOL was designed as a phakic implant, but because the anterior chamber of the eye is not involved by posterior chamber (PC) IOL surgery, it was reasoned that the lens also might be used in eyes with a single-vision PC-IOL, to treat residual ametropia and presbyopia.

The first case of implantation in a pseudophakic patient that Dr. Nordan described involved a woman, aged 82 years, who underwent monocular implantation of the diffractive multifocal IOL in an eye 9 months after cataract surgery. The patient's vision was plano in her right eye, with best-corrected visual acuity of 20/25 and only mild nuclear sclerosis.

After implantation of a monofocal PC-IOL in her left eye, she had a –7.00-D spherical error (SE) and complained of anisometropia. With spectacle correction, she achieved 20/25 visual acuity in the left eye for distance and 20/25 at near (35 cm) using a +3.00-D add.

David Castillejos, MD, implanted a –7.00 D/+2.00 D add version of the multifocal IOL in the patient's pseudophakic eye. On the first day after surgery, SE in the left eye was –0.25 D and the patient's uncorrected visual acuity was 20/25 at distance and 20/25 as well over an extended reading range of 14 to 20 inches.

"The most remarkable finding in this patient was her depth of field, which is equivalent to spectacles with an add of +2.00 to +3.00 D. To maintain the same excellent visual function over that near to intermediate distance range is an astounding and important clinical result," Dr. Nordan said.

Distance and near visual acuity were unchanged after pupil dilation, and the patient's vision and refractive outcomes have remained stable during follow-up that now extends for 4 months. Similar results have been achieved in a second pseudophakic patient with a PC-IOL who was nearly emmetropic but reading 20/80 uncorrected at near. Both patients are very satisfied with their outcomes.

"The fact that the visual acuity is the same with a physiologic and dilated pupil indicates that the effective add power is related to the optic design rather than a consequence of some pseudo-accommodative phenomenon such as pupillary diameter," Dr. Nordan said.

To demonstrate further the superb quality of vision provided by the multifocal IOL, Dr. Nordan presented images obtained by means of wavefront analysis (OPD-Scan, Nidek) from a phakic patient's eye in which the lens had been implanted and compared these images with those of both eyes of a patient in whom apodized diffractive IOLs (AcrySof ReSTOR, Alcon Laboratories) had been implanted. After room illumination was adjusted to cause a mild increase in pupil size, significant image degradation clearly was visible in the eyes with the apodized diffractive lenses implanted, whereas the quality of the image was minimally affected for the eye with the novel anterior chamber diffractive multifocal IOL.