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Pseudoaccommodative and aspheric lenses creating ‘new standards’ in IOL technology
As cataract surgery increasingly becomes a refractive procedure, surgeons and industry update solutions.
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FLORENCE - Current approaches to cataract surgery aim at two principal goals. The first is to provide patients with good quality of vision, which means improved contrast sensitivity in all light conditions and a decreased chance of unwanted visual disturbances. The second is to reduce postoperative spectacle dependence by achieving good uncorrected distance, intermediate and near vision. Speakers at the Florence Symposium, the Joint Meeting of Ocular Surgery News, the Italian Association of Cataract and Refractive Surgery and the Italian Society of Ophthalmology, largely focused on these issues and on the IOL technology that is translating these goals into realistic options for patients and surgeons.
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As cataract surgery increasingly becomes a refractive procedure, the newest generation of pseudoaccommodative IOLs is likely to become the “new standard,” according to a number of surgeons.
Many speakers said that new pseudoaccommodative IOLs — lenses that provide the patient with more than one point of focus without movement in the eye — have compared favorably with other options for correction of presbyopia, such as modified monovision and accommodative IOLs.Among the newer IOL technologies, diffractive technologies are favored by some cataract surgeons. The apodized diffractive design of Alcon’s AcrySof ReStor lens improves visual quality and diminishes the chance of unwanted visual disturbances, such as glare and halos, Stephen F. Brint, MD, told attendees.
“The lens offers excellent distance and near vision, and although intermediate vision requires some adaptation, 80% of patients are entirely spectacle-free,” Dr. Brint said.
The aspheric profile of Advanced Medical Optics’ multifocal Tecnis lens “compensates for spherical aberration and therefore provides even better contrast sensitivity and improved night driving capability,” according to Michael C. Knorz, MD.
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Refractive multifocal implants, such as AMO’s recently approved ReZoom, have improved their performance by combining new materials and optic designs that minimize the well-known problems of glare and halos produced by previous models, speakers said.
Careful patient selection and lens choice remain crucial issues with pseudoaccommodative implants, the group agreed.
Although these lenses “are becoming an increasingly important tool in the armamentarium of cataract surgery, they are not suitable for all our patients,” said Johann Kruger, FCS (SA)Oph, FRCSEdin(Oph). “Patients with unrealistic expectations are better avoided.”
Simultaneous bilateral surgery
Both Dr. Kruger and Richard Packard, FRCS, FRCO, recommended simultaneous bilateral implantation of pseudoaccomodative lenses.
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“Although there have been considerable advances in pseudoaccommodative lens technology, multifocality always requires some brain adaptation, which is made easier and faster if the task is addressed by the two eyes simultaneously,” Dr. Packard said.
Although simultaneous surgery raises some controversy among surgeons, he believes it is a safe procedure that saves time and money for patient and surgeon.
Of 90 patients who underwent bilateral simultaneous surgery with implantation of the ReStor lens, none reported that they would have preferred to have their surgery done in two sessions, Dr. Packard said. Visual acuity results were good, and no intraoperative or postoperative complications were related to consecutive surgery.
If some degree of ametropia remains after the implantation of a multifocal lens, LASIK or piggybacking can be effective solutions, he said.
“Now that problems with intralenticular membranes have been solved by placing one lens in the sulcus and one in the capsular bag, piggybacking can be reintroduced for several refractive enhancement procedures,” Dr. Packard said.
Novel uses of piggybacking include the addition of a multifocal lens for a pseudophakic patient, he said.
Aspheric IOLs
Patient quality of vision can be enhanced by the use of aspheric IOLs, according to two speakers here. Aspheric IOLs may have a negative spherical aberration to neutralize the positive spherical aberration of the normal cornea or may be spherical aberration-free. Each design has inherent benefits for the patient.
Functional vision and the ability to see at low levels of contrast decline with age because the crystalline lens is no longer capable of compensating the positive spherical aberration of the cornea.
The AMO Tecnis lens was designed specifically to address this issue, according to Kenneth J. Rosenthal, MD. As in a young, healthy crystalline lens, the modified prolate anterior surface of this IOL compensates for the positive spherical aberration of the cornea by using negative asphericity.
The benefits of this new design are particularly evident in mesopic conditions, Dr. Rosenthal said.
“At twilight, or with rain, snow and fog, older drivers have a great deal of difficulty with contrast sensitivity and have a higher chance of being involved in road accidents. This is a very serious problem that cataract surgery with conventional IOL implantation does not address, as it restores the vision to a level that is equivalent to that of older people,” he pointed out.
The Tecnis lens restores vision similar to that of younger, healthy eyes and increases the ability of older eyes to detect obstacles while driving. Consequently, it is likely to have a considerable impact on the improvement of driving in that segment of the population, he said.
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However, a lens that induces no spherical aberration might be a “more reasonable choice” in the average clinical setting, according to Richard L. Lindstrom, MD.
“Ideally, an aspheric IOL with negative spherical aberrations, such as the Advanced Medical Optics Tecnis, can give the best results in terms of quality of vision, because it neutralizes the positive spherical aberrations of the cornea,” he said at the meeting.
“However, the smallest decentration or tilting of the lens will induce coma, which degrades the image. For these lenses, you need a perfect surgery,” he added.
An aspheric lens that may be “more forgiving” of decentration or tilt, such as the Bausch & Lomb SofPort Advanced Optics IOL, is probably the best compromise, Dr. Lindstrom suggested. The B&L lens is designed to be aberration-free once implanted, he said.
AquaLase for younger patients
AquaLase could become the procedure of choice for the growing number of patients undergoing lens surgery at a younger age, according to Dr. Brint.
“Nowadays cataract surgery is diagnosed and treated earlier than it used to be,” he said. “In addition, the new accommodative and pseudoaccommodative IOL options are encouraging an increasing number of patients to chose clear lens exchange as a refractive procedure.”
This group of patients is likely to have less dense nuclei, ranging from trace cataract to a low 3+ density, Dr. Brint said. For these younger patients, safety is a vital issue, he added.
“The AquaLase allows for a safer procedure, with no tunnel burning, reduced risk of capsule rupture and a more accurate cleaning of the posterior capsule,” he said.
Phakic IOLs, lens exchange
Several discussions during the meeting concluded that clear lens exchange is still a controversial topic. Clear lens exchange is not a widely accepted procedure for those of pre-presbyopic age, and for patients less than 40 years old, laser refractive surgery or phakic IOLs are still more popular options.
The reliability and efficacy of the many phakic IOLs available on the market was demonstrated by long-term follow-up studies presented by a variety of speakers, and ultrasound biomicroscopy studies also showed positive long-term results. Sizing, however, remains a crucial issue with both posterior and anterior chamber implants.
Matteo Piovella, MD, also emphasized the importance of regular visits at 6-month intervals after phakic IOL implantation.
“Patients should be clearly instructed that they should not miss their postoperative appointments and should be informed of the potential consequences of a careless attitude,” he said.
A new way of implanting the Ophtec Artisan lens in some patients was suggested by Cesare Forlini, MD. The lens, he said, can be fixated on the posterior surface of the iris, offering the surgeon several advantages over other fixation points.
“The natural pressure of the aqueous from the inside of the eye squeezes the IOL against the posterior surface of the iris, enhancing stability, preventing tilting of the lens and glare phenomena,” he pointed out.
Hidden behind the iris, the lens also offers a better cosmetic appearance for the patient, reducing the characteristic reflex of the lens optic that is visible at short distances.
Enclavation behind the iris is “fairly easy,” Dr. Forlini said. The lens is introduced through a 4.5-mm incision, guided to the correct position with a Barraquer spatula and enclavated with forceps.
“You can feel the holes in the haptics through the iris,” he said.
Gentle approach to presbyopia
Alternative, less invasive methods of correcting presbyopia were suggested by some surgeons. Dr. Lindstrom said he is seeing good results from intracorneal lenses, which have the advantage of an easy, safe and reversible procedure. He noted that three companies are currently working on these implants.
“Patients have to sacrifice about 1 D of distance vision, but gain in near and intermediate vision,” he said. Intracorneal lenses are used to obtain modified monovision and are implanted in one eye only.
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José L. Güell, MD, presented his preliminary results with a new presbyopic profile for the Carl Zeiss Meditec MEL80 excimer laser, which is based on the Zernike 4.0 aberrometric treatment to induce positive spherical aberration. The aim of the treatment is to reshape the presbyopic eye to make it similar to a moderately hyperopic young eye.
This treatment algorithm, developed by Franco Bartoli, MD, in collaboration with Carl Zeiss Meditec, is based on the assumption that the young, moderately hyperopic eye focuses at far and at near by increasing the curvature of the lens. It is in a permanent state of accommodation and therefore of positive spherical aberration.
“In spite of this induced aberration, visual quality is good, and there is no need for spectacle correction. We want to recreate these conditions by inducing a certain quantity of spherical aberration on the cornea,” Dr. Güell said.
Beside the improvement in near vision, he pointed out, the main advantage of this approach has been the absence of negative side effects.
Dr. Bartoli said during the symposium that he has been treating contact lenses with the same procedure and has tried it on a number of presbyopic friends.
Endophthalmitis rise
The clear corneal incision, a staple of cataract surgery technique since the 1990s, may be responsible for a dramatic increase in the incidence of endophthalmitis over the past decade, several speakers said.
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The transient IOP drop that follows phacoemulsification might cause the unsutured wound to open and allow fluid to carry bacteria into the eye, suggested Terrence P. O’Brien, MD.
Samuel Masket, MD, suggested that the IntraLase FS femtosecond laser may allow surgeons to create a better self-sealing incision.
“The laser beam produces the corneal tunnel from the inside to the surface, and all you need is to deepen it slightly with a blade until you reach the anterior chamber” he said. “In this way, incisions don’t leak.”
Alternatively, Terry Kim, MD, suggested using a self-sealing glue to seal the incision. He said the adhesive does not dissolve in the watery corneal environment and will form a stable protective barrier over the wound.
Dr. O’Brien said an easier solution may be the use of a Vicryl suture in selected cases.
“It’s a very cost-effective investment when you suspect the incision might be leaking,” he noted.
For Your Information:
- Michela Cimberle is an OSN Correspondent based in Treviso, Italy.