Modern cataract surgery is no longer simply extraction of an opaque crystalline lens and implantation of an IOL. With technological advances in devices and IOLs, the refractive aspect of cataract surgery has received more attention. We can achieve good refractive predictability with the use of biometry through interferometry and fourth-generation IOL power calculation formulas, and we can also correct preexisting or surgically induced astigmatism, but presbyopia continues to present challenges. Lens technologies have evolved; however, no IOL is capable of satisfying 100% of patients who wish to do without their glasses. Advances in IOLs and related technologies have contributed to the problem, because they have increased cataract patients' expectations and demands regarding refractive outcomes. We must be wise and use good sense to control the enthusiasm and manage the expectations of patients, thereby obtaining success with our procedures.
We have implanted both multifocal and accommodating IOL models in our practice, and our experience suggests that, with proper patient selection and education, these devices can satisfy the visual requirements of many presbyopic patients with cataract.
MULTIFOCAL IOLS
Currently, multifocal IOLs are the best way for most
patients to achieve spectacle independence. In the past 6
years we have implanted almost 6,000 multifocal IOLs.
In 2004, we began implanting a new generation of multifocal lenses, the AcrySof IQ Restor Aspheric +4.0 D (SA60D3; Alcon Laboratories, Inc., Fort Worth, Texas) and the ReZoom multifocal (Abbott Medical Optics Inc., Santa Ana, California). Despite great improvements in relation to the previous-generation Array (Abbott Medical Optics; no longer available), these multifocal IOLs were still associated with unwanted visual phenomena.
The Restor diffractive multifocal (SA60D3) offers near vision at approximately 20 to 30 cm and requires good lighting conditions for reading due to its 12 apodized diffractive rings. The ReZoom zonal refractive lens provided near vision at a more convenient distance of approximately 30 to 40 cm and intermediate vision better than that of the Restor. Still, in some patients near vision was not satisfactory, probably due to the lens' dependence on pupil size.
In order to satisfy patients, we began to mix and match these two lens designs. Patients achieved almost 100% independence from glasses.1
In 2006, the diffractive Tecnis Multifocal IOL (ZM900; Abbott Medical Optics) was introduced. Patient satisfaction was greater with this lens because it is pupil independent, allowing good distance (Figure 1) and near (Figure 2) vision. In our experience, visual results were even better when the target of final refraction was 0.50 D, thus improving intermediate vision (Figure 3). However, patients experienced more halos than with the Restor and ReZoom.
Even with this improvement, the number of multifocal IOL implants we performed did not increase due to limited indications. Patients with good quality of vision for distance (due to low amounts of higher-order aberrations) who submitted to presbyopia correction with clear lens exchange did not experience satisfactory results because their quality of vision was diminished and photic phenomena were introduced.
At that time, we began to study the effects of neural adaptation on visual results with multifocal IOLs, informing patients about the process of neural adaptation. We experienced a great decrease in the number of complaints regarding photic phenomena after 6 months of adaptation. For this reason, we believe one should never explant a multifocal before this adaptation period has been completed.
Only 6.9% and 11.5% of IOLs implanted in the United States and Europe, respectively, are multifocal (Market Scope data). In contrast, at our practice, 50% of patients receive a multifocal IOL implant.
We consider the Acrysof IQ Restor +3.0 D and the latest model of the Tecnis IOL with reduced chromatic aberration to be the newest generation of multifocal lenses. These IOLs provide much higher quality of vision than previous models. The Acrysof IQ ReStor +3.0 D provides near vision at a farther distance and generates less perception of halos because of its reduced number of apodized rings (nine rings, three less than the +4.0 D model).
FROM SUBJECTIVE TO OBJECTIVE CRITERIA
When we began implanting multifocal IOLs 6 years ago,
we noticed how important understanding the patient's
lifestyle was in choosing the best IOL. Although lifestyle is
still important, it is no longer fundamental in making the
choice. Today, a compulsive computer user, a tennis player
who plays at night, a professional driver, and even a pilot
can benefit from these lenses, which in the past we would
not have recommended for them.
Today our criteria are more objective and less subjective. Regarding subjective criteria, (1) the importance of spectacle independence to the patient should be determined, and (2) despite the reduction in photic phenomena with newer lenses, the possibility of these occurring should be explained to patients.
Objective exams that should be employed include aberrometry to measure quality of vision, especially in emmetropic patients and those undergoing clear lens exchange (Figure 4).
The ocular media should be transparent. The cornea cannot present opacities or irregularities, and any eye with vitreous opacity should be excluded. We must remember that such opacities, or even recent vitreous detachment, cause much greater visual disturbance in patients with multifocal lenses. In our experience with multifocal IOLs, we have performed approximately 35 posterior vitrectomies due to vitreous opacity, and in 100% of cases the patients' complaints decreased.
The health of the tear film should be evaluated exhaustively because 50% of postoperative complaints in patients with multifocal lenses are related to lacrimal conditions.
Macular function is another important objective test. Visual acuity of 20/20 on the Snellen chart or 20/20 as measured by potential acuity meter may not be sufficient to guarantee the satisfaction of patients with multifocal lenses. A macular visual field exam should be performed, and a threshold of less than 28 dB at any macular point should indicate a negative recommendation for the procedure.
It is important to remember that light energy is divided between or among the foci in multifocal lenses, and for this reason we do not recommend them for any patient with alteration in macular function. I do not recommend them for patients with only one eye.
Astigmatism correction is also mandatory. Multifocal lenses do not achieve good results in patients with this form of ametropia. When limbal relaxing incisions (LRIs) are recommended, peripheral pachymetry should be performed. LRIs will not achieve their objective unless they reach 90% of corneal thickness.
PREVIOUS REFRACTIVE SURGERY
Patients who have previously undergone refractive surgery
can experience good visual results with multifocal
IOLs, but there are special considerations. Patients with
previous radial keratotomy (RK) and those who have
undergone LASIK should be considered separately.
We have done a retrospective analysis of 42 eyes (22 patients) with previous RK for myopia who underwent phacoemulsification with implantation of a multifocal IOL (Tecnis ZM900 or AcrySof Restor). The average preoperative spherical equivalent (SE) was 0.40 ±1.75; average preoperative preoperative distance UCVA was 0.54 ±0.37; and average preoperative distance BCVA was 0.17 ±0.22. Postoperatively, SE was -0.53 ±0.99 (P<.001), average distance UCVA was 0.30 ±0.26 (P<.001), average distance BCVA was 0.07 ±0.09 (P<.001). A secondary procedure was performed in eight eyes (20%). At the last follow-up, all eyes achieved near UCVA of J1. These data show that multifocal IOLs can improve distance and near vision, reducing dependence on glasses with reasonable results, even in eyes with previous refractive surgery.
Post-RK patients with unstable corneas due to open incisions should be avoided because final emmetropia will not be achieved. When we consider a recommendation for multifocal lenses in these patients, a drop of fluorescein is placed on the cornea, and the four quadrants of the sclera are depressed. If the incisions open and show color, they have not healed, and the cornea is unstable. These patients rarely complain of photic phenomena because they have already adapted to the glare and halos that occur due to corneal flattening and scarring.
In post-LASIK patients, the thickness of the cornea should be determined because they have a greater chance of needing enhancement for correction of residual ametropia after the implantation of multifocal IOLs.
ACCOMMODATING IOLS
We consider accommodating IOLs to be monofocal
lenses. The mechanism of action of these lenses is unclear.
We do not know whether intermediate and near vision are
provided by lens mobility or by artificial aberration generated
by possible lens tilt.
The great advantage of these IOLs is that the patient will never complain of photic phenomena such as halos and glare. Patients with clinical conditions that preclude implantation of multifocal IOLs can benefit from accommodating lenses. It is imperative that patients should be informed that they may not have the same efficacy for near vision as patients with multifocal lenses.
In our experience, most patients are able to achieve J3 near vision and generally need glasses for reading, with no accompanying glare or photic phenomena. Accommodating IOLs offer excellent vision in the long and intermediate ranges. Our experience with the Crystalens (Bausch + Lomb, Rochester, New York) is shown in Figures 5 through 7.
We recommend accommodating lenses for the following indications: patients who do not mind needing glasses for reading at times; patients who expect the best quality visual acuity for distance; patients with reduced macular function (macular visual field); young diabetic patients with no maculopathy; patients with drusen or the beginning of any other retinopathy; patients with floaters; patients with one eye; and patients with corneal opacity.
CONCLUSION
When presbyopia-correcting IOLs are properly recommended,
patients' expectations are consistent with their
visual results, the doctor-patient relationship is preserved,
and surgery is perceived as the state of art.
We must know our patients well and be aware of their needs and requirements. We can thus meet our responsibilities, and patient can achieve his level of expectation.
Leonardo Akaishi, MD, is Director of the
Hospital Oftalmológico de Brasília, Brazil. He
states that is a panelist and member of the scientific
advisory board for Abbott Medical Optics
Inc., Alcon Laboratories, Inc., and Vistatek. He
may be reached at tel: +55 61 34 42 40 00; e-mail: leonardoakaishi@
uol.com.br.
Newton Andrade Jr, MD, a participant in the cataract fellowship
program of the Hospital Oftalmológico de Brasília,
Brazil. He states that he has no financial interest in the products
or companies mentioned. He may be reached at tel: +55
61 8609 2020; e-mail: Newton.jr@globo.com. Marcio Nutels, MD, is a participant in the cataract fellowship
program of the Hospital Oftalmológico de Brasília,
Brazil. He states that he has no financial interest in the products
or companies mentioned. He may be reached at tel: +55
61 9199 1122; e-mail: munutels@hotmail.com
