Multifocal Implants

Chapter 16

Farrell (Toby) Tyson, MD, FACS


When getting started with multifocal intraocular lenses (IOL), it is just as important to choose the right patient as it is which type of multifocal. Many surgeons start out their multifocal careers in disappointment by choosing a medical outlier for their first patient. Your multifocal patients should be some of your happiest patients, because you are “cherry picking” them from the start.

Initial evaluation should start with your basic biometry before you enter the examination room. This helps you lead the discussion with patients in an efficient manner. First, evaluate the amount of astigmatism. The keratometric astigmatism magnitude should be under 1 diopter (D) to start with. This low level of astigmatism is generally well tolerated by patients with multifocals and may not require enhancements. Next, evaluate the type of astigmatism. If the astigmatism is asymmetric, then exclude this patient, as even future enhancements will be difficult. Small amounts of symmetric astigmatism can easily be dealt with by wound placement, small limbal relaxing incisions (LRI), or femtosecond laser astigmatic incisions.

Multifocal IOLs do well in a large range of axial lengths. When starting out, I would recommend staying in the more normal ranges. This is due to the inherent loss of IOL power accuracy at the extremes, which leads to a higher likelihood of IOL surprise, which is poorly tolerated in multifocal IOLs. Low hyperopes are some of the best initial patients for multifocals, because you are taking a patient with poor uncorrected distance and near vision and giving them both. The bar is low with these patients. High hyperopes would seem like equally easy patients to satisfy, but effective lens position is harder to predict in these smaller eyes, which can lead to a refractive surprise. This can be equally true of high myopes. Caution must be used in selecting low myopes for multifocals. Their uncorrected preoperative near vision is usually pretty good and at a set focal length. Operating on a low myope may give him or her the best of both worlds but may also change his or her near working distance and magnification. Careful preoperative counseling is necessary for success.

Basic eye pathology needs to be assessed next. The majority of your multifocal patients are going to be in your cataract age group. This same group of patients usually has some dry eye issues. The extent of their dry eyes needs to be evaluated and treated first, before multifocal implantation. Most patients’ conditions are easily controlled with artificial tears, gel, or punctual plugs. If further treatment is necessary, cyclosporine ophthalmic drops can be very beneficial. If the dry eye symptomatology does not abate with treatment, then monofocal implantation should be considered. Ocular surface disease causes a loss of contrast and an increase in glare, which is incompatible with multifocal IOLs.

Endothelial health should be evaluated. Moderate to severe guttata should be avoided, as it leads to loss of contrast sensitivity. The presence of pseudoexfoliation or zonular instability should be ascertained. In early cases, these patients should be excluded, but with greater experience they may be successfully treated with the use of 3-piece multifocals and/or capsular tension rings. The concern being short- and long-term lens stability and centration.

Posterior pole evaluation should be relatively benign. Make sure to look for small epiretinal membranes. They have a tendency to cause trouble in your multifocal patients. A preoperative macular optical coherence tomography evaluation may save you hours of headaches by evaluating retinal structure. In addition, a flicker pattern electroretinogram can elucidate potential problems by evaluating retinal function. Active diabetic retinopathy or macular drusen/degeneration are additional red flags. To achieve initial success with multifocal IOLs, one needs to limit the number of possible complications.


Setting the expectations for patients may be the most difficult part of multifocal IOL implantation for the beginning surgeon. This is because most surgeons have not been trained to interact personally with patients or in the past have deferred this task to surgery counselors or technicians. Multifocal patients have high demands from the beginning. They expect more because they are paying more. These expectations include the fact that they want real interaction with their surgeon. This is your chance to set the stage and manage expectations. If you don’t, the patient is always going to be disappointed, because they walk in expecting perfect vision at all distances.

We have all heard the phrase, “under promise and over deliver.” That is easier said than done. I like to start by letting the patient know that there is nothing perfect in life, especially cataract surgery, but the technology has come a long way and we can now help provide a fuller range of vision. I let them know not to expect 18-year-old eyes. On the other hand, I like to have them hold a reading card at the appropriate working distance and show them what they can reasonably expect of their postoperative near vision and where.

Different multifocals perform differently at different near focal lengths and under different conditions. This allows you to tailor the lens to the patient’s lifestyle. A good general opening question is “What do you like to do?” This helps you realize whether the individual is detail-oriented, a reader, or a more intermediate-task individual. One of the more defining traits is computer use. This task can steer your choice considerably. The ReSTOR (Alcon) aspheric 4.0 lens has a near focal length of 33 cm, the Tecnis ZMAOO and ZMBOO (Abbott Medical Optics) multifocal lenses have a near focal length of 37 cm, and the ReSTOR aspheric 3.0 lens has a focal length of 44 cm. The newer ReSTOR aspheric 2.5 lens has focal length of 50 cm. The low add Tecnis multifocals ZKBOO (2.75) and ZLBOO (3.25) have respective focal lengths of 50 cm and 44 cm. All of these aspheric multifocals provide excellent distance vision.

Dysphotopsias are probably the most important part of the preoperative discussion. If they aren’t addressed before the surgery, they will surely be after the surgery. Luckily, this current generation of multifocals has made great strides in reducing the perceived glare and halos at night by reducing the spherical aberrations in the ocular system. In addition, the migration toward lower add powers that require fewer rings has further reduced the perceived glare and halos of this category of IOLs. Many patients are now aware of premium lenses from their friends, with varying degrees of success and failure. It is appropriate to address the fact that older style multifocals did have significant glare issues.

Cerebral adaptation is difficult to convey to patients in scientific terms. I find it best to explain it to them through analogy. I tell them cataract surgery is like getting a new ring. “At first, you know it is there, and you look at it and play with it. Over time, though, you almost forget it is on, but if you look for it you can still see it. The same is true with your vision. Immediately after cataract surgery, everything is going to be brighter and more vibrant. At night, you might notice some rings and halos around lights. Over the next 3 months, that usually diminishes and goes away, but if you look for them, you can still find them.”

Cerebral summation has been shown to improve both distance and near vision by at least 1.5 lines of acuity. Therefore, I inform my patients not to expect much of their vision after the first eye, that it takes both eyes for the brain to truly utilize multifocal IOLs. This statement lowers their expectations between surgeries and allows for the second surgery to be performed in hesitant patients. Cerebral summation is very effective in masking the deficiencies of a single eye.


Multifocal IOL implantation requires not only accurate preoperative measurements but reproducible ones. Good outcomes are achieved when variability is minimized, and this can be done through optimization of your IOL power calculation formulas. Corneal topography should be performed on all multifocal candidates to rule out asymmetric astigmatism that could be masked on a manual or an optical biometry A-scan keratometer.

Axial length measurements are critical to success. This measurement should be obtained with either an immersion ultrasound unit, IOLMaster (Carl Zeiss Meditec), Lenstar (Haag-Streit), or other optical biometer. These methods are noncontact, accurate, and reproducible. Contact ultrasonography should not be used, as it allows for too much variability in axial length measurements.

Keratometry can come from a manual keratometer, corneal topographer, IOLMaster, Lenstar, or other method. One method should be chosen in a practice to maintain consistency so that IOL power calculation optimization can be performed accurately. Most practices have chosen to use an automated method to reduce the variability between different technicians.

Pupil size should be measured in both light and dark conditions. In the past, small pupils would rule out the use of ReZoom (Abbott Medical Optics) IOLs, as the reading benefit was lost. Now, patients with large photopic pupils may benefit from the Tecnis multifocal’s full diffractive optic in providing reading vision at large pupil sizes. The ReSTOR aspheric 4.0/3.0/2.5 become distance dominant at larger pupil sizes. Some patients present with very small and poorly dilating pupils. These patients lose the aspheric correction of the current multifocals due to the small pupil size and may have limited multifocality. These individuals would do better with a monofocal and probably will still have good depth of field due to the pinhole effect.

Corneal aberrometry can be obtained with some of the newer diagnostic equipment, such as the OPD III (Nidek), iTrace (Tracey), and Galilei (Ziemer). By obtaining the corneal spherical aberration, one can better match the appropriate multifocal IOL to minimize the total postoperative spherical aberration. Studies have shown that contrast sensitivity increases and glare decreases as spherical aberration is minimized. The average corneal spherical aberration in the cataract patient population is +0.27 microns.1,2 This can vary significantly from patient to patient and eye to eye, especially if refractive surgery has been previously been performed. The ReSTOR aspheric 4.0/3.0 lenses correct for 0.1 microns of spherical aberration, whereas the ReSTOR 2.5 lens corrects for 0.2 microns of spherical aberration. The Tecnis multifocal family corrects for 0.27 microns of spherical aberration. This difference in value allows the surgeon to custom match the IOL to the patient’s cornea for reduced glare and halos and better contrast sensitivity.

Angle kappa, the measurement between the pupillary center and the optical axis, has become more important in the assessment of potential multifocal IOL patients. As angle kappa increases, there has been a correlation with unhappy multifocal patients.3 Patients with large angle kappas, greater than 0.4 mm or 2.8 degrees when using a penlight,4 should avoid multifocal implantation.


Multifocal IOLs place a greater demand on the optical system of the eye. Therefore, there are some pathologies that are incompatible with the current multifocal IOLs. Most surgeons will not implant multifocal IOLs when any maculopathies are present. While early macular degeneration may show good postoperative visual potential, the disease course is known to be progressive. This contrast-reducing disease combined with a contrast-reducing lens platform is not the best combination. An aspheric monofocal IOL would be a better choice.

Diabetes, if well controlled without retinopathy, would not be a contraindication. If retinopathy is present and control is questionable, then multifocals should be avoided. Once again, we have to be considering how the retina is going to be not just 1 month postoperatively but 10 years postoperatively.

Glaucoma is another relative contraindication. If the patient has significant glaucomatous damage, then the macula has already lost some of it contrast sensitivity. In these glaucoma patients, a multifocal IOL would be contraindicated. Since the advent of better screening and treatment of glaucoma, many patients present with well-controlled intraocular pressures and no glaucomatous damage. These well-controlled glaucoma patients, with appropriate counseling, should have the option of multifocal IOLs.

Any corneal pathology that might reduce contrast sensitivity or induce glare should be avoided. Corneal scarring and gross dystrophies are relatively easy to diagnose. It is the more subtle changes that can be a problem postoperatively if left undiagnosed. Careful attention should be made for anterior basement membrane disease and mild corneal guttata; both can worsen postoperatively and severely degrade the performance of multifocal IOLs. Any evidence of keratoconus or pellucid marginal degeneration on corneal topography is a contraindication for multifocal IOLs.

When first starting with multifocal IOLs, all previous corneal refractive surgery patients should not be implanted with multifocal IOLs. Over time and experience, certain patients may benefit from multifocal IOLs only after thorough counseling. All radial keratometry patients are contraindicated from multifocal IOLs due to their refractive instability. Prior hyperopic LASIK or photorefractive keratectomy (PRK) patients should not receive any of the current multifocal IOLs, as it would exacerbate the spherical aberration and cause increased glare and halos. In addition, it would be mixing a multifocal cornea with a multifocal lens, which do not work well together. Previous myopic LASIK or PRK patients have increased corneal spherical aberration. In these patients, refractive surprise is more common due to the change in corneal curvature affecting the effective lens position in our current formulas. If a multifocal IOL is to be used in post myopic LASIK or PRK patients, the Tecnis multifocal IOL family would be the better choice, as it corrects the greatest amount of spherical aberration of the current generation of multifocal IOLs.


The good news is that we have options. The bad news is that no one lens can do it all yet. The first step is to match the technology to the patient’s lifestyle. The current multifocal IOLs all have very good distance vision, so the key is to ask which is more important to the patient: near or intermediate vision. The ReSTOR aspheric 4.0 and Tecnis ZMA/BOO both have exceptional near vision, whereas the ReSTOR 3.0/2.5 and Tecnis ZK/LBOO have better intermediate vision than near.

If the patient is a heavy computer user, then the ReSTOR 2.5 or Tecnis ZKBOO have a higher probability of providing spectacle-free usage of the computer. The Tecnis ZMA/BOO patients do very well on the computer without glasses, but it cannot be guaranteed. The ReSTOR aspheric 4.0 patients will not be able to use the computer without moving the monitor toward them substantially. The ReSTOR 3.0 and Tecnis ZLBOO are a good compromise between computer and reading vision. This is easily explained when looking at the different IOLs’ working distances.

Table 16-1

Multifocal/Accommodating Optimized IOLMaster Constants


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Apr 7, 2019 | Posted by in OPHTHALMOLOGY | Comments Off on Multifocal Implants

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