Extended depth of focus technologies expand presbyopia correction options

Over recent years, multifocal IOL technology has greatly improved, incorporating innovative optical concepts aimed at overcoming the three principal weak points of previous models: reduced contrast sensitivity, photic phenomena and suboptimal intermediate acuity. Extended depth of focus, or EDOF, has entered the scene as a new class of IOLs with a diffractive optic profile that extends the range of vision and at the same time corrects chromatic aberration.

“It is a different principle and technology,” Preeya K. Gupta, MD, an OSN Cornea/External Disease Board Member, said. “Unlike traditional multifocal IOLs, there aren’t two distinct focal points, one for distance and one for near, but rather an elongated focal point that enhances depth of focus, providing an extended range of good vision from distance to intermediate.”

Although EDOF has been a good new addition to the armamentarium for refractive cataract surgery, it is still not a perfect technology and entails some degree of compromise.

“EDOF technology provides good intermediate vision; however, near vision is not as sharp as with some of the new-generation multifocal IOLs. Night vision disturbances are less and not the typical halos, but there are patients who describe something like a starburst or a spiderweb around light sources,” Gupta said.

Patient selection is still the key, and with an enriched armamentarium, there are more chances to hit the target of satisfying patients.

Source: Teresa L. Cartwright, COT

“The more options we have, the more we can refine our ways to understand what patients want, what their goals are and what they are best suited for,” Gupta said.

Differences in technology

According to Damien Gatinel, MD, PhD, there are several ways to address the difference between EDOF and multifocal lenses. On a functional approach, the EDOF IOLs are intended to extend the range of clear uncorrected vision from far to intermediate distance.

“If they are truly making the eye emmetropic, they do not provide sufficient near vision to read comfortably small print, although they may work fine for highly contrasted images such as smartphone screens when held a bit beyond the reading distance and/or their character size is increased,” he said.

On the other hand, multifocal IOLs are aimed at providing full-distance correction — from far to near, encompassing intermediate distance for trifocal IOLs — but because the light is dispersed in more foci than with EDOF, they may lead, at least theoretically, to greater glare and halos.

On a technical approach, there are schematically two optical principles that can be used to design EDOF IOLs.

“Refractive designs are zonal, and specific zones within the IOL optic are dedicated to far and intermediate vision distances. One example is the Lentis Comfort Mplus low add (Oculentis). Diffractive designs, as for the Tecnis Symfony (Johnson & Johnson Vision), use a diffractive element to split light into different foci. According to the manufacturer of the Symfony, the diffractive process incurred by the IOL steps results in multiple foci, which encompass useful distances from far to intermediate vision. In vitro studies have shown us that this type of optic can be quite accurately described by a wavelength-dependent bifocal diffractive split between distance and intermediate vision,” Gatinel said.

Because diffraction is wavelength-dependent, the foci for green, red and blue light are located at slightly different distances, and this creates what manufacturers define as an “elongated focus zone.”

“In our study we found that similar elongation happens around any foci of a diffractive bifocal or trifocal lens. However, the spread of blue to red at the distance foci is different in the Symfony than in other diffractive lenses, hence the ‘chromatic compensation’ effect,” he said.

Patient goals, expectations

Understanding patients’ expectations starts with finding out how strong the motivation is to get rid of spectacles, Gupta said.

“Some patients are comfortable with glasses while other patients do not like them at all. This is something to take into account and to discuss. For example, patients who are low myopes may put on glasses to drive but not for reading. If you do cataract surgery on them and don’t talk about what their goals are, they may be very upset with losing near vision. I spend a lot of time understanding what the patients’ goals are,” she said.

This entails describing the risks and benefits of multifocal and EDOF technology, talking about glare and halos, and trying to understand the patient’s personality type. Those with a Type A personality or anyone who would be bothered by any level of night vision symptoms may not be good candidates for any pseudoaccommodative lens.

“On the other hand, for patients who have realistic expectations, who are highly motivated to be free of spectacles, the technology we have out there is excellent and provides a high level of satisfaction. In most cases, patients tend to tolerate the night glare and halo. The lower power multifocal IOLs that have recently entered the market, such as the Tecnis 2.75 D (J&J Vision) or the ReSTOR 2.5 D (Alcon), have a better night vision and glare and halo profile compared to the higher add power lenses. Patients might not get as robust near vision but are happy with intermediate vision and fare better in night vision complaints and might accept this compromise,” Gupta said.

Targeting vision

Patients basically fall into two groups, according to Hiroko Bissen-Miyajima, MD, PhD. The first group includes those who want clear distance and intermediate vision and accept wearing reading glasses if necessary. The other group includes those who give priority to distance and near over intermediate vision and do not want to wear reading glasses. Those patients can normally accept a slight loss of contrast sensitivity and halos at night.

“If the patient wants good vision without any problem such as loss of contrast sensitivity or glare and halos, I use EDOF, and I tell them that they may need reading glasses. The good news with EDOF is that we can aim for slight myopia, so that the patients can improve near vision,” she said.

Multifocal lenses come with many options for near additions, from 4.0 D to 2.5 D, and this needs careful evaluation of several factors, she said. In Japan, for instance, people like to read newspapers or books at a distance of around 30 cm because they are smaller and have shorter arms than Western people.

“Particularly women like to read and sew at a distance of 30 cm, so for them I would choose a multifocal lens with 4.0 D near addition. Low addition is suitable for those who use computers at a distance of 40 cm or 50 cm. Recently I have shifted to EDOF for those who don’t need high near addition, and for multifocals, I prefer trifocal,” Bissen-Miyajima said.

Because the EDOF Symfony lens was approved in Japan only this year, her experience with this technology involves about 100 cases as compared with the thousands of cases she has implanted with multifocal IOLs over more than 20 years. However, she has had the opportunity to appreciate the advantages of this new option.

“Glare and halo are not zero, but frequency and severity are less. Neuroadaptation does not depend on the type of lens but on the patient. With multifocal lenses, some patients adapt immediately; others need 3 to 6 months. I only started using EDOF IOLs this year, so I do not have sufficient evidence, but up to now not a single patient had difficulty adapting after implantation,” she said.

According to Gatinel, the best indication for EDOF lenses corresponds to a patient whose refractive ambition is to avoid spectacles for distance and intermediate vision, minimizing the risk for night visual disturbances. Typically, these patients have an active lifestyle and/or use the computer frequently.

“If the dominant eye is emmetropic and the nondominant eye is targeted for a slight myopic error (–0.75 D), a mini-monovision effect can increase the spectacle independence for near vision tasks,” Gatinel said.

On the other hand, trifocal IOLs are suited for patients who seek full spectacle independence and have no particular fear or professional contraindications regarding the possibility of halos and glare. These are the lenses he prefers because intermediate vision is satisfactory, maybe not as good as with EDOF, but with no sacrifice of near vision.

Broad range of patients

OSN Cornea/External Disease Section Editor Elizabeth Yeu, MD, used to have a conservative approach when it came to selecting patients for multifocal IOLs. She only implanted them in pristine eyes, with little corneal astigmatism, and often thought that the time involved in the selection and follow-up was too much work to be worth it.

With the introduction of the Symfony EDOF in the past year, the number of presbyopia lenses she implants has increased by two and a half times. In fact, 20% to 25% of the lenses she implants now are EDOF lenses. The high level of satisfaction achieved in both quality and range of vision has guided her decisions to implant Symfony IOLs in her mother-in-law, as well as for the parents of referring optometrists.

“In my opinion, it is definitely the best in class, a leap above the satisfaction level we were able to achieve and for a broader range of patients,” Yeu said. “The contrast sensitivity provided by the Symfony’s optic is so good that it allows us to put it in eyes that are not ideal and not perfect, for instance, eyes that are sufficiently good after myopic LASIK or PRK, and eyes with mild pigmentary mottling in the macula without any subfoveal drusen. I would have definitely excluded some dry eye patients for potential contrast issues and suboptimal patient satisfaction. Now I can offer them this IOL because it has such a high level of quality of vision at multiple ranges. And, of course, there is the toric option for patients with astigmatism,” she said.

“The quality of this optic is as good as, if not better than, certain monofocal IOL optics, which we consider to be the gold standard for contrast sensitivity. This was clinically impressed upon me with a 55-year-old patient who, after very long discussions, implanted a Symfony EDOF IOL in the second eye. She had previously undergone successful cataract surgery with a monofocal IOL in the first eye a few years ago and had an uncorrected distance visual acuity of 20/20. She was a very perceptive woman, and on postoperative day 1 from cataract surgery with the Symfony IOL, she very enthusiastically relayed to me that the quality of color and clarity of vision truly were more defined in the Symfony eye,” Yeu said.

Accurate testing

Selecting the best IOL for individual patients also entails accurate testing, Jay S. Pepose, MD, PhD, said. Particularly for multifocal lenses, topography, corneal wavefront and evaluation of the astigmatism are mandatory.

“Most systems allow us to convert the topography into a corneal wavefront. I use the Zeiss Atlas and look particularly at the horizontal and vertical coma, and if they are over +0.3 µm at the 6-mm zone, I start not being confident about implanting a multifocal. If the cornea is not regularly shaped, the light, by the time it passes through the cornea and hits the lens implant, is already scrambled. This is so much more important with multifocal lenses because the light energy is split between two or three major focal points and the contrast decreases. When you start reducing the contrast, you become much more sensitive to these other aberrations because they also create some ghosting,” he said.

The corneal wavefront should be taken into account when implanting an EDOF lens, but these IOLs are “a lot more forgiving,” he said, because this type of optic takes the whole conoid of light and elongates it.

“So the light might be focused a little bit forward or a little behind, but you are still within the narrowed cone of light,” he said.

The angle kappa is another important factor, which can be measured with the Lenstar (Haag-Streit), the IOLMaster (Carl Zeiss Meditec) or any topography system.

“If you have a big angle kappa, the primary ray of light will not be coming through the center of the pupil but toward the edge. Since IOLs are centered within the capsular bag, that primary ray of light may not go through the central zone of the IOL but transverse the first ring of the multifocal lens, creating a lot of ghosting and aberrations,” Pepose said.

How much angle kappa that can be tolerated depends on the lens that is being implanted, he said. A lens with a small central optical zone requires a tight angle kappa, while a lens like the Symfony, which has a much larger central zone within the first echelette, is going to be more forgiving in eyes with larger angle kappa, more typically seen in hyperopic eyes.

Macular OCT should be routinely performed in patients who are candidates for these type of lenses because even a thin epiretinal membrane, a small drusen or some other subtle macular pathology would lower contrast, and multifocal lenses, by definition, also lower contrast to some extent.

“I also look at the optic nerve by OCT because patients with glaucoma have lower contrast as well,” Pepose said. “With patients who are at a higher risk to develop glaucoma or macular degeneration, for example diabetic patients, patients with a family history of AMD or patients with high IOP, I consider the age factor. Someone who is 55 or 60 years old has a much higher life expectancy than an 80-year-old, so I think in my mind: If this person lives another 30 years and has these risk factors, am I doing a favor to him or her by implanting a lens that could independently lower their [contrast sensitivity] even more if they develop the disease?”

With the Symfony lens, the reduction of chromatic aberration and corneal spherical aberration partly compensates for the loss of contrast due to the splitting of the light into thousands of focal points.

“These two elements of the Symphony optic offset each other, so the [contrast sensitivity] is a little higher than it is with multifocal lenses, and I am a little more willing to implant it in these patients,” Pepose said.

The same applies to patients who have previously undergone corneal refractive surgery.

“They have a multifocal cornea, and if I implant a multifocal lens and it does not line up exactly with the corneal ablation, they could have a tremendous light show at night. As long as the ablation looks centered and the corneal aberrations are pretty symmetrical, I do sometimes implant an EDOF, but I am cautious about multifocal lenses in that setting,” he said.

Mix-and-match strategies

EDOF IOLs have also enriched the range of options for mix-and-match strategies.

Yeu likes to start with a Symfony lens in the nondominant eye and make sure patients are satisfied with vision and quality of vision before she moves forward to the dominant eye. She then decides whether to implant another EDOF or, if the patient is sensitive to night vision symptoms, a standard monofocal.

“Even if they don’t have a perfect reading vision and need correction, they will still be able to look at the dashboard, read texts on their mobiles and utilize the computer. For more extended computer use or book reading, they may need glasses in order to bring the distance sight near,” she said.

For those who are prevalently book readers rather than digital readers, or for those who have short arms, she starts with the dominant eye aiming for emmetropia with a Symfony lens. In the second eye she might implant a mid-add multifocal lens.

In patients with long arms, the situation is reversed because their near vision is somebody else’s intermediate vision.

“If they are satisfied with their dominant eye, I will aim for emmetropia again in the nondominant eye so that I can mitigate night vision symptoms and give them the high quality of vision they are looking for,” Yeu said.

When mixing and matching IOLs, Bissen-Miyajima implants a multifocal with a +4 D add. If distance is a little blurry, she implants either a multifocal with a low add or an EDOF lens in the other eye.

“I don’t plan it a priori, but if it is necessary I do mix and match and the results are usually quite good. In Japan most patients are cataract patients, and usually I start with the eye with more severe cataract. Not the dominant or nondominant eye, but whichever of the two needs surgery sooner. Most of my colleagues say that the dominant eye should get EDOF because distance is clear, but this is not my criterion. First, I ask patients what is more important to them, very clear distance vision without night glare and halo but some loss of contrast or the ability to read without spectacles. Based on their answer, I implant the lens that is more important, and if they have any problem I choose a different lens for the other eye,” she said.

Gatinel does not like to mix and match IOLs of different types. To gain more near vision after an EDOF lens has been implanted, he prefers to implant another EDOF lens, targeting for a slight myopic error.

“Trifocal lenses, on the other hand, provide full spectacle independence at all distances and can be implanted in both eyes provided the patients have no particular fear or professional contraindications regarding the possibility of halos and glare,” he said.

“Personally, I tend to avoid the use of different IOL types in the eyes of my patients, but this approach may prove useful in specific cases,” he said.

Patient complaints

With the new generation of presbyopic lenses, neuroadaptation mostly occurs, quality of vision improves and visual symptoms decrease over time.

“Patients adapt. Imagine you buy a house near the airport. The first week you are bothered a lot by the airplanes, but a couple of weeks later you don’t even hear them anymore. That’s basically what happens,” Pepose said.

When patients complain of severe and persistent vision disturbances, possible causes should be investigated and treated appropriately.

“One thing can be dry eye, so I do tear osmolarity and vital dye staining looking for the evidence, and treat dry eye if necessary. I also look at the lens implant, dilate the patient and carefully examine the capsule because in some of these patients very small amounts of capsular opacity or fibrosis can cause a tremendous amount of glare and ghosting. I have a very low threshold to do YAG in these patients. I do it as soon as I see the early signs of opacification. The next thing I look at is that I have hit the target. I always try to get patients to plano, but if I miss half a diopter or have a little bit of astigmatism and correct what’s left, disturbances go away and night vision gets better. However, if vision is good in daylight but not at night, my advice is to get a thin pair of glasses rather than go through another surgical procedure. I tell my patients to keep them in the car and just use them for night driving. For many patients this is fine and helps,” Pepose said.

Residual refractive error

Management of refractive error after surgery is critical, especially in the premium lens population, according to Gupta.

“Astigmatism as well as residual myopia and hyperopia cause blur, and this can be accentuated by a multifocal lens,” she said.

First is to prevent this from happening by making sure that patients do not have dry eye, that they have a normal, regular topography, and that measurements are repeatable.

“Beware of inconsistencies,” she said.

In her opinion, anyone who implants premium lenses should have skills in refractive surgery, such as LASIK or PRK, to be able to enhance patients when necessary.

“LASIK is an option, but surface ablation is fairly easy to learn and I think that it has a lot of value in terms of managing residual refractive error. If there is a high refractive error, being comfortable with lens exchange techniques is important because at some point laser correction might not be enough. With respect to astigmatism, patients who have a plano spherical equivalent can be managed with a simple limbal relaxing incision at the slit lamp,” Gupta said.

Explantation rate is low, less than 1%, if careful preoperative assessment and patient selection are done, Bissen-Miyajima said.

Fast-growing market

Now that more and better presbyopic IOL solutions are available, and most of them include a toric option, surgeons have seen the demand for this type of lens grow rapidly.

“In my practice, with the combination of EDOF and multifocals, I am close to 60% of patients who ask for one of the two,” Pepose said.

“In my practice, I am up to 80%, which is very high and quite unusual in Japan, where the overall percentage of premium lenses is still 1% because they are not reimbursed by the national health care system,” Bissen-Miyajima said.

“I have a long experience, and many doctors refer patients to me if they have an interest in premium lenses. Many also come through the internet or word of mouth,” she said. “We are currently discussing forms of co-payment with the government, and I believe this will make the market for these lenses expand enormously in our country.” – by Michela Cimberle

• References:
• Attia MSA, et al. J Refract Surg. 2017;doi:10.3928/1081597X-20170621-08.
• Breyer DRH, et al. Asia Pac J Ophthalmol (Phila). 2017;doi:10.22608/APO.2017186.
• Cochener B, et al. J Cataract Refract Surg. 2016;doi:10.1016/j.jcrs.2016.06.033.
• de Medeiros AL, et al. Clin Ophthalmol. 2017;doi:10.2147/OPTH.S145945.
• Gatinel D, et al. J Refract Surg. 2016;doi:10.3928/1081597X-20160121-07.
• Mencucci R, et al. Clin Ophthalmol. 2017;doi:10.2147/OPTH.S142860.
• Millán MS, et al. Biomed Opt Express. 2017;doi:10.1364/BOE.8.004294.
• Monaco G, et al. J Cataract Refract Surg. 2017;doi:10.1016/j.jcrs.2017.03.037.
• Rojas MJ, et al. Curr Opin Ophthalmol. 2016;doi:10.1097/ICU.0000000000000266.
• Ruiz-Mesa R, et al. Eur J Ophthalmol. 2017;doi:10.5301/ejo.5001029.

• For more information:
• Hiroko Bissen-Miyajima, MD, PhD, can be reached at Tokyo Dental College, Suidobashi Hospital, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, Japan 101-0061; email: bissen@tdc.ac.jp.
• Damien Gatinel, MD, PhD, can be reached at Fondation Rothschild, 25 Rue Manin, 75019 Paris, France; email: gatinel@gmail.com.
• Preeya K. Gupta, MD, can be reached at Duke University, Department of Ophthalmology, Box 3802, Durham, NC 27710; email: preeya.gupta@duke.edu.
• Jay S. Pepose, MD, PhD, can be reached at Pepose Vision Institute, 1815 Clarkson Road, Chesterfield, MO 63017; email: jpepose@peposevision.com.
• Elizabeth Yeu, MD, can be reached at Virginia Eye Consultants, 241 Corporate Blvd., Suite 210, Norfolk, VA 23502; email: eyeu@vec2020.com.

Disclosures: Bissen-Miyajima reports she is a consultant for Alcon, AMO, Hoya and Carl Zeiss Meditec. Gatinel reports he has a proprietary interest in the trifocal diffractive optic. Gupta reports she is a consultant for Alcon and Johnson & Johnson Vision. Pepose reports he is a consultant for Bausch + Lomb, Johnson & Johnson Vision and AcuFocus. Yeu reports she is a consultant for Alcon, AMO, Bausch + Lomb and Carl Zeiss Meditec.

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