October 2018

COVER FEATURE

Revisiting astigmatism
Astigmatism and presbyopia-correcting IOLs


by Liz Hillman EyeWorld Senior Staff Writer


A patient with keratoconus would not be a good candidate for premium IOL technology.

Marking the axis for an LRI

LRI being placed at the limbus
Source (all): Michael Patterson, DO


Experts share thoughts on aspects of astigmatism with presbyopia-correcting IOLs

Being a refractive cataract surgeon means correcting patients’ distance vision at the time of cataract surgery, but also often addressing their presbyopia and astigmatic issues as well.
“I correct every patient who has astigmatism in a premium lens cases,” said Michael Patterson, DO, Eye Centers of Tennessee, Crossville, Tennessee. “If they’re going to get premium technologies, they deserve premium astigmatism technology.”
There are nuances, however, to addressing astigmatism with presbyopia-correcting IOLs. How much astigmatism could be left without correction with a multifocal or extended depth of focus (EDOF) lens? When would you use a toric vs. a limbal relaxing incision? Are there eyes in which you would not implant a multifocal or EDOF lens based on the patient’s astigmatism?
Dr. Patterson, Tal Raviv, MD, Eye Center of New York, New York, and Richard Lindstrom, MD, Minnesota Eye Consultants, Minneapolis, shared their thoughts on these and other questions involving astigmatism and presbyopia-correcting IOLs.
EyeWorld: How much astigmatism is tolerable with multifocal and EDOF IOLs before it needs to be corrected?

Dr. Patterson: If you’ve got a multifocal, I think 0.25–0.3 D is all that’s ideal. Some patients can tolerate 0.75 D and they do fine. If they have postoperative astigmatism and the patient is satisfied, I won’t do anything, but preoperatively I am going to go down as low as I can to try to treat with a multifocal.
With an EDOF lens, I think you have a little more give in those patients. The astigmatism seems to be more tolerated due to the nature of the lens and how the lens optics work. You don’t have as many astigmatism problems with this, so I have people who have a half diopter or even a diopter with an EDOF lens postoperatively and they are satisfied, especially if it’s with-the-rule. It adds a little more near vision for them.

Dr. Raviv: The low-add multifocal IOLs perform best when astigmatism is minimized to less than 0.5 D. EDOF IOLs have an increased tolerance for residual astigmatism in my experience, nevertheless, I still want to reduce it significantly. 
Accounting for the lifelong against-the-rule (ATR) shift that will occur in most patients,1 I generally target about 0.35 D of with-the-rule (WTR) residual cylinder for someone in their 50s or 60s and less for older patients. 

Dr. Lindstrom: For WTR and ATR, even 0.25 D astigmatism in any axis degrades the image, but the reasonable target is 0.50 D or less. Residual ATR is the worst.

EyeWorld: Are LRIs/AKs acceptable to perform with multifocal or EDOF IOLs?

Dr. Patterson: I use an LRI on every patient who doesn’t qualify for a toric. If the astigmatism is too low for a toric, I’ll use an LRI. If the astigmatism is too low for an LRI, I’ll shift and make my main incision wound on the axis of that. I make sure I’m dialed in as close as possible.

Dr. Raviv: Yes, the lowest cylinder toric power is 1.5, which treats about 1 D of cylinder on the cornea. Accounting for posterior corneal astigmatism and future ATR drift, I typically will employ femto LRIs for WTR cylinder below 1.5 D or for ATR below 0.4 D. I also peek at the refractive cylinder, especially in a patient over 70; significant ATR cylinder in their spectacles/refraction indicates a more significant amount of posterior corneal astigmatism, and generally a higher power toric will be indicated.

Dr. Lindstrom: Yes, but I prefer to use a toric IOL or for small amounts of astigmatism on-axis incisions. LRI and AK have poor long-term stability and induced higher order aberrations. If needed, a PRK or LASIK works well for residual astigmatism.

EyeWorld: What presbyopia-correcting toric IOLs are available and at what range? What has been your experience with them?

Dr. Patterson: Currently, I use the Tecnis Symfony toric (Johnson & Johnson Vision, Santa Ana, California), the AcrySof ReSTOR lens (Alcon, Fort Worth, Texas), Crystalens (Bausch + Lomb, Bridgewater, New Jersey), and Trulign toric (Bausch + Lomb). At this point I use every one on the market at the routine.
I am going to use a toric in every patient who qualifies, who desires to pay for it. But after you get past that, how do you know what lens? If a patient has macular disease, epiretinal membrane, a small set of drusen, I tend to tell them you don’t need a multifocal lens, you either need a Symfony or a Crystalens. If that patient says I can’t handle any side effects, the purest vision they’re going to get is with the Crystalens, but they won’t get as much reading vision. If the patient says, “I want a little more reading,” and they’ve got a small amount of microaneurysms in the macula from diabetes, I’m not opposed to putting in a Symfony lens in those patients. … If a patient desires close reading vision, I’m not going to use an EDOF or an accommodating lens, I’m going to use a multifocal lens.

Dr. Raviv: Today, in the United States, the ReSTOR ACTIVEFOCUS toric, Tecnis Symfony toric, and Trulign toric are available. The cylinder powers available with the toric multifocal IOL/EDOF IOLs are 1.5–3.75 D at the IOL plane, treating up to approximately 2.5 D of astigmatism at the corneal plane. The Trulign toric ranges from 1.25–2.75 D at the IOL plane.
Due to the increased incidence of ATR with aging, it is common to have significant cylinder to treat in the cataract age population. I would estimate that more of my EDOF patients get the toric version over the spherical one. Reducing astigmatism is so important in refractive cataract surgery that I will frequently choose the type of presbyopia-correcting IOL based on the astigmatism present. For example, anyone with 1.25 D of ATR cylinder or greater would do best with a toric IOL, which rules out the low-add multifocal Tecnis ZLB00 and ZKB00, which are only available in spherical powers.

Dr. Lindstrom: I mostly use Symfony toric with good experience. There is a small incidence of rotation, less than 5%. 

EyeWorld: Are there patients with corneal cylinder in whom you would not put a multifocal or EDOF IOL? What about cases with irregular astigmatism or keratoconus?

Dr. Patterson: I’m not going to put a premium lens in someone with corneal pathology because, in my opinion, that means the cornea will not tolerate a premium technology in the first place. ... If you use a premium lens and you can’t use an LRI or toric option, to me there is something wrong with the cornea and you shouldn’t be doing it.
Irregular astigmatism, astigmatism that is a pellucid marginal degeneration, some sort of keratoconus patient, I won’t use it on. Any patient who has severe keratopathy, such as map-dot-fingerprint that has not been treated, Salzmann’s nodule, a herpetic eye patient, I would not use a lot of multifocal lenses in people who have corneal pathology because we know without question their side effects are greater. They have more glare, more halo, and you’re not as accurate in treating their astigmatism.

Dr. Raviv: If their corneal cylinder is irregular, they may not be great multifocal/EDOF IOL candidates but also not toric. Also, patients with cylinder above 3 D will do best with the higher toric power IOLs, which are only currently available with the monofocals. 
If consistent repeatable Ks are achieved on multiple devices, I’m inclined to offer toric IOLs for keratoconus. For irregular astigmatism from pterygium, epithelial basement membrane dystrophy, Salzmann’s, I generally recommend treating the pathology before proceeding with a presbyopia-correcting IOL.

Dr. Lindstrom: I wouldn’t implant diffractive multifocal IOLs in anyone with over 0.5 root mean square of higher order aberration. I also am sure to look for dry eye, which is treatable. 

EyeWorld: What about IOLs in the pipeline, which could be used for both presbyopia and astigmatism correction?

Dr. Patterson: The IC-8 (AcuFocus, Irvine, California) is going to be a game changer. It has distance and near correction, and regardless of the axis that it falls on, the toricity is still going to be corrected.
I’m excited about the AT LISA, which is the trifocal from Carl Zeiss Meditec (Jena, Germany). I’m more excited about the AT LARA (Carl Zeiss Meditec). … The ability to have some sort of accommodative/enhanced depth of focus lens over a multifocal is always going to be a little better because it’s a blended vision. If we can get that a little more optimized, that would be good. I know Symfony 2 is on the way out at some point, and that is exciting. PanOptix (Alcon) should be a great lens. … Juvene (LensGen, Irvine, California) could change some things. The problems with the light adjustable lenses and the refractive index shaping is that these lenses will be more for missing your target rather than a presbyopia correction technology.

Dr. Raviv: The small aperture IC-8 IOL will find utility in complex eyes, such as post-trauma or RK. Its limitations are that it is only indicated monocularly. We are looking forward to post-implantation refractive (including astigmatism) adjustment of IOLs, whether with the Light Adjustable Lens (RxSight, Aliso Viejo, California) or refractive index shaping (Perfect Lens, Irvine, California)—though they will be in monofocal versions initially.

Dr. Lindstrom: I am excited about IC-8, which will be indicated for corneal irregular astigmatism. 

EyeWorld: What do you discuss with patients regarding presbyopia- correcting IOLs in the context of their astigmatism and in terms of setting postop expectations?

Dr. Patterson: I’m very clear to patients that they can’t have it every way. They’re not going to have perfect distance, intermediate, and near, and it’s not going to be like when they were 20. However, we’re going to get their eye seeing the best their eye can see. The only way to do that is to use a lens that can see in multi-ranges with the ability to correct their astigmatism. I think patients respond well to that. If you’re not correcting their astigmatism at the same time for patients who will pay for it, you’re not helping your patients to the best of your ability.

Dr. Raviv: Many patients are surprised to hear they have astigmatism, and I frequently show them their topography and explain that their presbyopia-correcting IOL surgery will include correction of their astigmatism for optimal results. I mention that even with our best diagnostic and surgical technology, residual refractive error (including astigmatism) may remain, and further enhancement treatment with laser vision correction (PRK or LASIK) can be done.
Dr. Lindstrom: I tell them they may need one or two laser enhancements (YAG and excimer), there might be night vision symptoms, and they might need occasional readers, and there will be up to a year of neuroadaption to their new vision. This discussion is the same as with a spherical presbyopia-correcting IOL.

Reference

1. Hayashi K, et al. [Changes in corneal astigmatism with aging]. Nippon Ganka Gakkai Zasshi. 1993;97:1193–6

Editors’ note: Dr. Lindstrom has financial interests with Alcon, Bausch Health (Laval, Canada), and Carl Zeiss Meditec. Dr. Patterson has financial interests with Johnson & Johnson Vision and Carl Zeiss Meditec. Dr. Raviv has financial interests with Johnson & Johnson Vision.

Contact information

Lindstrom
: rllindstrom@mneye.com
Patterson: michaelp@ecotn.com
Raviv: tal.raviv.md@gmail.com

Astigmatism and presbyopia-correcting IOLs Astigmatism and presbyopia-correcting IOLs
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