Surgeons seek presbyopia correction without nighttime dysphotopsia, loss of contrast

New developments in technology and technique may enable surgeons to meet patients’ high expectations for vision quality when it comes to presbyopia correction.

Presbyopia management includes excimer laser ablation, femtosecond laser intrastromal correction, multifocal and accommodating IOLs, and intracorneal inlays.

Essentially, the correction of presbyopia involves multifocality, accommodation or increased depth of field (pinhole effect). Multifocality is created directly on the anterior corneal surface or indirectly in the corneal stroma and with multifocal IOLs. All of these may be implemented monocularly. The biomechanical accommodation mechanism cannot be truly replicated, but emerging IOL designs involve processes designed to simulate natural accommodation.

A binocular solution to presbyopia is monovision.

According to Michael C. Knorz, MD, OSN Europe Edition Board Member, the leading methods of presbyopia correction in his own practice are monovision LASIK, the Kamra inlay (AcuFocus) and various multifocal IOLs.

“It already is a standard if you consider monovision as a procedure to correct presbyopia, which it actually is. We have been using monovision for a long time now in cataract surgery,” Knorz said. “For my patients, multifocal IOLs are used in 60% of cases of refractive lens exchange or cataract surgery, as the majority of my patients opt for a refractive procedure which allows them to be spectacle independent.”

Willingness to take a lens-based approach to correct presbyopia is essential for clinical success, Daniel S. Durrie, MD, OSN Refractive Surgery Section Editor, said.

In addition, clinicians should rely on examination results to educate patients and explain the choice of a particular procedure.

“Patient counseling is the whole thing,” Durrie said. “This is elective surgery. Nobody needs it done. You need to make sure that you evaluate patients carefully and talk to them about their options. Then, at the end of it, tell them why you chose the option that you did. I don’t leave people with multiple options at the end of the exam because their eye will tell me, with my experience, which way to go.”

Asphericity and multifocality

Various IOL designs use aspheric and diffractive optics to create multifocality, the creation of multiple focal lengths. PresbyLASIK and femtosecond stromal changes create a multifocality on the anterior corneal surface, which is often complex and not simply aspheric, Jack T. Holladay, MD, MSEE, FACS, OSN Optics Section Editor, said.

“It’s like a pair of Welsh 4-drop cataract glasses or a pair of invisible bifocal glasses,” he said. “You have a gradual increase in power in the lower part of the spectacle lens, which is analogous to the change in the anterior corneal surface, so you have multifocality in which you have real objects at various distances that are in focus.”

Multifocality is a compromise with consequent tradeoffs, such as loss of contrast, mild reduction (a few letters) in visual acuity and, most importantly to the clinician, nighttime dysphotopsia, he said.

“Things that provide multiple focal lengths would include diffractive multifocals that have two different focal lengths. The diffractive IOL is well understood, so it can be designed for any two distances, such as distance and near or distance and intermediate, but not all,” Holladay said. “This is why you must talk to the patient and determine their needs to select the most desirable near or intermediate add to assure a happy patient. The two simultaneous images on the retina (one clear and the other defocused) result in approximately 30% contrast loss.”

Multifocality causes patients to see halos at night and sometimes causes them to complain of glare, particularly in night driving, Holladay said.

“The loss of a few letters in best high-contrast visual acuity and a 30% loss of contrast are often not noticeable in the real world, especially in bright light. But the only treatment of intolerable nighttime dysphotopsias is an IOL exchange, which has limited the penetration of the multifocal IOL to no greater than 5% of the total cataract market,” he said.

Mild monovision, blended vision

Monovision LASIK, a form of presbyopic LASIK, involves correcting one eye for distance vision and the other eye for near vision. Various multifocal ablation profiles are in development, but monovision is significantly more reliable, Durrie said.

Durrie explained the benefits of mild monovision or blended vision, a variant of monovision.

“It’s basically having the dominant eye be plano, no nearsightedness, farsightedness or astigmatism, and having the nondominant eye be somewhere between 1 D and 1.25 D of myopia without astigmatism. The reason for that is that the eyes can blend together. That’s the reason why it’s called blended vision,” Durrie said.

The optical effect of monovision relies on neuroadaptation, Durrie said.

“The different size between the two images at the brain level falls under the threshold that the brain can fuse those images together and come up with a seamless blend between up close and far away,” he said.

Durrie likened blended vision to stereo music. Stereopsis and auditory perception of stereo sound both rely on depth of perception, he said.

“We know that in stereo music, the speakers are playing the same song, but you don’t know which is playing the bass and it sounds great,” Durrie said. “You don’t want the speakers playing two different songs. That would be a lot of monovision with one eye way up close and one eye far away. You also don’t want it flat like mono music, which doesn’t have any depth.”

Durrie described a study in which he and colleagues determined the amount of anisometropia that would benefit vision. The study included 50 plano presbyopes older than 50 years with no cataract. Patients were fitted with a +0.75 D contact lens in the nondominant eye. The patients were given several weeks to neuroadapt to the lens. The patients then received a +1.5 D lens and, later, a +2.5 D lens. Objective and subjective visual function was tested before the study and after adaptation to each lens.

“It was very obvious that their vision dropped off as soon as we went to the strong lens, and they didn’t function as well for tasks at near or distance. They had more subjective symptoms, loss of stereopsis, loss of contrast,” Durrie said. “With the lens that was not powerful enough, they didn’t get enough benefit. They didn’t get any detriment, but they didn’t get benefit, so it was kind of just right in the middle.”

The study showed that neuroadaptation to mild monovision varies widely in different patients.

“Some people adapt in a couple of hours, and some take several months,” he said. “The people that take a long time, it’s not like they see double or they can’t see, but they’ll feel like their eyes are fighting each other, and it sometimes takes some extra office visits to get them to blend. But in our experience, 99% of people will tolerate mild monovision (1 D to 1.25 D) if you let them try it for a year. It does take more chair time, but it’s very valuable.”

Multifocal, accommodating IOLs

“Basically, in terms of lens approaches, there have been iterative improvements in lens design, but at least in the United States, we’re still limited to three FDA-approved presbyopia lenses that are most commonly used,” Jay S. Pepose, MD, PhD, said.

The three lenses approved by the U.S. Food and Drug Administration are the Crystalens AO accommodating IOL (Bausch + Lomb), Tecnis multifocal IOL (Abbott Medical Optics) and AcrySof ReSTOR 3.0 multifocal IOL (Alcon).

Studies have shown the Crystalens to offer the best intermediate vision. The Tecnis multifocal provides an offset of the average corneal spherical aberration and has a near focal point of around 12 inches. The ReSTOR 3.0 provides optimized near vision around 14 to 15 inches, some intermediate vision and good distance vision, Pepose said.

“But it is pupil-dependent, so if you have a patient who has a very large pupil in the dark that doesn’t constrict well with accommodation or the patient works in a low-lit environment, you don’t get some of that dynamic pupillary change that you want to allow the lens to work for near. So, patients with big pupils that never get small might not see up close as much as they would like,” he said. “The Tecnis multifocal is less impacted by variations in pupil size, since the diffractive rings split the light energy evenly between near and far, but all multifocals lose some light energy to useless higher diffractive orders, which can lead to reduced contrast sensitivity.”

The Acri.Lisa bifocal multifocal lens (Carl Zeiss Meditec) provides add power in one sector, Holladay said. The Acri.Lisa is not approved in the U.S.

“It’s not discrete, like a diffractive, where you have actual focal length. It’s just an increase in the power in one sector of the lens that, when the pupil is large, it doesn’t affect the distance image appreciably, but as the pupil constricts, it comes to that area and gives you a little bit of add power,” Holladay said.

Another presbyopia-correcting IOL that has demonstrated good results in Europe but is not yet approved in the U.S. is the dual-optic Synchrony accommodating lens (AMO).

The most sought-after presbyopia correction technology is a lens that changes power, Holladay said.

“The real holy grail is the ability to change the power of the lens so that you don’t have multifocality,” he said.

Pepose echoed Holladay’s statement, noting that change in power relies on mechanisms that mimic natural accommodation.

“It’s clear that, in terms of accommodating lenses, we would probably get more bang for the buck, so to speak, with a lens that would change shape or curvature more than a lens that would rely completely on a change in axial position” Pepose said. “If you had a lens that would actually, reliably change its refractive index and give you 3 D or 4 D of accommodation and not be subject to capsular changes, wound healing and so forth, that would be tremendous. Any lens that would meet those requirements would be a sought-after lens. There’s no question about that.”

Fluidic and electronic lenses

The NuLens (NuLens Ltd.), a sulcus-based implant, consists of a piston activated by the ciliary muscles that pushes a flexible silicone gel through a small hole, forming a bulge that serves as a lens, Pepose said. The accommodative mechanism mimics that of water fowl.

“That’s how they are able to have this tremendous change in accommodation. They need to because they’re up in the air, and they see a fish. They’ve got to dive, then deal with a giant change in refractive index as they get into the water and still not miss where the fish is. They have to suddenly accommodate,” Pepose said.

The FluidVision lens (PowerVision) involves a fluid polymer that flows through soft haptics and channels, Pepose said.

“There’s an internal activator that changes the anterior curvature, so the anterior optic is deformable,” he said.

Elenza is developing an accommodating lens in which an electric current changes the orientation of liquid crystals and creates a high diffraction index. Micro-sensors detect iris contraction and relaxation, accommodation and 
disaccommodation.

“It actually has these microchips, these onboard processors that are pre-loaded with these algorithms that basically learn each person’s unique signature of pupil constriction associated with accommodation. Like a neural net, they learn the speed and pattern of iris constriction during accommodation,” Pepose said.

The Elenza implant changes power based on dilation and relaxation of the pupil, Holladay said.

“It has a sensor and actually can change the power of the lens by sensing the pupil. If you look up close, your pupil gets smaller,” Holladay said. “The circuitry recognizes that and increases power. Then, when you look at distance and the pupil gets bigger, it gets large and it relaxes the power. So, it actually changes the power from the base power to the add power, back and forth, in a way that doesn’t have any multifocality but actually changes the power from distance to near, when you look at distance or look up close.”

Laser corneal shaping

Two laser presbyopia correction methods based on varifocal shaping of the cornea are in development: IntraCor and SupraCor. Neither procedure is approved by the FDA, but both have CE mark clearance in Europe for hyperopic presbyopia.

IntraCor, performed with the Technolas femtosecond lasers (Bausch + Lomb Technolas), provides flapless intrastromal correction to reshape the cornea without incising the corneal surface.

Intrastromal correction, like excimer laser ablation, also creates multifocality and results in a loss of contrast, Holladay said. In addition, intrastromal correction tends to regress.

“Whether you cause contraction of collagen fibers in the corneal stroma and indirectly change the front surface or make that multifocal change directly on the front surface with LASIK or PRK, you still end up creating a multifocal anterior surface, so you get a loss of contrast,” Holladay said. “The reason why not many people are doing that today is because multifocality in the cornea is difficult to remain stable. The collagen fibers and cornea have a memory, and the effect is not a good solution in terms of losing contrast, and it doesn’t last because the cornea regresses over time with either LASIK, PRK or IntraCor.”

SupraCor, performed with the Technolas excimer workstation, uses a similar corneal shape profile as IntraCor but is designed for presbyopia correction in combination with a LASIK procedure. It results in a plus power in the center of the cornea with the objective of low dysphotopsia effects. According to the company, it has been used in more than 14,000 cases so far. Studies for using SupraCor in post-cataract and post-LASIK hyperopia and myopia are under way. SupraCor provides near addition while minimizing the induction of undesired aberrations, according to the company’s website, and similar to IntraCor, enhances depth of field.

Corneal inlays

Inlays create depth of field and significantly enhance near vision, Holladay said. He compared the pinhole aperture of one inlay to that of a camera in terms of optical function.

“If you change that camera to where you open the aperture up wide, to, say, f-stop of 1.2, all of a sudden the only thing in focus is what you’re focused on and everything in front and behind is out of focus. Sometimes, photographers use this to take a portrait picture,” Holladay said. “But when you want to read up close and see at distance, you want the reverse, and that’s what the 1.6-mm aperture (f-stop 14) provides. Its increased depth of field allows you to gain about four or five lines of near vision.”

In addition, inlays produce no nighttime dysphotopsia, Holladay said.

“[The small aperture] actually doesn’t produce a halo at all because the pencil of light is so narrow,” he said. “However, in extremely low-light conditions (candle light), you may not be able to read very small print.”

There are three intracorneal inlay designs under investigation, none of which are approved in the U.S. Two inlays are undergoing FDA trials: the Kamra inlay (AcuFocus) and the Raindrop near vision inlay (ReVision Optics), according to Roger F. Steinert, MD, OSN Cornea/External Disease Board Member.

The Kamra, based on the concept of a pinhole aperture, is currently in phase 3 clinical trials. It is in wide use internationally, especially in Japan, Steinert said.

The Raindrop, made of a proprietary hydrogel-based material, is 2 mm in diameter and provides plus power in the center of the cornea, Steinert said.

Both the Kamra and Raindrop are implanted in the nondominant eye and involve the creation of a corneal pocket with a femtosecond laser, typically an IntraLase (Abbott Medical Optics), Steinert said.

“Basically, it’s equivalent of a partial LASIK flap. I think both companies are pretty much settled on using a femtosecond laser, most commonly IntraLase, to make those pockets,” he said.

International trials of the Raindrop and Kamra have shown promising results, Steinert said.

“The results of the trials internationally have been really positive. Also, the Raindrop is now having a staged release in Europe and Japan, and it’s getting very positive results out in the field. So, it’s not just in investigation any more internationally,” he said. “What I hear from the people using the AcuFocus has been very positive as well. Some enthusiastic users and a few ophthalmologists have been investigators and have gone internationally to put it in, and they’re happy, too. They’re both showing excellent promise.”

The Kamra and Raindrop can be removed and do not involve invasive intraocular surgery, Steinert said.

“You can say that it’s fully reversible in a sense, but it is something that could be removed if later on somebody developed a cataract or even if they just don’t like the optics,” he said. “You can undo it, so that’s a plus for both of these devices as well. It doesn’t involve surgery inside the eye, which is very attractive to a lot of patients.”

The Flexivue Microlens (Presbia) is a 3-mm implant inserted into a corneal pocket. It is made of a hydrophilic polymer similar to the material used to make various IOLs, according to the Presbia website.

“That is also a hydrogel-type material but kind of the opposite of the Raindrop in that you can think of it almost as a donut, so it doesn’t have any power in the center,” Steinert said. “Then it goes to plus power as kind of a ring around the center, then it goes back down to nothing. So, it’s a very different optical approach.”

Corneal inlays may someday compete with monovision as the preferred treatment for presbyopia, Knorz said. In addition, femtosecond laser technology may be applied to soften the lens to restore accommodation, he said. – by Matt Hasson

 

What is your go-to procedure for presbyopia correction: presbyLASIK, monovision LASIK, multifocal or accommodating IOLs, or corneal inlays?

Monovision LASIK, multifocal IOLs are preferred

In the U.S., we do not have access to presbyLASIK or corneal inlays. Thus, I prefer to use either monovision LASIK or multifocal IOLs to correct presbyopia.

For myopic patients without lenticular changes, I prefer monovision LASIK. However, a monovision contact lens trial is desirable before the procedure to ensure the patient can tolerate the anisometropia and to determine the level of myopia that is required for their near tasks.

If the patient has evidence of cataract and/or hyperopia, then lens extraction with a multifocal IOL may be the preferred option. Multifocal IOLs work best when placed bilaterally, but some patients have achieved success with a multifocal IOL in just one eye.

Elizabeth A. Davis, MD, FACS, is an OSN Cataract Surgery Board Member. Disclosure: Davis is a consultant to Abbott Medical Optics.

PresbyLASIK, inlays perform best

I prefer corneal compensation of presbyopia for early and intermediate presbyopes between 45 and 55 to 57 years of age who require no more than 2 D of correction. For patients older than 55 to 57 years, I prefer refractive lens exchange with multifocal IOLs.

I find PresbyMax with the Schwind Amaris especially useful in presbyopic myopes and low hyperopes. I do not treat emmetropes with presbyLASIK. With PresbyMax I can choose between –5 D to +3 D with good results. The binocularity is indeed an advantage. You should select these cases properly, and corneas with abnormal limits of corneal aberrations are not suitable.

Intracorneal inlays are my alternative method for emmetropes who are poor candidates for corneal multifocality. I prefer the Kamra (AcuFocus) because it is easier to center, thanks to the AcuTarget centration device, and works well in properly selected patients. I do not use monovision at this moment but rather Kamra in the nondominant eye, ablating the corneal stroma to the level to leave the patient with – 0.75 D of spherical correction. This allows me to correct about 2 D with the Kamra, which is good even for advanced presbyopes.

My experience with hydrogel implants, particularly PresbyLens (ReVision Optics), is also good, even though centration is more difficult and we do not have technology to center it properly, as with the Kamra. The advantage of intracorneal inlays is reversibility, as we proved in a recent paper. This is, indeed, a great advantage because those who are not happy may be left with slight monovision, an advantage if explantation might occur.

Jorge L. Alió, MD, PhD, is an OSN Europe Edition Board Member. Disclosure: Alió is a consultant to Oculentis, medical investigator for PhysIOL and AcuFocus, and consultant to Schwind.