Corneal and lens-based refractive surgery advancements optimize vision
LASIK, PRK and SMILE can all provide positive long-term vision results, but advancements in corneal and lens-based refractive surgery are enabling the optimization of vision for an even wider group of patients.
Innovation in corneal and lens-based refractive surgery is a tale of two pathways, according to Ronald R. Krueger, MD, chair of the department of ophthalmology and visual sciences at University of Nebraska Medical Center and director of the Stanley M. Truhlsen Eye Institute.
“As technology progresses, it can increase simplicity, speed and safety. But it can also lead to greater complexity. As technology increases, we have more complex solutions for our problems. ... You’d like to say simplicity is always the best, but in some cases, complexity is needed to provide an even more refined product,” Krueger said.
LASIK, SMILE and PRK are all appealing laser refractive surgery options to provide patients greater personalization in their outcomes, Krueger said.
LASIK has an already well-developed market in the United States, while the use of SMILE will likely expand as more commercial entities offer the technology. Currently, Zeiss is the only company in the country offering the technology to perform the procedure.
“SMILE is very common in the rest of the world. Many locations have had access to the technology for over 10 years, and we’ve had it here for maybe 3 years or so,” he said.
SMILE, LASIK and PRK are all excellent procedures that offer patients encouraging long-term outcomes at 1, 5 and 10 years, OSN Cataract Surgery Board Member Audrey R. Talley Rostov, MD, said.
According to a 2020 Journal of Cataract and Refractive Surgery study comparing 1-year outcomes of LASIK, PRK and SMILE at a U.S. military refractive surgery center, all three procedures achieved excellent visual outcomes in terms of safety, predictability, stability and efficacy.
However, SMILE is a great innovation in the laser vision correction space and offers a solution for patients who may not be good LASIK candidates because of concerns about their residual stromal bed. Often these patients can undergo SMILE due to the need to remove less cornea, she said.
“I’ve been very impressed with the femtosecond laser utilized for SMILE. It’s a gorgeous femtosecond laser. The way it’s able to reshape and cut corneal tissue is amazing. I look at SMILE as the next level of innovation when we discuss laser vision correction,” Talley Rostov said.
Optimized wavefront, customized wavefront and topography-guided technologies for excimer laser procedures all have their place in treating refractive errors, especially for patients with aberrated corneas. Topography-guided PRK is a good fit, for instance, in a patient who requires cross-linking for keratoconus. If the patient has enough cornea to perform topography-guided PRK, their vision can be optimized, she said.
“Further refinement to SMILE, such as evolved femtosecond laser technology and the incorporation of iris registration and OCT into our refractive procedures, will be an amazing addition to the market,” Talley Rostov said.
Despite positive outcomes for most patients, SMILE, LASIK and PRK are all corneal tissue-subtracting procedures, which can lead to postoperative dry eye and other symptoms. Laser-induced refractive index change (LIRIC), however, is a refractive correction technology that uses a femtosecond laser to change the refractive index of the cornea without cutting or removing tissue, OSN Optics Board Member Scott M. MacRae, MD, said.
Surgeons use an ultrafast, low-power femtosecond laser specifically developed for the procedure. It affects the refractive index of the cornea, not its shape, to address refractive errors or aberrations. There is no need for flap creation, lenticular extraction or epithelial debridement, he said.
“Rather than changing shape, it just changes the refractive index by changing the density of the cornea. You can basically program it to treat myopia, hyperopia or astigmatism. You can do any pattern you want to correct optics, such as any wavefront pattern,” MacRae said.
The technique can address refractive error, presbyopia and higher-order aberrations not only on the cornea but also on contact lenses and IOLs, he said.
The noninvasive procedure does not damage the epithelium, so patients can undergo the procedure more than once if a refractive correction needs to be made.
A second human trial of LIRIC for corneal modification is scheduled to begin later this year. MacRae predicted the technology will be commercially available in the next 3 to 5 years.
Corneal tissue implantation
Laser vision technology will continue to provide excellent refractive outcomes, but tissue implantation for refractive purposes may prove to be a paradigm shift in the specialty, Krueger said.
No longer do surgeons use only full-thickness corneas for transplants. They now use anterior corneas for deep anterior lamellar keratoplasty and posterior corneas for Descemet’s stripping endothelial keratoplasty and Descemet’s membrane endothelial keratoplasty, Krueger said.
“We’re using the front half of the cornea, the back portion of the cornea, the posterior cornea, so why not just use corneal stroma in the form of lenticules to fortify and strengthen the cornea and add refractive power to that as well?” he said.
A surgeon’s ability to make incisions with a femtosecond laser and create small pockets for implanted tissue may have a dramatic effect on a patient who is farsighted, he said.
A patient younger than 40 years with hyperopia of more than 6 D has few refractive options. Removal of the lens will make the patient lose accommodation, and LASIK will not fully correct the error without compromise, Krueger said.
“But if you can add tissue, you’ll be creating a better optical solution, and the patient will still have their natural crystalline lens,” he said.
If natural corneal tissues can be implanted in a similar fashion as the synthetic FDA-recalled Raindrop near vision inlay (RVO 2.0) to correct presbyopia, it will be much more acceptable. Corneal tissue implantation would result in less reaction and less inflammation and provide a better solution than the Raindrop, he said.
The role of eye banks for this procedure and corneal tissue transplantations for refractive purposes could be pivotal to their success. SMILE lenticules could be “banked” for future transplant procedures, Krueger said.
“You can take SMILE lenticules and save them. If you had a patient who was –10, took the lenticule out, and then turned around and had a +10 patient, you could put the –10 lenticule in the +10 patient. There are a few international surgeons who are doing this already. They are cryopreserving the lenticules and then using them later after taken out of cryopreservation,” he said.
Tissue implantation and refractive procedures will continue to offer patients customized corneal solutions. However, lens-based procedures are also providing patients with evolved choices to correct astigmatism and improved range of vision to help them achieve their optimized vision.
The available multifocal, trifocal and extended depth of focus (EDOF) lenses are incredible pieces of technology that provide customized vision options, OSN Refractive Surgery Section Editor John P. Berdahl, MD, said.
Current lens technologies have set a high bar in the specialty and offer great outcomes, but the true goal is to develop an accommodating lens that mimics the natural lens of a patient in their youth, he said.
“Even though we have great trifocal, EDOF and adjustable lenses, none of these lenses work as well as the ones God gave us when we were 20 years old. If we can develop truly accommodative lenses or lenses that are exchangeable as technology improves, we can continue to raise that bar even higher for patients who entrust themselves to us,” he said.
Despite not being truly accommodative, the Light Adjustable Lens (LAL, RxSight) is gaining traction in the field and gives surgeons a better option to reduce refractive errors after cataract surgery, he said.
Berdahl said he rarely uses monofocal toric lenses in his practice anymore, choosing to offer the LAL at an increasing rate.
“I think it helps because we don’t have to worry about how our patients heal. It takes many factors outside of our control and puts them in our control,” Berdahl said.
The LAL, the only light adjustable lens currently approved by the FDA, is made of a material that will react to UV light and adjust the lens power after cataract surgery. Patients have three to four light treatments over 1 to 2 weeks depending on the amount of adjustment needed.
Appropriate candidates for the LAL are those who want the best distance vision possible, those with astigmatism and those looking for quality monovision, Berdahl said.
The ability to adjust the lens power up to 3 weeks postoperatively provides an advantage over other IOLs, he said.
“Depending on if their surgically induced astigmatism was unpredictable, if their posterior corneal astigmatism wasn’t accurately measured, if their eye happened to be particularly dry on the day the keratometry measures were obtained, all of those things can be short circuited by doing the manifest refraction in the Light Adjustable Lens 3 weeks postoperatively,” Berdahl said.
The LAL was compared with monofocal lenses in a 2019 International Journal of Ophthalmology study, with positive visual outcomes for patients who received the LAL. Twenty-eight patients received the LAL after cataract extraction, while 12 control patients received a monofocal IOL. The study showed 79% of LAL patients achieved 20/20 or better uncorrected distance visual acuity after lock-in with good stability over 12 months compared with 33% of control patients.
Evolution of IOLs
There is no perfect IOL, but the field continues to evolve, and new lenses are being designed to improve range of vision and quality of vision and reduce dysphotopsia, Talley Rostov said.
“We have the EDOF, multifocal and trifocal technologies. Those work pretty well. There’s a lot of happy patients with those technologies in terms of expanding their range of vision, but there still are some dysphotopsias you must contend with. There’s no perfect lens, but our lens choices, our range of vision, they’re improving,” she said.
EDOF lenses are used extensively in Europe, mostly due to the greater number of EDOF options available compared with the United States. The Tecnis Symfony IOL (Johnson & Johnson Vision) works well as an EDOF IOL, but European surgeons are not as enthusiastic about the technology because it does not provide the full range of vision most European patients expect, Krueger said.
“It gives you the distance and mid-range, but maybe not as much near vision. Are there ways of making that better? The same diffractive pattern being used in the Symfony is being hybridized with trifocal lenses,” he said.
Alcon’s AcrySof IQ Vivity IOL, commercially available in Europe and launched in the United States in January, provides modified monovision and extended range of vision with a non-diffractive design. It does not compromise the best corrected vision in each eye, extends depth of focus and could be a successful option in the United States, Krueger said.
The IC-8 IOL (AcuFocus), which is not FDA approved in the U.S., will likely offer patients improved vision with its pinhole technology. The small aperture IOL has an embedded opaque annulus, creating a pinhole in the center of the lens to increase a patient’s natural range of vision, he said.
New technologies to improve toric alignment and improved preoperative measurements have enhanced IOL performance. Better IOL formulas and advanced methods of biometry can provide better visual outcomes, Talley Rostov said.
A surgeon’s treatment is only as good as their measurements. Measuring accurately every time provides optimized vision, she said.
Advances in femtosecond laser technology have also increased accuracy and ease of IOL implantation and orientation. The Lensar laser system allows a surgeon to perform a customized capsulotomy during an IOL procedure, she said.
“It actually allows you to place small notches to create a custom capsule with streamlined software. This allows you to orient a toric lens, either for a monofocal, multifocal or EDOF toric lens, in the correct axis every time,” Talley Rostov said.
The Catalys precision laser system (Johnson & Johnson Vision) was recently granted 510(k) clearance by the FDA for astigmatism management software. The new software minimizes data entry and transcription errors and reduces calculation time and the need for intraoperative aberrometry for toric IOL alignment.
The software allows for enhanced toric alignment without having to resort to manual marking, Talley Rostov said.
Both the Lensar and Catalys have iris registration technology, which compares preoperative images to the images taken at the laser while the eye is docked and automatically compensates for cyclorotation. It also eliminates the need for corneal ink marking, according to a Lensar press release.
These advancements have improved outcomes in the lens-based refractive surgery arena, Talley Rostov said.
“We see so many patients with previous laser correction, either LASIK or PRK, and now they’re having cataract surgery and want a lens-based procedure. They want to have a great refractive outcome. Fortunately, we now have better biometry, improved IOL calculation formulas and advanced methods to measure the cornea and refractive error as well,” she said.
More non-laser vision options
There are other options for patients who are not candidates for laser vision procedures to achieve their best visual outcomes. Presbyopic patients with high prescriptions or thin corneas relative to their prescription are great candidates for an implantable Collamer lens (ICL, STAAR Surgical) or a phakic IOL, Talley Rostov said.
The ICL technology is also used off label for patients with keratoconus, she said.
“When a patient has a significant amount of anisometropia and wants to decrease their myopia, we have the ability to do so and help improve their vision with an ICL. It’s the same with refractive surgery. We want to optimize a patient’s vision, even someone who has other pathologies such as keratoconus,” she said.
EDOF phakic IOLs are easily removed compared with other IOLs if a patient is unhappy with their visual outcomes. Removing and implanting different multifocal IOLs is a difficult process for surgeons and an unwanted procedure for patients, Krueger said.
“We’ve talked about increased simplicity or complexity, and putting in different multifocal IOLs and taking them out is an unhappy process for everyone involved. If you can put something in that’s removable, like a phakic IOL, that adds to the simplicity side of a procedure. It’s more customizable. A patient can try out the lens, and if they don’t like it, it’s not as much of a step to remove it,” he said.
It is now possible to simulate vision with different types of IOLs to take the guesswork out of refractive surgery. The SimVis Gekko (2EyesVision) is a see-through, head-mounted system that provides patients with a real-world experience of presbyopic visual correction, MacRae said.
The simulator allows patients to experience what their vision may be like with a particular IOL, he said.
“It’s like you’re taking an IOL out for a test drive. You can literally look at how much contrast you’ll have, how much glare you’ll have from a headlight or light source shined at you, and it really is amazing technology. Patients can use this before surgery and see what a particular lens will look like, such as an EDOF or trifocal,” he said.
Future IOL technology
Experimental IOL technology is also being developed. An IOL with super magnification and remote reflective technology (SMARRT) is in development and would allow external control of the lens focus with a smartphone. The lens has multiple internal coatings made of semiconductor nanoparticles with tunable reflectivity, potentially changing the path length of a light beam to provide better near or distance vision, Krueger said.
“This is a passive device. It consists of an unmoving structure that is activated or deactivated by a smartphone. The wearer can turn a reflective coating on and off to customize their vision. When you talk about personalization and customization of vision, this fits right into that field,” he said.
Research is also being conducted on a nanoparticle eye drop that would allow for nanoparticles to infuse within the corneal epithelium to change the refractive index. Patients could customize their vision for particular scenarios, such as enhanced distance or monovision, and the effect would last for a day or two while the epithelium turns over and replaces itself, Krueger said.
“You’d have a hand-held laser hooked onto your smartphone. Using an autorefractor app in your phone selects the laser pattern. The laser would make small holes in your epithelium only, and the nanoparticles would filter into those holes and change the refractive index according to whichever shape you desire. It puts titratable control into the hands of the patient,” he said.
The process would be like “refractive Botox,” Krueger said, but could be performed at home without a surgeon’s assistance.
Innovations in the field have helped to make refractive surgery possible for many patients who normally would not be good candidates. Improved measurement capabilities, better procedures, customized LASIK and SMILE, new IOLs and improvements in corneal transplantation techniques have made the optimization of vision possible for many, Talley Rostov said.
- Cimberle M. Femtosecond laser-induced refractive index change may lead to paradigm shift in refractive correction. www.healio.com/news/ophthalmology/20190702/femtosecond-laserinduced-refractive-index-change-may-lead-to-paradigm-shift-in-refractive-correction. Published July 10, 2019. Accessed Dec. 7, 2020.
- FDA approves Light Adjustable Lens from RxSight. www.healio.com/news/ophthalmology/20171122/fda-approves-light-adjustable-lens-from-rxsight. Published Nov. 22, 2017. Accessed Dec. 15, 2020.
- Johnson & Johnson Vision offers new IOL, software for astigmatism management. www.healio.com/news/ophthalmology/20201002/johnson-johnson-vision-offers-new-iol-software-for-astigmatism-management. Published Oct. 2, 2020. Accessed Dec. 10, 2020.
- Manage astigmatism with the strength of Lensar, now with Streamline IV. www.lensar.com/features_confidence.php. Accessed Dec. 11, 2020.
- Moshirfar M, et al. Int J Ophthalmol. 2019;doi:10.18240/ijo.2019.07.08.
- Raindrop near vision inlay recalled. www.healio.com/news/ophthalmology/20190305/raindrop-near-vision-inlay-recalled. Published March 5, 2019. Accessed Dec. 10, 2020.
- Sia RK, et al. J Cataract Refract Surg. 2020;doi:10.1097/j.jcrs.0000000000000203.
- SimVis Gekko. www.2eyesvision.com/es/simvis/. Accessed Dec. 17, 2020.
- Tedesco A. Light Adjustable Lens ‘truly a disruptive technology.’ www.healio.com/news/ophthalmology/20200120/light-adjustable-lens-truly-a-disruptive-technology. Published Jan. 20, 2020. Accessed Dec. 7, 2020.
- For more information:
- John P. Berdahl, MD, can be reached at Vance Thompson Vision, 3101 W. 57th St., Sioux Falls, SD 57108; email: email@example.com.
- Ronald R. Krueger, MD, can be reached at Truhlsen Eye Institute, Department of Ophthalmology and Visual Sciences, 985540 Nebraska Medical Center, Omaha, NE 68198-5540; email: firstname.lastname@example.org.
- Scott M. MacRae, MD, can be reached at University of Rochester Medical Center, 100 Meridian Centre, Suite 125, Rochester, NY 14618-3926; email: email@example.com.
- Audrey R. Talley Rostov, MD, can be reached at Northwest Eye Surgeons, 10330 Meridian Ave. N., Suite 370, Seattle, WA 98133; email: firstname.lastname@example.org.
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