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Lens option can correct for surgically induced astigmatism or an inaccurate position.
Reviewed by John Berdahl, MD
The Light Adjustable Lens (LAL; RxSight) is the first adjustable IOL that facilitates office-based optimization of vision after lens implantation and healing.
The availability of this technology overcomes limitations of the preoperative and intraoperative prediction processes, according to John Berdahl, MD, a partner at Vance Thompson Vision in Sioux Falls, South Dakota.
No matter how much imaging and analysis are done preoperatively or the degree of sophistication of the intraoperative tools, postoperative refractive surprises still happen after cataract surgery despite the surgeon’s best attempts.
After IOLs have been implanted, patients still do not achieve target vision.
When using the LAL, Berdahl estimated that 70% of patients achieved uncorrected distance visual acuity (VA) of 20/20 or better, 92% of 20/25 or better, and 98.7% of 20/32 or better versus 36.3%, 60.6%, and 79.8%, respectively, with a standard IOL. The same type of results were seen with cylinder.
According to Berdahl, LALs offer a more predictable way to provide premium cataract surgery.
The beauty of this system is that although adjustments are made postoperatively, they are not “locked in” immediately. Patients can test-drive different refracts and choose what works best.
The technology allows small tweaks in residual sphere and cylinder errors and can optimize blended vision to achieve excellent vision at all distances. This ultimately results in fewer LASIK enhancements and IOL exchanges.
The components of the LAL system are the lens itself, the insertion device, and the light delivery device.
The LAL is a photo-reactive ultraviolet (UV)-absorbing, 6-mm, biconvex, silicone lens with a rounded-edge anterior surface and a squared-edge posterior surface.
The polymethylmethacrylate haptics are 13 mm in total diameter. The lens is implanted into the capsular bag through a 2.8-mm incision during a standard cataract surgery.
After implantation, light is delivered to the lens causing the macromers in the light path to undergo photopolymerization. Macromers that are untouched by the light then move into the exposed area, causing a precise shape and power change.
Once the desired refraction is achieved, all the remaining macromers are locked in and polymerized.
The light delivery device includes an anterior-segment biomicroscope, a patient chin and headrest, computer for planning and performing light treatment, and UV light-projection system.
The device can treat sphere ranging from - 2.00 D to +2.00 D and cylinder from - 0.50 to - 2.00 D during 1 treatment session.
However, the caveat is that the extremes of the treatment capabilities will not be reached with subsequent treatments.
Berdahl advises that the treatment overall is predictable between -3.00 D and +3.00 D and up to approximately 3 D of astigmatism.
Patient selection is key to achieving high patient satisfaction. Patients may be good candidates if they want to optimize their vision and outcomes, can keep the needed 2 to 4 appointments for light adjustments, have preexisting corneal astigmatism of 0.75 D or more, and can comply with wearing UV protective lenses until after the final light treatment.
Berdahl advised checking for photosensitizing medications preoperatively.
Patients who are not good candidates include those taking systemic medications that can increase sensitivity to UV light, those with a history of ocular herpes simplex virus, those who cannot maintain steady fixation during light treatment, and those who will not wear protective UV glasses after implantation.
For successful surgery, a large pupil of at least 6.5 mm (Berdahl prefers 7 mm) is needed, and Berdahl advised using the A-constant of 118.4.
Following cataract surgery, the patient must wear UV protective glasses, both dark and light.
Patients are instructed to keep the glasses on during waking hours until about 24 hours after they complete the final light treatments. Exposure to UV light, can cause uncontrolled changes to the LAL.
Because of the short intervals between the light treatments, the implantations should be done as close together as possible.
In his practice, Berdahl does implantations on the same day or the second one the next day. Light treatments can be done simultaneously.
The first treatment should be done about 3 weeks following cataract surgery and after the residual refractive error has been determined using a standard phoropter. Having a stable refraction is imperative.
The refractive error then is entered into the light delivery device. The treatment takes about 90 seconds to perform.
The second light treatment should take place at least 3 days after the initial light treatment. If additional treatments are needed, there should be at least 3 days after each previous light treatment.
Berdahl advised a trial of monovision near-point and when adjusting the vision, dialing it in to the place where the patient uses that vision most frequently. He estimated that the entire process takes 5 to 6 weeks.
“In the clinical trial of the LAL, about twice as many patients get 20/20 or better uncorrected VA,” he concluded. “There is a dramatic reduction in outliers defined as 20/30 or worse results from more than 15% to less than 1%.
John Berdahl, MD
This article is adapted from Berdahl’s presentation at the Ohio Ophthalmological Society 2021 virtual annual meeting. He is on the medical advisory board of RxSight.
1. P160055: summary of safety and effectiveness data (SSED). FDA. November 22, 2017. Accessed May 17, 2021. https://www.accessdata.fda.gov/cdrh_docs/pdf16/P160055B.pdf
2. Hangerer F, Srinivasan S, Dick B. Visual outcomes after cataract surgery following bilateral implantation of a postop adjustable intraocular IOL. Presented at: American Academy of Ophthalmology Annual Meeting; October 12-15, 2019; San Francisco, CA.