A new intraocular lens (IOL) technology allowing for postoperative vision refinement like we have never seen before is now available in the United States. The Light Adjustable Lens (RxSight) is made of an ultraviolet (UV) light-activated macromer that can be reshaped after cataract surgery to fine-tune the refraction. This technology is unique in that the shape and focusing characteristics of the lens can be changed after implantation (weeks to months).
How it Works
An office-based light source called the Light Delivery Device (LDD, RxSight) focuses UV light on different areas of the lens, causing theilluminated macromers to connect with other particles and form polymers. This changes the curvature of the lens to adjust for residual refractive error after cataract surgery. The light-adjustment treatment requires a fully dilated pupil and takes between eight and 120 seconds each session. Once the optimum focal power is achieved, the LDD then “cures” the lens to lock in the optical power. The curing process activates all remaining marcomers in the lens without changing the lens shape, effectively stabilizing the lens.
Post-op Do’s and Don’ts
Although surgical implantation of this lens is no different than any other three-piece IOL, the post-op journey looks quite different. The patient must wear special UV-blocking glasses at all times—both indoors and outdoors—until several days after the lens is “cured,” which might take a few months. This additional step requires explicit patient education, as exposure to incidental UV light could cause the lens to change in an unpredictable fashion or even use up all the potential macromers. Sunglasses, clear glasses and glasses with bifocal adds are given to the patient.
The post-op process may present a significant commitment for the patient, as multiple treatments (two to five) are necessary to fully adjust the lens. At each visit, the patient undergoes a careful refraction and gives feedback about their visual performance. For instance, if they elected for monovision and the eye was targeted at a refractive error of -1.50D, the patient could then ask for the focal point to be moved in (or out) several inches at one of the follow ups.
The treatment does have its limitations. You can only reliably change up to 2.00D of sphere and up to 2.00D of cylinder in the lens. The treatment is based on what the phoropter refraction can achieve, meaning it may not correct irregular corneas and irregular astigmatism as well as you’d hope.
Commercially, there is an aspheric monofocal lens option offered in the United States, meaning patients can be precisely corrected to any focal point in each eye. This technology is currently not available in other forms, but, as the lens can be molded into any shape, the future may hold multifocal and extended depth-of-focus options. An FDA study is now looking into an extended depth-of-focus variation of this lens.