Accommodation restoration: When will it be clinically available?

Take-home:

The goal of restoring accommodation in presbyopic eyes with femtosecond laser treatment seems to be getting closer.

Dr. Krueger

By Nancy Groves; Reviewed by Ronald R. Krueger, MD

Cleveland-Clinical trials of the first commercial system for restoring accommodation in the crystalline lens with femtosecond lasers began 2 years ago.

However, it is uncertain how soon this technology will be clinically available for correction in presbyopic patients, said Ronald R. Krueger, MD, who has been working on the concept for nearly 20 years.

The technology is a “promising dream,” said Dr. Krueger, medical director, Department of Refractive Surgery, Cole Eye Institute, and professor of ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland.

“We need to first continue our clinical studies with the more refined commercial laser, having started 2 years ago with the prototype device,” Dr. Krueger said. “Then, we need a better understanding of the internal mechanisms of accommodation so we can develop a safe and effective treatment algorithm. Overall, our technology needs to get better and overcome some of the initial limitations.”

Dr. Krueger is a consultant for Alcon Laboratories and also a co-founder and consultant of LensAR. Both companies are involved in femtosecond laser for cataract surgery, but only LensAR is currently developing femtosecond laser technology for presbyopic correction, he noted.

Research and experimentation

Based on years of research and experimentation on cadaver eyes and in animal, the first clinical trials were performed by Harvey Uy, MD, in the Philippines in late 2011. Through this research, Dr. Krueger is convinced that accommodation can be restored without causing significant lens opacities.

“Reliable and significant accommodation restoration is theoretically possible and clinically promising with femtosecond laser lens treatment,” Dr. Krueger said. “In the absence of any cataracts and significant symptoms, it certainly warrants further testing with the commercial system being used in laser cataract surgery and with new laser patterns to see if we can get clinical efficacy in restoring accommodation.”

The primary concept dates back to an article published in 1998 on the feasibility of using short-pulse lasers to create greater flexibility in the crystalline lens as a prelude to restoring accommodation. This early testing led to a finite element treatment model and additional mechanical testing on human cadaver lenses, in which it was learned that a 2.22 to 8.5 D of change in power could be achieved.

Next, a primate study found no progressive cataract formation even when the animals were treated at high-energy levels (energy 25 to 45 µJ/pulse and 2.0 to 11.3 M pulses per lens).

An Nd:vanadate picosecond laser (10 ps) with prototype delivery system was used in this study and a subsequent phase I clinical trial at the Asian Eye Institute in the Philippines in late 2009 and 2010. In the first series of 5 eyes, one patient had 1.62 D of objective accommodation after treatment; two had about 1/4 to 3/4 D of objective accommodation, and the remaining two had no change.

In the subsequent phase of the clinical trial, 80 presbyopic patients were treated unilaterally with a range of treatment algorithms (energy 10 µJ/pulse and 0.45 to 1.45 M pulses per lens). All subjects had ≤ Grade 2 cataract and had already elected to have lens replacement surgery after a follow-up of at least 1 month following the laser application.

Dense patterns of bubbles appeared in some eyes after surgery but later resolved. No progressive opacity was observed among the eyes with only 1 month of follow-up, and even in one patient who postponed the lens replacement surgery for up to 18 months following the laser treatment.

Patients whose eyes experienced laser-induced gas bubbles in the visual axis reported the most severe visual side effects, but these symptoms abated as the bubbles cleared.

The change in objective accommodation in subjects who improved over baseline was a mean of 0.62 D at 1 month in 51% of the subjects. The change in subjective accommodation was similar, 0.70 D in 58% of patients, although one patient improved by 3.62 D. The mean improvement in best distance-corrected near visual acuity at 1 month was 6 letters in 42% of patients, and the maximum was up to 5 lines.

For his 2012 American Ophthalmological Society thesis, Dr. Krueger described his work to date and concluded that laser disruption could cause pinpoint micro-opacities but not progressive cataract, although it would be preferable not to have any pre-existing cataract.

He also noted that it was unlikely that the laser treatment would lead to vision-threatening cataract, but to achieve this, the center of the crystalline lens should be avoided to minimize any symptoms generated from the pinpoint opacities that were otherwise reported in this group.

Getting closer

Though these studies were performed with a prototype laser in the picosecond range, a commercial system has been approved for equivalency within the femtosecond range to refine laser delivery, Dr. Krueger said. The first procedure performed with the LensAR femtosecond laser took place in Birmingham, England, last fall.

Sunil Shah, MD, performed the procedure in a 50-year-old patient with high hyperopia with astigmatism. As a result, there was a small change in refraction, and uncorrected visual acuity improved from 12 letters preoperatively to 27 letters 1 week postoperatively.

Another group of investigators is also working on restoration of accommodation by laser surgery, using a three-dimensional intralenticular cutting system that creates sponge-like compression joints and sliding joints. Omid Kermani, MD, Rudolf F. Guthoff, MD, and Holger Lubatschowski, PhD, conducted a study of 30 eyes at two sites in Germany.

Using wavefront-sensing and optical coherence tomography, the investigators have been able to document some additional power change and change in thickness of the lens during accommodation, Dr. Krueger said.

Ronald R. Krueger, MD

P: 216/445-8502

E: krueger@ccf.org

Dr. Krueger is a consultant for Alcon Laboratories and LensAR, as well as a co-founder and investor in LensAR.

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