PRESBYOPIA ADVANCES

Ronald R Krueger MD

The concept of treating the crystalline lens with an ultra short-pulse laser as a novel method of correcting presbyopia was first proposed by Ronald R Krueger MD, and Raymond I Myers OD, in 1998. Now, because of increased industry interest and advances in technology, this vision may be coming closer to reality.

Speaking at the WOC 2016 in Guadalajara, Mexico, Dr Krueger, of Cleveland, USA, discussed the past, present, and future of this non-invasive procedure that aims to soften and increase the flexibility of the crystalline lens.

Summarising evidence from research conducted so far, Dr Krueger said that reliable and significant accommodation restoration is theoretically possible and clinically promising with femtosecond laser lens treatment. In addition, no significant safety issues have emerged with the techniques used so far, and results are promising from initial clinical evaluations performed using a commercially available femtosecond laser rather than a prototype system.

Furthermore, subsequent to corporate restructuring, there is a renewed focus on developing femtosecond laser crystalline lens treatment for presbyopia correction at LENSAR, the company co-founded by Dr Krueger for the purpose of developing a laser for accommodation restoration, and this application is also being pursued by a second company, ROWIAK, Hannover, Germany.

“Alpheon, which recently acquired LENSAR, has placed the necessary resources and commitment toward the commercial development of laser accommodation restoration. Now, if we can resolve the variability in the results of this procedure to get more consistent outcomes, I believe we will have a technique that might become a commercial product in the future,” Dr Krueger said.

Following proof-of-concept research in human cadaver eyes, safety studies were undertaken to investigate cataractogenesis.

“From these studies, we concluded that localised photodisruption of the lens with the femtosecond laser causes a local cataract, if you consider cataract as any micro opacity, but the cataracts are not visually significant or progressive. We also learned from these studies, however, that the treatment should probably avoid the centre of the lens,” Dr Krueger said.

VARIABLE OUTCOMES

Assessments of efficacy among patients treated with a prototype laser, including measurement of objective accommodation and best distance-corrected near visual acuity (BDCNVA), showed variable outcomes. Average changes were modest, but some outliers demonstrated more dramatic benefit.

“The device that is in commercial use for cataract surgery is significantly different to the prototype system used in the first clinical trial. It has a shorter pulse width, reduced pulse energy that should limit collateral effects, sophisticated lens and anterior segment diagnostic capabilities, and a fluid interface that minimises laser light scatter,” Dr Krueger said.

He reported that in 2014, Sunil Shah MD, in Birmingham, UK, used the commercial laser to treat 20 eyes of patients ages 40 to 55 years. The best results were achieved in eyes that were emmetropic, which comprised about half of the series. Whereas none of the emmetropes had 20/40 or better BDCNVA at 40cm prior to treatment, all achieved that level of vision at one month postoperatively.

In addition, the preferred viewing distance decreased from an average of 45.83cm to 37.17cm. Among the non-emmetropes, the proportion with 20/40 or better BDCNVA increased from 7.7 per cent pretreatment to 38.5 per cent at one month, and the average preferred viewing distance decreased by 4cm, from 50.3cm to 46.3cm.

“Although the results were not quite as good in the non-emmetropes, they were still promising enough to support further study,” Dr Krueger said.

After a pilot trial, ROWIAK sponsored a two-centre study including 30 eyes of patients aged 50 to 65 years. Results from optical coherence tomography and wavefront imaging showed that the treatment resulted in increased thickening of the crystalline lens during accommodation, which was accompanied by increases in refractive power and spherical aberration.

Dr Krueger said that research now under way is trying to determine whether treatment performed closer to the centre can achieve greater lens flexibility and with acceptable safety. He also suggested the idea of obtaining synergistic benefit from combining the lens procedure with a scleral treatment.

Ronald R Krueger: krueger@ccf.org