Columbia team's 'non-invasive' laser method corrects corneal shape

31 May 2018

Low-power, ultrafast laser and photochemical effects alter properties of collagenous tissue without cell damage.

Columbia Engineering researcher Sinisa Vukelic has developed a new non-invasive approach to permanently correct vision that is showing great promise in preclinical models.

The method uses a femtosecond oscillator, an ultrafast laser that delivers pulses of very low energy at high repetition rate, for selective and localized alteration of the biochemical and biomechanical properties of corneal tissue.

The technique, which changes the tissue’s macroscopic geometry, is non-surgical and has fewer side effects and limitations than those seen in refractive surgeries. The study, which Vukelic says could lead to treatments for myopia, hyperopia, astigmatism, and irregular astigmatism, has just been published in Nature Photonics.

“We think our study is the first to use this laser output regimen for noninvasive change of corneal curvature or treatment of other clinical problems,” commented Professor Vukelic, who is a lecturer in discipline in Columbia’s Department of Mechanical Engineering.

His method uses a femtosecond oscillator to alter biochemical and biomechanical properties of collagenous tissue without causing cellular damage and tissue disruption. The technique allows for enough power to induce a low-density plasma within the set focal volume but not enough energy to cause damage to the tissue.

Prof Vukelic added, “We have seen low-density plasma in multi-photo imaging where it has been considered an undesired side-effect. We were able to transform this side-effect into a viable treatment for enhancing the mechanical properties of collagenous tissues.”

The critical aspect of Vukelic’s approach is that the induction of low-density plasma causes ionization of water molecules within the cornea. This ionization creates a reactive oxygen species, which interacts with the collagen fibrils to form chemical bonds, or crosslinks. The selective introduction of these crosslinks induces changes in the mechanical properties of the treated corneal tissue.

The treatment ionizes the target molecules within the cornea while avoiding optical breakdown of the corneal tissue. Because the process is photochemical, rather than physically invasive, it does not disrupt tissue and the induced changes remain stable.

Precise tailoring

“If we carefully tailor these changes, we can adjust the corneal curvature and thus change the refractive power of the eye,” said Prof Vukelic. “This is a fundamental departure from the mainstream ultrafast laser treatment that is currently applied in both research and clinical settings, which relies on the optical breakdown of the target materials and subsequent cavitation bubble formation.”

“Refractive surgery has been around for many years, and although it is a mature technology, the field has been searching for a viable, less invasive alternative for a long time,” says Leejee H. Suh, Miranda Wong Tang Associate Professor of Ophthalmology at the Columbia University Medical Center, who was not involved with the study. “Vukelic’s next-generation modality shows great promise. This could be a major advance in treating a much larger global population and address the myopia pandemic.” .

Future developments

Vukelic’s group is building a clinical prototype and plans to start clinical trials by the end of 2018. He is also looking to develop a way to predict corneal behavior as a function of laser irradiation, how the cornea might deform if a small circle or an ellipse, for example, were treated. If researchers know how the cornea will behave, they will be able to personalize the treatment—they could scan a patient’s cornea and then use Vukelic’s algorithm to make patient-specific changes to improve his/her vision.

“What is especially exciting is that our technique is not limited to ocular media: it can be used on other collagen-rich tissues,” Prof Vukelic adds. “We’ve also been working with Professor Gerard Ateshian’s lab to treat early osteoarthritis, and the preliminary results are encouraging. We think our non-invasive approach has the potential to open avenues to treat or repair collagenous tissue without causing tissue damage.”