A Columbian engineering researcher has developed what he claims is a new, non-invasive way to permanently correct vision as an alternative to laser eye surgery.
Sinisa Vukelic claims to have achieved the breakthrough method using something called a "femtosecond oscillator" - an ultrafast laser that delivers pulses of very low energy at high repetition rate. So far, he says, it has shown promise in pre-clinical trials.
The technique is unique because it uses a selective and localised alteration of the biochemical and biomechanical properties of corneal tissue.
It therefore changes the tissue's macroscopic geometry, is non-surgical and should have fewer side effects and limitations compared to refractive laser eye surgeries. For instance, patients with thin corneas, dry eyes, and other abnormalities cannot undergo refractive surgery.
If proven a safe procedure, it could lead to treatment for all major sight issues, such as myopia, hyperopia, astigmatism, and irregular astigmatism, without the need to even touch the patient.
"We think our study is the first to use this laser output regimen for non-invasive change of corneal curvature or treatment of other clinical problems," said Vukelic.
His innovative new method uses the femtosecond oscillator to alter biochemical and biomechanical properties of collagenous tissue without causing cellular damage and tissue disruption. This technique allows for enough power to induce a low-density plasma within the set focal volume, but does not convey enough energy to cause damage to the tissue within the treatment region.
"We've seen low-density plasma in multi-photo imaging where it's been considered an undesired side-effect," added Vukelic. "We were able to transform this side-effect into a viable treatment for enhancing the mechanical properties of collagenous tissues."
The critical component to Vukelic's approach is that the induction of low-density plasma causes ionisation of water molecules within the cornea.
This ionisation creates a reactive oxygen species, that is, a type of unstable molecule that contains oxygen and that easily reacts with other molecules in a cell. This in turn 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.
When this new technique is applied to corneal tissue of the eye, the crosslinking alters the collagen properties in the treated regions, and this, ultimately, results in changes in the overall macrostructure of the cornea.
The treatment ionises the target molecules within the cornea while avoiding optical breakdown of the corneal tissue. Because the process is photochemical, it does not disrupt tissue and the induced changes remain stable.
"If we carefully tailor these changes, we can adjust the corneal curvature and thus change the refractive power of the eye," said Vukelic.
"This is a fundamental departure from the mainstream ultrafast laser treatment that is currently applied in both research and clinical settings and relies on the optical breakdown of the target materials and subsequent cavitation bubble formation."
Vukelic's group is currently building a clinical prototype and plans to start clinical trials by the end of the year. 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 personalise the treatment. It could be that they could scan a patient's cornea and then use Vukelic's algorithm to make patient-specific changes to improve his/her vision.
"What's especially exciting is that our technique is not limited to ocular media - it can be used on other collagen-rich tissues," Vukelic added. "We've also been working with Professor Gerard Ateshian's lab to treat early osteoarthritis, and the preliminary results are very, very encouraging. We think our non-invasive approach has the potential to open avenues to treat or repair collagenous tissue without causing tissue damage."
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