OCT imaging helps show biomechanical changes in tissue after laser surgery

Optical coherence tomography can visualize the tissue structure by IR light scattering with a resolution of up to several microns.

Jan 10th, 2019

Although laser surgery is a very popular tool for correcting various vision disorders, it is still difficult to ensure proper control over the accuracy, efficiency, and safety of such procedures. Recognizing this, a team of researchers from the Institute of Applied Physics at the Russian Academy of Sciences (IAP RAS; Nizhny Novgorod, Russia) used optical coherence tomography(OCT) to help describe tissue changes after such operations.

For the widespread and safe clinical use of lasers for eye surgeries, it is crucial to ensure high-precision control of the given shape of the fabric and its stability. At the same time, it is important to evaluate the accompanying changes in the tissue microstructure and its mechanical properties after laser modification. One of the most promising methods for such applications is OCT, which occupies a niche between medical ultrasound and optical microscopy, as it can visualize the tissue structure by infrared light scattering with a resolution of up to several microns.

The researchers implemented OCT to investigate tissue deformations and mechanical properties changes. The study was conducted on samples of collagen tissue, such as rabbit cornea and pig cartilage, that were subjected to the procedures of localized thermomechanical modification by laser.

"We place the cornea or cartilage sample under investigation between two silicone layers with a known stiffness. Visualizing with the help of OCT the mechanically produced deformations in such a construction, it is possible to quantitatively map the distribution of the elastic modulus of the tissue under investigation, both before and after laser thermomechanical modification," says Vladimir Zaytsev, who led the work.

The results are in good agreement with the data obtained by various methods of microscopy and in theoretical computer simulations. However, OCT does not require special preparation of the drug using dehydration, staining, and other destructive procedures. The developed noninvasive elastographic approach can be used in medicine for the quick assessment of the long-term stability of cartilage implants prepared by laser reshaping, as well as for monitoring the procedures of thermomechanical cornea modification and various diagnostic studies.

"Preliminary results make it possible to count on the promise of using OCT elastography to perform" optical biopsy "of tumor diseases, and not just to distinguish between tissue in the normal state and pathology," Zaitsev concludes.

Full details of the work appear in the Journal of Biophotonics.

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