Posted: Wednesday, December 10, 2014

Brillouin optical microscopy, a novel technology for non-contact in vivo measurement of tissue biomechanical properties, is generating considerable excitement because of its possible utility in numerous applications in ophthalmology.

Speaking in London at the 5th EuCornea Congress, Michael Mrochen PhD discussed the promise of Brillouin optical microscopy for understanding and improving outcomes of corneal crosslinking (CXL).

“A variety of tools have been developed for in vivo evaluation of corneal biomechanics. However, as a limitation, they all involve application of a mechanical force which itself induces a change in the highly viscoelastic cornea that confounds the ability to determine the properties of the tissue in its physiological state,” said Dr Mrochen, IROC Science, Zurich, Switzerland.

“Brillouin optical microscopy does not cause mechanical deformation and holds promise to fulfil an unmet medical need by providing more accurate quantitative biomechanical measurements of the cornea and other ocular tissues.”

Brillouin scattering is a phenomenon that arises from the interaction between incident light and acoustic phonons present within the illuminated material.

The Brillouin-scattered light is characterised by a frequency shift that is related to the material’s elastic modulus and depends on the mass density, the optical wavelength and the refractive index. In Brillouin optical microscopy, Brillouin-scattered light is captured with a spectrometer and the Brillouin spectrum is analysed by custom software to determine the Brillouin frequency shift.

Now, after obtaining exclusive licence to commercialise scientific patents created at the University of Rostock, Germany, Avedro (Waltham, Massachusetts, US) is developing a Brillouin optical microscopy system for clinical use. A beta version is expected to be available in the middle of 2015.


Evaluating the effects of CXL

Dr Mrochen reported that findings from ex vivo studies conducted by Scarcelli et al and by Avedro researchers demonstrated that Brillouin optical microscopy was sensitive enough to detect differences between porcine corneas treated using different CXL protocols. The results showed there was a linear relationship between increasing the UVA energy dose and the measured increase in Brillouin modulus after crosslinking.

Scarcelli et al also reported using Brillouin optical microscopy for in vivo evaluation of the human eye and identified differences between keratoconic and normal corneas, as well as within and outside the area of the cone in the keratoconic specimens.

Although more research is certainly needed to establish the clinical role of Brillouin optical microscopy in various applications, Dr Mrochen said that one goal would be to integrate the information it provides with that of corneal topography to design a customised CXL treatment plan for eyes with keratoconus.


Michael Mrochen: