MHz OCT: Why faster is better

OCT has come a long way since its introduction but there is still room for improvement.

OCT has come a long way since its introduction but there is still room for improvement. Dr Aljoscha Neubauer discussed the history of OCT and how he believes it’s future lies in scanning speed in May's print issue of Ophthalmology Times Europe.

According to Dr Neubauer, despite the leaps forward in OCT technology there are still several shortcomings that need to be addressed.

Speed is still an issue. Even though there was an increase between time domain and spectral domain technologies, the latter capable of scan speeds of 20,000 to 50,000 A-scans per second, the current technology still does not allow for dense OCT cubes of the posterior pole to be obtained without lengthy examinations and/or eye tracking. “Moreover, there is still the need to predefine scan protocols for each individual patient," said Dr Neubauer.

To overcome this many surgeons simply consider the posterior pole imaging to be separated into retina and glaucoma sections. However, Dr Neubauer stresses that these predefined areas seem to be technically mandated rather than being based on disease and anatomy.

A further issue to consider in Dr Neubauer's opinion is the quality of the fundus images, which can be unsatisfactory if obtained with infrared alone.

Looking to the future, Dr Neubauer believes that ophthalmic OCT technology may move away from spectral domain based systems towards wavelength swept source ones. In particular, he describes Fourier domain locking (FDML) lasers.

An advantage of this technology is the scan speed, which is in the megahertz range. This speed enables imaging to be performed of the complete posterior pole within one 3D dataset and with dense isotropic sampling in the X-Y plane.

This ability means that the need to predefine a region of interest before the scan will be eliminated. "This also enables new analysis protocols to be defined and may provide advantages in segmenting layers," said Dr Neubauer. Additionally, for patient follow up the corresponding 3D volumes can be easily matched rather than needing eye-tracking as with current technology.

In summary, Dr Neubauer stated, "Generating one high-density 3D dataset covering the complete posterior pole including optic disc and macula region, all in less than one second, appears compelling."

If you would like to learn more about MHz OCT, see Dr Neubauer's full article in the May print issue of OTEurope.