1 µm axial resolution polarisation sensitive OCT system delivered by GALAHAD project with a range of new OCT products

Co-ordinated by G&H Torquay, the project brought together ten partners from across Europe with the common objective of developing hardware, software and know-how to improve the early screening of glaucoma.

GALAHAD finished on schedule at the end of November 2019. Over the last 36 months the project has had a major impact on the development of ultra-high resolution polarisation sensitive optical coherence tomography (UHR-PS-OCT), from advances in components to automated algorithms to process the results. GALAHAD has been very successful in developing components, sub-systems, operational systems (1 µm axial resolution), processes and software related to OCT and has achieved some important results in applying them to glaucoma screening.

The key advances include:

Hardware for UHR-PS-OCT

Components (already available as products from G&H)

• G&H has set the new state-of-the-art in both SM and PM broadband fused fiber components and has a wide range of new products already on the market
• PM and SM collimators
• SM and PM delay lines
• Motorised polarization controller
• Variable dispersion compensator

Sources (products planned to be released in 2020 by NKT)

• NKT Photonics has developed the first polarised supercontinuum source with a long lifetime and robust polarisation extinction ratio (>25 dB PER for >2200 h successful operation)
• Technical University of Denmark (DTU) made fundamental advances in the understanding of noise processes in supercontinuum sources

Spectrometers (customized products available from Ibsen Photonics)

• Ibsen has improved its technology from the large area etch process for its gratings to improved thermal stability for its spectrometers

Software for UHR-PS-OCT

DTU developed numerical all-depth OCT dispersion compensation software

Universitat Politècnica de València (UPV) developed algorithms which set the new state-of-the-art in several areas:

• Retinal layer segmentation algorithms for in vivo and ex vivo rodent OCT images
• Computer-aided diagnosis algorithms for glaucoma from human OCT images
• Epidermis and hair follicle segmentation algorithms for human skin OCT images
• Gloucestershire Hospitals NHS Foundation Trust has made available a large anonymised human glaucoma OCT database

Standards for UHR-PS-OCT

University of Münster (WWU) delivered permanent tissue-like test standards for UHR-PS-OCT testing

WWU reported the first measurement of retinal refractive index as a function of wavelength

Systems for UHR-PS-OCT

Optos assembled two final systems which were characterised with axial resolutions of 1.25 µm (GALAHAD-1) and 1.39 µm (GALAHAD-2)

Preliminary observations with the GALAHAD UHR-PS-OCT systems

>150 OCT measurements from various glaucoma models were performed

• GALAHAD standard mouse retina models at WWU
• Standard test targets and in vivo rodent retina models at the Rigshospitalet, Copenhagen
• Thanks to excellent progress and efforts at Optos, it was possible to demonstrate the systems on a human volunteer

This work has already contributed to analytical procedures for the refined analysis prediction of visual field characteristics by Rigshospitalet

Demonstration of GALAHAD UHR-PS-OCT system

This live demonstration, on a human volunteer, formed part of the workshop on 8 January 2020 to an audience of researchers and clinicians

This went significantly beyond the planned project scope and was a highly satisfactory conclusion to the project.

This project has received funding from Horizon 2020, the European Union’s Framework Programme for Research and Innovation, under grant agreement No. 732613.