JM -OCT is promising - more comprehensive investigation of pathology in macular degeneration

Multi-contrast imaging using Jones matrix optical coherence tomography (JM-OCT) is a promising new technique for evaluation of eyes with macular degenerative disease, because it allows for simultaneous visualisation of the retinal pigment epithelium (RPE) and chorioretinal microvasculature, according to researchers from the Computational Optics Group at the University of Tsukuba, Japan. At the 2016 annual meeting of the Association for Research in Vision and Ophthalmology (ARVO) in Seattle, USA, Shuichi Makita PhD highlighted the capabilities of JM-OCT by showing images acquired in eyes with age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy and comparing the features with findings from fluorescein angiography, indocyanine green angiography, and fundus photograph. “Fluorescein angiography and indocyanine green angiography are the gold standard tools for detecting abnormal vessels and RPE abnormalities in eyes with macular degeneration, and now, OCT angiography allows non-invasive visualisation of the microvasculature in the posterior eye. However, delineating the location of a vessel relative to the RPE is difficult using the OCT-based method, and it has no sensitivity to RPE abnormalities,” said Dr Makita. JM-OCT can be used to visualise abnormalities in the RPE and vascular structures, and so would provide information that is comparable with the results of the fluorescent angiography techniques. As a non-invasive modality, however, JM-OCT might be considered for more widespread use and perhaps adopted as a screening tool or to conduct more frequent follow-up examinations, he suggested. FUNCTIONAL EXTENSION Multifunctional JM-OCT imaging is a functional extension of OCT that combines swept-source OCT technology with a polarisation multiplexing unit and a polarisation diversity detector. The system detects four OCT signals comprising the “Jones matrix” that represents the optical property of tissues. Dr Makita explained that with a single JM-OCT scan, one could obtain conventional OCT images and vasculature imaging by computing the complex correlation of the Jones matrix. In addition, polarisation uniformity imaging allows detection of the RPE and choroid because polarisation uniformity corresponds to melanin distribution. Birefringence imaging allows visualisation of the distribution of fibrous tissue. “By combining the OCT angiography and distribution of polarisation uniformity images, we can evaluate the depth of the microvasculature relative to the pigmented tissue. Complex correlation is one of the technologies to achieve OCT angiography imaging,” Dr Makita said. The imaging was performed using a laboratory prototype JM-OCT. It has a central wavelength of 1060nm, a scanning speed of 100,000 A-scans/second, and axial resolution of 6.5 microns. Shuichi Makita: makita@optlab2.bk.tsukuba.ac.jp

Tags: Jones matrix, optical coherence tomography