Assessing cardiovascular diseases through the eye

- Name: Retinal imaging using polarisation-sensitive optical coherence tomography (PS-OCT). A custom-made PS-OCT system will be used in the trial to image the retinas of patients. - The aim of the study is to establish a normative database for low-cost non-invasive screening based on PS-OCT measurement to accurately screen for coronary artery disease (CAD) through the eye. PS-OCT is an extension of standard optical coherence tomography (OCT), a non-contact imaging method that provides high-resolution, three-dimensional images of biological tissues, in vivo and in real-time. The OCT signal depends on differences in the index of refraction of the tissue to reflect and backscatter and it uses low-coherence interferometry to depth resolve the reflections. OCT has revolutionized the sensitivity and specificity of diagnosis, follow up and response to treatment in almost all fields of clinical practice involving primary ocular pathologies and secondary ocular manifestations in systemic diseases like diabetes mellitus, hypertension, vascular and neurological diseases. This trial is designed to reflect the potential of the method as an alternative low-cost and non-invasive screening method to screen for cardiovascular diseases in particular CAD. For the trial, two cohorts of subjects will be recruited. The first cohort consists of patients with CAD who have undergone cardiac computed tomography angiography (CCTA) or Invasive coronary angiography (ICA). The second cohort consists of age- and gender-matched healthy individuals without a history of CAD or cardiovascular diseases. The PS-OCT imaging of the patients is expected to be performed within six months of previous cardiac imaging. - What and how the intervention works: a combination of vessel wall birefringence (as an indication of tissue integrity) and thickness measurement has been used to diagnose hypertension. While the birefringence of the blood vessel walls in patients with hypertension is lower than those without hypertension, the thickness experiences an increase. - The imaging will be done by PS-OCT experts (Hadi Afsharan and Barry Cense who are experienced biomedical engineers, have imaged tens of subjects, and analysed the PS-OCT data of up to 50 eyes.). Participants will be recruited by a cardiovascular specialist, professor Girish Dwwedi and his associated group. - Method of imaging: the participant will be asked to sit in front of our PS-OCT system and look at a fixation target. The target helps to stabilize the eye, and it also points the eye into the right direction so that we can image the largest blood vessels around the optic nerve head. A head and chin rest is also designed in the system so the participant can rest their head while performing the imaging. There are two stages of imaging; one for calibrating our system, and one for recording the images from the retina. Before each stage, we need a few seconds to make sure that the system is aligned and the light beam entering the eye is centred on the pupil, because this provides the best image quality. Furthermore, quick processing will be done after the calibration stage to assure that the image quality is high enough for the analysis to be performed. While in most cases the calibration stage will be done only one time per time, for some patients this stage may be performed twice if the image quality is not sufficient. If the image quality is still not sufficient after repeating the calibration, then the imaging session will be terminated. Based on our experience, we expect that the whole procedure will not take more than 20 minutes. The imaging will be performed at Fiona Stanly Hospital, Perth, Western Australia. - Imaging will be done once for each participant, however, two or more images may be recorded in a single imaging session. There is also no need to monitor participant compliance or adherence to the intervention. - No tailoring, modification or personalised intervention is planned.