![]() However, the study was limited to optic disc perfusion measurement and the reliability analysis was based upon data from a small number of subjects. reported that OCTA showed a low intra-visit and inter-visit flow index variability. Despite the new knowledge about potential OCTA applications, there is little published data on the consistency and reliability of OCTA. An imaging modality with good repeatability and reproducibility is therefore a prerequisite in deciding if the modality can be relied on in disease management. In clinical practice, repeated posterior segment imaging is often required in diseased eyes in order to detect progression or to monitor treatment response. In fact, it has been suggested that OCTA is potentially an alternative to FA in posterior segment imaging. In additional to that, several studies have also utilized OCTA to detect perfusion changes in optic nerve head in multiple sclerosis and glaucoma. A considerable amount of recent literature suggests the useful application of OCTA in retinal and choroidal pathological conditions, including diabetic retinopathy, retinal vascular disease, age-related macular degeneration, central serous chorioretinopathy, and macular microangiopathy such as sickle cells diseases. In addition, the En Face feature of newer OCTA allows the clinician to view the microvascular plexus that are located at varying depths of posterior segment structures. In contrast to FA and ICG, OCTA is non-contact, non-invasive, easy to perform and capable of providing a clear three dimensional image of the ocular microvascular circulation. Optical coherence tomography angiography (OCTA) has emerged as a new innovation in ocular vasculature imaging technology. However, the necessity of using intravenous fluorescein or indocyanine green dye make them invasive investigations with risk of mortality and morbidity. These imaging techniques provide important information about the posterior segment blood circulation and play a central role in the management of retinal and choroidal conditions. Traditionally, the microvascular circulation in the posterior segment is visualized by means of Fundal Fluorescein Angiography (FA) and Indocyanine Green (ICG) angiography imaging systems. In recent decades, posterior segment microvasculature imaging has become an essential tool in the diagnosis and management of many posterior segment conditions. Pathological changes of the microvasculature in the posterior segment are associated with various eye diseases which potentially lead to blindness. The posterior segment of the eye contains a highly complex vascular system. National Healthcare Group Domain Specific Review Board ( NHG DSRB) Singapore. Interpretation of optical coherence tomography angiography should take into account test-retest repeatability of the imaging system. ![]() The optic disc scan, on the other hand, showed a higher coefficient of variation indicating a lower measurement repeatability than macular scan. The vessel density measurement of macular scan by mean of optical coherence tomography angiography demonstrated good repeatability. ![]() Optical coherence tomography angiography is a useful modality to visualise the microvasculature plexus of macula and optic nerve head. Likewise, the coefficient of variation of optic disc scans, for right and left eyes, ranged from 14.3 to 77.4% and 13.5 to 75.3%. The measurement repeatability tests showed that the coefficient of variation of macular scans, for right and left eyes, ranged from 6.4 to 31.1% and 5.3 to 59.4%. For optic disc images, mean vessel density at vitreoretinal interface, radial peripapillary capillary, superficial nerve head and disc segment at the level of choroid were OD 0.084 and OS 0.085, OD 0.140 and OS 0.138, OD 0.216 and OS 0.209, OD 0.227 and OS 0.236 respectively. For macular images, the mean vessel density at superficial retina, deep retina, outer retina and choriocapillaries segment was OD 0.113 and OS 0.111, OD 0.239 and OS 0.230, OD 0.179 and OS 0.164, OD 0.237 and OS 0.215 respectively. ResultsĪ total of 176 eyes from 88 consecutive normal subjects were recruited. Data were analysed to determine the measurement repeatability. Novel in-house developed software was used to count the pixels in each images and to compute the microvessel density of the macula and optic disc. Two sets of optical coherence tomography angiography images of macula and optic nerve head were acquired during one visit. Subjects with normal eyes were recruited. MethodsĬross sectional observational cohort study. This study set out to measure the microvascular density of macula and optic disc by mean of optical coherence tomography angiography and report the repeatability of the vessel density measurements. Despite the potential usefulness of optical coherence tomography angiography in retinal and optic disc conditions, the reliability of the imaging modality remains unclear.
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