The new landmarks, findings and signs in optical coherence tomography

Spectral domain optical coherence tomography (SD-OCT) is a useful non-invasive imaging method which is used in the diagnosis and follow-up of various macular diseases. Photoreceptor disruption detected with OCT might be demonstrated the loss of integrity or absence of external limiting membrane, ellipsoid zone and interdigitation zone. It has been considered that the disruptions of these outer retinal layers or zones are highly correlate with lower visual acuity in various retinal diseases. Newly, current OCT findings and signs include outer retinal tubulation, hyperreflective dots/spots, flyer saucer, perifoveal cupping, focal choroidal excavation, dipping sign, choroidal macrovessel, pearl necklace sign, cystoid foveal degeneration, outer retina-choroid complex splitting, foveal pseudocyst, domeshaped macula and brush border pattern. These might be important indicators for prognosis and response in various macular diseases. Introduction Spectral domain optical coherence tomography (SD-OCT) is a very useful non-invasive imaging method which is used in the diagnosis and follow-up of diseases involving the macula, such as age-related macular degeneration (AMD), diabetic maculopathy, central serous chorioretinopathy (CSCR), epiretinal membrane (ERM), various macular dystrophies/maculopathies and macular hole, etc. It provides detailed information for the evaluation of drusen, intraretinal/subretinal hemorrhage or fluid and detachment of retina pigment epithelium (RPE) or retina [1-4]. OCT can reveal ERM, choroidal neovascular membrane (CNVM), fibrovascular lesion, fibrotic scar, hard exudate, nerve fiber infarct and macular or optic disk drusen, intraretinal or subretinal fluid and cystoid cavities [1-4]. These common OCT findings are well known. Currently, due to the developments in OCT technology and the frequent use of OCT in ophthalmology, currently, some new OCT findings have been reported day after day. The aim of this study is to present new pathological or abnormal findings in SDOCT and to emphasize the causes of these. Normal OCT findings and histological landmarks In a normal colored spectral domain OCT scan, the high reflectivity signals represented by yellow and red colors, come from the retinal nerve fiber layer (RNFL), plexiform layers, internal limiting membrane (ILM), junction between inner and outer segments of photoreceptors (IS/OS), RPE and choriocapillaris complex. The low reflectivity signals represented by black and blue colors belong to the nuclear layers. The normal vitreous gel is not visible in color OCT imaging because it is optically transparent and it seems black color (Figure 1) [1,2]. The external limiting membrane (ELM) (Figure 1A) is located at the boundary between the nuclei and the inner segments of the photoreceptors, and points out the junctional complexes between Müller cells and the photoreceptors [1-4]. The ellipsoid zone (EZ) (Figure 1B) is considered to be formed mainly by mitochondria within the ellipsoid layer of the outer portion of the inner segments of the photoreceptors. However, it was previously Correspondence to: Burak TURGUT, MD, Associate Professor of Ophthalmology, Fırat University, Faculty of Medicine, Department of Ophthalmology, 23119, Elazig, Turkey, Tel: Tel: +90 424 2333555; Fax: +90 424 2388096; E-mail: [email protected]