Topic

#Imaging

17 articles
  1. Articles 1 Apr 2021 17 min read

    Fundus Fluorescein Angiography and Indocyanine Green Angiography: Made Easy for the Postgraduates

    Introduction and Gross Anatomy: The retinal and choroidal circulatory system can be visualized in vivo in the presence of normal media clarity. Many important diseases of the retina are related to or associated with the changes in the vasculature of the retina and/or choroid. Hence, it is important to understand the circulatory systems involved to better recognize disease states of the posterior segment. The retinal and choroidal vascular anatomy can be basically divided into 3 parts: Retinal and choroidal vasculature Superficial and deep capillary plexus Inner and outer blood-retinal barriers A: Retinal and Choroidal Vasculature: The retina receives its nutrition from two discrete circulatory systems—the retinal and the choroidal blood vessels. Both are derived from the ophthalmic artery, which is the first branch of the internal carotid artery. The major branches of the ophthalmic artery are the posterior ciliary arteries, the central retinal artery, and the muscular branches. [1] Th

    Dr. Ramesh Venkatesh · Dr. Sajjan Sangai · +1 other
  2. Articles 1 Apr 2021 42 min read

    Optical Coherence Tomography Angiography Made Simple

    Introduction Recent advances in ophthalmic imaging have opened new avenues for a more thorough and extensive understanding of various retinal diseases. Quite a few of these pathologies are attributed directly or indirectly to vascular abnormalities. This renders the need to develop technology capable of providing intricate data of the ocular vasculature. Amongst these is Optical Coherence Tomography Angiography or OCTA. It is a novel, non-invasive imaging modality which provides rapid visualization of the retinal and choroidal microcirculation. Being a dyeless procedure, it eliminates the potential side effects of conventional angiography - i.e Fundus Fluorescein Angiography (FFA)(1) and Indocyanine Green Angiography (ICGA) (2), which require an intravenous injection of a contrast agent. OCTA is a dyeless procedure OCTA derives both functional as well as structural details of the vasculature by detecting the intrinsic motion of the red blood cells within the vessels. (3) By detecting m

    Dr. Nasiq Hasan · Dr. Manasi Tripathi · +1 other
  3. Articles 1 Apr 2021 14 min read

    Ultrasound B-Scan: A Ready Reckoner for the Postgraduates

    The importance of ultrasound imaging cannot be stressed upon more than the fact that whether you are an anterior segment surgeon, posterior segment surgeon or oculoplastic surgeon, the indications for this modality transcend across all genres of ophthalmology. Many a time, postgraduates find this topic daunting to interpret. This article aims to simplify Ultrasound B-scan in terms of mechanics, terminology, actual procedure, and interpretation without delving deep into the confusing jargon. Some common conditions and their typical presentations will also be touched upon. For ease of understanding, we will divide this article into the following sections: History Basic physics and instrumentation Terminology Indications Examination techniques: basic and special Features of commonly encountered posterior segment conditions History Though the concept of ultrasound waves was known to humans in the 18th century (Lazzaro Spallanzini’s observation on the use of ‘sound whistles’ by bats in dark

    Dr. Anmol Naik · Dr. Shveta Gadewar · +1 other
  4. Articles 1 Apr 2021 5 min read

    Ten Tenets of Fundus Autofluorescence

    1. What is fundus autofluorescence? Fundus autofluorescence is a study of the topographic distribution of naturally occurring molecules in the human fundus. These molecules are called fluorophores. In principle, FAF is similar to fundus fluorescein angiography as both of them study the fluorescence pattern of molecules. However, the fluorophore molecules are naturally occurring compounds in the former while in later sodium fluorescein dye is injected. Hence FAF is a non-invasive imaging modality. 2. What are fluorophores? Fluorophores are molecules that emit fluorescence when excited by a suitable wavelength of light. Fluorophores are not exclusively present in the fundus and are distributed in various ocular tissue which includes the cornea, lens, uvea melanocyte, retinal pigment epithelium (RPE), and sclera.1,2 The knowledge about fluorophores other than fundus is still evolving. The commonly studied fundus fluorophores lipofuscin and melanin. 3. Lipofuscin and melanin Lipofuscin is

    Dr. Kumar Saurabh · Dr. Suraj Mistry
  5. Articles 1 Apr 2021 43 min read

    Visual Electrophysiology Made Simple for the Postgraduates

    Visual electrophysiology is an extremely useful tool to study the retinal function objectively. It assesses the functional aspects of not only the retina but also the visual pathway as a whole. Even in this era of advanced imaging, one cannot ignore the importance of the functional aspects of the cellular network in the retina. The commonly used tests with their salient applications are enumerated in Table 1. S.no Test Application 1. Electroretinogram(ERG) Elicits mass response from the Retina 2. Electro-oculogram(EOG) Assesses the function of the Retinal pigment epithelium 3. Pattern ERG(PERG) Differentiates macular and optic nerve pathology 4. Multifocal ERG(MfERG) Picks up focal retinal pathology and maps out the topography 5. Photopic Negative Response(PhNR) Tests the function of retinal ganglion cells 6. Visual Evoked Potentials(VEP) Assesses the visual pathway up to the occipital cortex 7. Multifocal VEP(MfVEP) Picks up focal dysfunction of the visual pathway and maps the topogra

    Dr. Parveen Sen · Karthika Pandurangan · +1 other
  6. Articles 1 Apr 2021 13 min read

    A Beginner's Guide to Ultrasound Biomicroscopy

    Introduction: Anterior segment ocular imaging has gone through various inventions starting from the ultrasound in the 20th century to the recent AS- OCT.1 Ultrasound bio-microscopy, one of the ocular imaging devices is a high-resolution technique, which allows in vivo assessment of the structures of the anterior segment of the eye where cross-sectional images of ocular structures are obtained at microscopic resolution. 2The higher frequency of UBM ranging between 35 and 50 MHz, gives a depth of about 4 mm and an axial and lateral resolution of approximately 25 and 50 microns, respectively. 3 Being a non-invasive technique, efficient regardless of the clarity of the optical media and due to its portability can be performed both in adults and children with no complications.4 The internal acoustic characteristics of UBM, accompanied by the very fine backscatter speckle patterns, permit clear differentiation of ocular tissue at various levels.5 UBM imaging has been very useful in understan

    Dr. Sowkath Ali · Dr. Eunice Goh · +1 other
  7. Articles 1 Apr 2021 30 min read

    Clinical Applications of Multicolor Imaging

    Multicolor imaging (MCI) is a non-invasive retinal imaging modality available in the Spectralis platform (Heidelberg Engineering, Heidelberg, Germany). It simultaneously acquires three reflectance images of the retina using three individual lasers of different wavelengths: blue (488 nm), green (515 nm), and infrared (820 nm). These penetrate the tissue to different depths, simultaneously capturing and depicting information originating from different retinal structures. The infrared reflectance (IR) image visualizes structures at the level of the outer retina and choroid. The green reflectance (GR) image allows imaging of retinal blood vessels, hemorrhages, and exudates. The blue reflectance (BR) particularly provides details of the inner retina and the vitreoretinal interface such as epiretinal membranes, retinal nerve fiber layer (RNFL) thinning, and macular pigment changes. The information from these three images is integrated to form a composite multicolor image.1 Color fundus photo

    Dr. Sugandha Goel · Dr. Rupak Roy

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