**Clinical Retina**

**Chapter 1**

**Provisional chapter**

**Novel Insight into Morphological Features and**

**Novel Insight into Morphological Features and** 

**Optical Coherence Tomography Angiography**

**Optical Coherence Tomography Angiography**

Magdy Moussa and Mahmoud Leila

Magdy Moussa and Mahmoud Leila

http://dx.doi.org/10.5772/intechopen.78679

SS-OCT angiography (SS-OCTA).

disease, OCTARA algorithm, swept-source OCT

**Abstract**

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

**Vascular Profile of Selected Macular Dystrophies Using**

**Vascular Profile of Selected Macular Dystrophies Using** 

Our perception of macular dystrophies has evolved overtime from collective grouping into hereditary disorders of unclear etiology and no effective treatment to avid search for the underlying pathogenic mechanism that would provide base for future therapy. A causal conjunction between abnormalities in the photoreceptors layer and the RPE— Bruch's membrane complex and abnormal profile of the retinal vascular plexuses and the choriocapillaris—stands out as a plausible theory of pathogenesis. The recently introduced swept-source optical coherence tomography (SS-OCT) technology incorporates long-wavelength (1050-nm) scanning light, less susceptibility to sensitivity roll-off, and ultrahigh-speed image acquisition. These features enabled in vivo noninvasive visualization of different strata of the outer retina and the choriocapillaris with unprecedented finesse. Furthermore, the SS-OCT technology incorporated a blood flow detection algorithm; OCTARA that in tandem with the deeper penetration and superior axial resolution of SS-OCT enabled detailed assessment of the retinal capillary plexuses and the choriocapillaris in terms of structure and density. This novel technology could help explore yet undiscovered frontiers in the pathophysiology of macular dystrophies and guide future therapeutic approaches. This chapter includes a review of literature along with the authors' experience in imaging selected macular dystrophies using SS-OCT and

**Keywords:** imaging macular dystrophies, SS-OCTA in Stargardt's, SS-OCTA in Best's

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.78679

**Swept-Source Optical Coherence Tomography and**

**Swept-Source Optical Coherence Tomography and** 

#### **Novel Insight into Morphological Features and Vascular Profile of Selected Macular Dystrophies Using Swept-Source Optical Coherence Tomography and Optical Coherence Tomography Angiography Novel Insight into Morphological Features and Vascular Profile of Selected Macular Dystrophies Using Swept-Source Optical Coherence Tomography and Optical Coherence Tomography Angiography**

DOI: 10.5772/intechopen.78679

Magdy Moussa and Mahmoud Leila Magdy Moussa and Mahmoud Leila

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78679

#### **Abstract**

Our perception of macular dystrophies has evolved overtime from collective grouping into hereditary disorders of unclear etiology and no effective treatment to avid search for the underlying pathogenic mechanism that would provide base for future therapy. A causal conjunction between abnormalities in the photoreceptors layer and the RPE— Bruch's membrane complex and abnormal profile of the retinal vascular plexuses and the choriocapillaris—stands out as a plausible theory of pathogenesis. The recently introduced swept-source optical coherence tomography (SS-OCT) technology incorporates long-wavelength (1050-nm) scanning light, less susceptibility to sensitivity roll-off, and ultrahigh-speed image acquisition. These features enabled in vivo noninvasive visualization of different strata of the outer retina and the choriocapillaris with unprecedented finesse. Furthermore, the SS-OCT technology incorporated a blood flow detection algorithm; OCTARA that in tandem with the deeper penetration and superior axial resolution of SS-OCT enabled detailed assessment of the retinal capillary plexuses and the choriocapillaris in terms of structure and density. This novel technology could help explore yet undiscovered frontiers in the pathophysiology of macular dystrophies and guide future therapeutic approaches. This chapter includes a review of literature along with the authors' experience in imaging selected macular dystrophies using SS-OCT and SS-OCT angiography (SS-OCTA).

**Keywords:** imaging macular dystrophies, SS-OCTA in Stargardt's, SS-OCTA in Best's disease, OCTARA algorithm, swept-source OCT

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **1. Introduction**

Macular dystrophy is a unifying term used to describe a group of hereditary fundus disorders that exhibits Mendelian inheritance pattern and has varying degrees of expressivity and penetrance. These disorders share common criteria in that they are isolated, that is, confined to the eye with no systemic association, limited to the anatomic macula, exhibit bilateral involvement with striking symmetry, and have characteristic biomicroscopic features that manifest universally along with visual symptoms or often discovered on routine examination before symptoms develop. The classic tools for the diagnosis and follow-up of macular dystrophies were largely based on clinical appearance, electrophysiologic findings, and fundus fluorescein angiography (FFA). More recently, fundus autofluorescence (FAF) increasingly became an invaluable noninvasive tool in the follow-up scheme of these patients [1–7]. FAF captures the stimulated emission of light from lipofuscin molecules that accumulate excessively in cases of retinal pigment epithelium (RPE) dysfunction and depicts specific autofluorescence patterns that are characteristic for each disease [8–11]. To date, there is no known effective treatment for macular dystrophies other than the management of complications, for example, choroidal neovascularization (CNV) secondary to Best's disease and visual rehabilitation using low-vision aids [1, 2].

**3. Optical coherence tomography angiography (OCTA): a new** 

avoid biased results and reduce the economic burden on health-care institutions.

**4. Swept-source optical coherence tomography (SS-OCT), SS-OCT** 

SS-OCTA incorporates a blood flow detection algorithm; OCTARA (Optical Coherence Tomography Angiography Ratio Analysis); Topcon Corporation, Tokyo, Japan. OCTARA uses decorrelation motion contrast between rapidly repeated SS-OCT B-scans to detect moving erythrocytes in relation to static tissue [20]. SS-OCTA is integrated in the SS-OCT technology which incorporates a long-wavelength (1050-nm) scanning light, reduced sensitivity roll-off feature, and ultrahigh-speed image acquisition. These implements enable deeper penetration with minimal light scattering, hence superior axial resolution and segmentation of different retinal layers. The result is the generation of ultrahigh-definition images of the retinal microstructure, retinal vascular plexuses, and the choriocapillaris, while obviating the need for dye injection. It is worth noting that OCTARA algorithm generates SS-OCTA images by registering B-scan repetition at each scan location, thereby computing a ratio-based result between corresponding image pixels. This method preserves the integrity of the OCT spectrum and does not result in compromised axial resolution, an inherent disadvantage of other OCTA technologies [20–25]. In addition, SS-OCTA software generates color-coded flow density maps of the retinal vascular plexuses and the choriocapillaris, each layer separately.

**angiography (SS-OCTA), and OCTARA algorithm**

The prospect of an abnormal vascular profile going on in tandem with the morphological changes in retinal microstructure in macular dystrophies turned our attention to the diagnostic and therapeutic potentials of the early detection of abnormal changes in the retinal vascular plexuses and the choriocapillaris. Currently, the available diagnostic modalities rely on inference extrapolated from indirect evidence to determine disease stage and progression. For instance, FFA depicts disease patterns based on varying degrees of fluorescence; FAF identifies diseased or dead RPE cells based on varying intensities of lipofuscin autofluorescence, whereas electrophysiology records the amplitude and latency of electric transduction in retinal layers to identify different dystrophies [1–3, 8–11]. The common factor among these diagnostic tools is that they reveal useful information only when retinal function due to a given dystrophy has already been compromised. In comparison, OCTA offers direct noninvasive visualization of the vascular profile in macular dystrophies and thus has the clear advantages of screening vulnerable population and detecting the disease process in its nascence. Though no therapeutic line is currently available for macular dystrophies, the identification of early disease phases based on the integrity of the vascular profile helps selecting patients who would be best candidates for on-going research trials on gene therapy and pluripotent stem cell transplantation. On the other hand, identifying patients with severely compromised vascular profile, and in whom favorable outcome of these therapies is unlikely, will help

Novel Insight into Morphological Features and Vascular Profile of Selected Macular Dystrophies…

http://dx.doi.org/10.5772/intechopen.78679

5

**imaging frontier**
