الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 86 |  |  |
| | | from | 86 | | |
Abstract
Optical Coherence Tomography Angiography (OCTA) is an easy, fast, noninvasive imaging modality which employs motion contrast imaging to high-resolution volumetric blood flow information. Unlike FA and ICG angiography which are two dimensional images, OCTA is basically a cube scan with a three-dimensional (3D) assessment of the retinal vessels. It compares the decorrelation signal between consecutive OCT b-scans taken at the same cross-section in order to build up a map of blood flow. It eliminates the axial-bulk motion resulting from patient movement. So, the sites of motion between repeated OCT b-scans are strictly due to the movement of RBCs in retinal vasculatures.
In OCT angiogram, each retinal layer can be separately viewed. The software uses a perfusion density analysis to translate each layer of the OCT angiogram into qualitative and quantitative data. OCT angiograms are produced by using a gray scale.
For each microvascular layer, the capillary perfusion density (CPD) was measured. The vascular density information from more superficial vascular layers was subtracted to quantify the perfusion density for the deeper layers allowing for precise analysis of each layer separately. for each subject the perfusion density analysis was done for all 3 layers in both the 3×3-mm and6×6-mm scans.
In the current study we used Carl Zeiss (6000) Meditec Angioplex. Which based on SD- OCT systems. It has a scanning speed of 100,000 A-scans per second. It provides a wider field of view up to 12mm in a single scan. It captures high-definition (HD) OCT and OCTA scans, revealing detailed retinal microvascular and providing more information about patient’s condition.
The aim of this work is to collect normative data about the macular perfusion, vascular density and FAZ area in superficial retinal capillary plexus in normal Egyptian volunteers using OCTA. According to the ETDRS, the macula was segmented into three concentric circles with diameters of 1 mm, 3 mm, and 6 mm. The pericentral and peripheral rings were equally divided into four regions: superior, nasal, inferior, and temporal.
The software acquires perfusion indices for each en‑face zones, in parafoveal (central, 3 mm) and perifoveal (between 3‑6 mm) areas. Central foveal avascular zone is automatically excluded from measurements of the perfusion indices. The FAZ area (mm2) can be measured in the central area using the in‑built software.
This prospective study was conducted on 80 eyes of normal subjects. 38 eyes were of males and 42 eyes were of females. Only one eye of each individual was included. Their age ranged from 19.01 to 49.04 with a mean of 31.45 ± 8.91. They were divided into 3 age groups for better data representation. The ages of the first group were less than 30 years, the second group ages ranged from 30 to 40 years, while the third group ages were more than 40 years old.