## 2 Retinal Vascular Diseases
### Age-Related Macular Degeneration (AMD)  
AMD is a primary cause of blindness of adults above 50 years old in developed countries [73]. Neovascular AMD represents nearly 10% of AMD cases [74]. The onset of neovascular AMD determines the progress of the development of AMD from intermediate non-exudative to late exudative. Neovascular AMD refers to the abnormal growth of new vessels either underneath the RPE (neovascularization type 1), between the retina and the \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline \multirow{2}{*}{**Study**} & \multirow{2}{*}{\begin{tabular}{c} **No. of** \\ **Patients** \\ \end{tabular} } & \multirow{2}{*}{**Age**} & \begin{tabular}{c} **SCP-VD** \\ **(Control) (mm2)** \\ \end{tabular} & \begin{tabular}{c} **SCP-VD** \\ **(DR) (mm2)** \\ \end{tabular} & \
\begin{tabular}{c} **DCP-VD** \\ **(Control) (mm2)** \\ \end{tabular} &
\begin{tabular}{c} **DCP-VD** \\ **(DR) (mm2)** \\ \end{tabular} \\ \hline [PERSON] et al. [46] & 25 & \(22\pm 2\) & & & & \\ [PERSON] et al. [31] & 28 & \(42.3\pm 8.6\) & & & & \\ [PERSON] et al. [68] & 20 & \(38.5\pm 12.4\) & \(51.5\pm 4.2\) & \(58.7\pm 3.6\) & & \\ [PERSON] et al. [66] & 29 & \(69\pm 9.01\) & \(51.39\pm 13.05\) & \(44.35\pm 13.31\) & \(41.53\pm 14.08\) & \(31.03\pm 16.33\) \\ [PERSON] et al. [64] & 71 & \(57.4\pm 13.5\) & \(55.72\pm 2.43\) & \(51.34\pm 4.09\) & \(62.10\pm 2.11\) & \(57.66\pm 5.73\) \\ [PERSON] et al. [70] & 66 & \(58.77\pm 12.3\) & \(50.42\pm 3.73\) & \(48.12\pm 4.01\) & \(52.71\pm 6.56\) & \(48.62\pm 6.39\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The average VD in both normal and early DR cases. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline \multirow{2}{*}{**Study**} & \multirow{2}{*}{\begin{tabular}{c} **No. of** \\ **Patients** \\ \end{tabular} } & \multirow{2}{*}{**Age**} & \begin{tabular}{c} **SCP-FAZ** \\ **(Control) (mm2)** \\ \end{tabular} & \begin{tabular}{c} **SCP-FAZ** \\ **(DR) (mm2)** \\ \end{tabular} & \
\begin{tabular}{c} **DCP-FAZ** \\ **(Control) (mm2)** \\ \end{tabular} &
\begin{tabular}{c} **DCP-FAZ** \\ **(DR) (mm2)** \\ \end{tabular} \\ \[PERSON] et al. [65] & 39 & \(60\pm 20.55\) & \(0.28\pm 0.13\) & \(0.34\pm 0.10\) & & \\ [PERSON] et al. [34] & 24 & \(62.9\pm 9.8\) & \(0.25\pm 0.06\) & \(0.37\pm 0.07\) & \(0.38\pm 0.11\) & \(0.54\pm 0.13\) \\ [PERSON] et al. [20] & 11 & \(55.7\pm 10\) & \(0.3\pm 0.11\) & \(0.41\pm 0.19\) & & \\ [PERSON] et al. [35] & 14 & \(66.5\pm 10.4\) & \(0.31\pm 0.09\) & \(0.36\pm 0.13\) & \(0.45\pm 0.17\) & \(0.70\pm 0.2\) \\ [PERSON] et al. [66] & 23 & \(69\pm 9.01\) & \(0.31\pm 0.10\) & \(0.37\pm 0.11\) & & \\ [PERSON] et al. [67] & 60 & \(57.4\pm 15.4\) & \(0.28\pm 0.13\) & \(0.35\pm 0.12\) & \(0.36\pm 0.14\) & \(0.49\pm 0.15\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Average areas of FAZ in normal and early DR cases. RPE (neovascularization type 2), or starting within the retina (neovascularization type 3). Types 1 and 2 neovascularization are known as choroidal neovascularization (CNV) as they are derived from the choroidal circulation [75]. However, type 3 neovascularization refers to the retinal angiomatous proliferation as it arises initially from retinal circulation [76]. CNV onset in AMD was determined by macular exudation onset, which is recognized by either the leakage during FA [77], the existence of macular fluid in OCT [78], or the existence of vascular flow abnormal pattern in OCTA [79]. The most popular category of exudative AMD is type 1 CNV [76]. OCTA is also used in imaging the neovascular membrane inside the macula non-invasively. Even if there is no exudation, in OCTA, CNV type 1 is shown as vessels network located between the Bruch's membrane and the retinal pigment epithelium (RPE) [80], whereas CNV type 2 is visualized as vessels network in the normally avascular outer retina [81]. Furthermore, type 3 neovascularization is visualized as a discrete high flow linear structure that extends from middle layers in the retina into the deep retina and occasionally also past the RPE [82].