## 2 Retinal Vascular Diseases
### Diabetic Retinopathy (DR)
#### 2.1.1 Detection of DR
The value of various metrics to gauge the shape of the FAZ has also been called into question, as the clinical utility of varying distortions of \"normal\" shape have unclear clinical implications at the moment. Vessel Density at the Macula  
While macular vessel density is decreased in diabetics [45], there are conflicting data as to whether it is more reduced in the SCP than the DCP, vice versa or to approximately the same extent [46]. OCTA studies revealed a reduction of macular VD in diabetic patients with DR with positive correlation to the severity of DR [45]. Figure 2 shows reduction of VD in both DCP and SCP in a diabetic patient compared to control. [PERSON] et al. [47] showed significantly lower VD in subjects of diabetes with DR when compared to healthy control eyes in both SCP and DCP. [PERSON] et al. [36] found that VD was reduced significantly in the SCP and DCP in diabetic subjects with DR with normal VA in comparison with healthy controls. This reduction is even more in patients of diabetes with DR and decreased VA (without macular edema). They concluded that the reduction in vessel density in patients with diabetes with DR is positively correlated with decreased \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Study** & **No. of Patients** & **Age** & **SCP-FAZ** & **SCP-FAZ** & **DCP-FAZ** & **DCP-FAZ** \\  & **Patients** & & **(Control) (mm\({}^{2}\))** & **(DR) (mm\({}^{2}\))** & **(Control) (mm\({}^{2}\))** & **(DR) (mm\({}^{2}\))** \\ \hline [PERSON] et al. [34] & 20 & 65.8 \(\pm\) 8.7 & 0.25 \(\pm\) 0.06 & 0.38 \(\pm\) 0.11 & 0.38 \(\pm\) 0.11 & 0.56 \(\pm\) 0.12 \\ [PERSON] et al. [20] & 11 & 55.7 \(\pm\) 10 & 0.3 \(\pm\) 0.11 & 0.49 \(\pm\) 0.19 & & \\ [PERSON] et al. [35] & 13 & 66.5 \(\pm\) 10.4 & 0.31 \(\pm\) 0.09 & 0.36 \(\pm\) 0.13 & 0.45 \(\pm\) 0.17 & 0.71 \(\pm\) 0.2 \\ [PERSON] et al. [36] & 22 & 30 \(\pm\) 6 & 0.20 \(\pm\) 0.07 & 0.3 \(\pm\) 0.11 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average areas of FAZ in both normal and DR cases. [PERSON] et al. [48] reported a significant reduction in the density of the vessels in the SCP in patients with diabetes with early DR when compared to healthy controls. However, no significant difference was found in retinal thickness between diabetic subjects and healthy controls. They concluded that compromised microvascular circulation precedes retinal structural changes. Table 2 lists the average VD in both normal and DR cases. Microaneurysms  
Microaneurysms were identified on OCTA as a well-demarcated saccular or fusiform shapes of focally dilated capillaries in the SCP and DCP but mainly in the deep plexus [49]. [PERSON] et al. [50] compared the detection of microaneurysms in diabetic retinopathy using FA and OCTA. They found that only 23% of microaneurysms detected on FA were identified on OCTA. They also found variation in both shape and size of microaneurysms \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline \multirow{2}{*}{**Study**} & **No. of Patients** & \multirow{2}{*}{**Age**} & **SCP-VD** & **SCP-VD** & **DCP-VD** & **DCP-VD** \\  & **Patients** & & **(Control) (mm2)** & **(DR) (mm2)** & **(Control) (mm2)** & **(DR) (mm2)** \\ \hline [PERSON] et al. [47] & 13 & \(56.66\pm 12.65\) & \(55.6\pm 1.7\) & \(48.2\pm 4.6\) & \(60.6\pm 1.5\) & \(53.6\pm 3.2\) \\ [PERSON] et al. [36] & 22 & \(30\pm 6\) & \(49.1\pm 2.5\) & \(44.1\pm 2.5\) & \(50.6\pm 3.3\) & \(44.3\pm 3.2\) \\ [PERSON] et al. [48] & 49 & \(56.4\pm 10.1\) & \(54.1\pm 2.1\) & \(47.82\pm 4.62\) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The average VD in both normal and DR cases. Figure 2: Vessels density. (**a**) SCP of normal control, (**b**) DCP of normal control, (**c**) SCP of the a diabetic patient, and (**d**) DCP of a diabetic patient. detected by the two techniques. Microaneurysm appeared on FA as uniform round dots, while they appeared on OCTA smaller in size with multiple different shapes such as fusiform, solid round or round with dark centers. [PERSON] et al.