Table 2. Summary of OCT based angiography algorithms.

Algorithm	Contrast formula
Power intensity differential (PID) [12]*	$f_{PID}(z)={\displaystyle \sum _{t=1}^{M-1}{\left[I(z,t+1)-I(z,t)\right]}^2}$ where $I(z,t)=20{\log }_{10}R(z,t)$
Intensity-based Doppler variance [17]*	$f_{IBDV}(z)=1-\frac{{\displaystyle \sum _{t=1}^{M-1}{\displaystyle \sum _{k=-L}^{L}w(k)\left|R(z-k,t)\right|\left|R(z-k,t+1)\right|}}}{{\displaystyle \sum _{t=1}^{M-1}{\displaystyle \sum _{k=-L}^{L}w(k)\frac{1}{2}\left[{\left|R(z-k,t)\right|}^2+{\left|R(z-k,t+1)\right|}^2\right]}}}$
Complex differential variance	$f_{CDV}(z)=\sqrt{1-\frac{{\displaystyle \sum _{t=1}^{M-1}\left|{\displaystyle \sum _{k=-L}^{L}w(k)R(z-k,t)R^{*}(z-k,t+1)}\right|}}{{\displaystyle \sum _{t=1}^{M-1}{\displaystyle \sum _{k=-L}^{L}w(k)\frac{1}{2}\left[{\left|R(z-k,t)\right|}^2+{\left|R(z-k,t+1)\right|}^2\right]}}}}$

    * The contrast formulae are presented in their original form without square-root transformation