# Fractal Dimension and Retinal Pathology: A Meta-Analysis
## 3 Results
### Results of Meta-Analysis  
The results of the meta-analysis are reported in Table 4. Meta-analysis was conducted for the disease categories: diabetic retinopathy, diabetes mellitus, myopia, hypertension, and glaucoma. Studies examining retinal occlusions, AMD, NIAION, and MacTel2 were excluded due to those categories each having less than two studies found from the search. Due to some studies stratifying their results by disease severity and/or retinal vascular layer, the averaged result was taken for those cases. For example, [PERSON] et al. (2016) provides mean (SD) FD values for both the deep and superficial capillary plexuses of the control group but not for the whole retina [40]; to obtain a value suitable for use in the meta-analysis, the combined mean and SD was computed with the two samples. Study effect sizes were calculated by subtracting the normal group mean from the case group mean. Due to heterogeneity between studies, a random effect model [21] was used to \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Author (Year)** & **RVPs** & **Imaging Device** & **FD ROI** & **FD Calculation** & **Results** \\ \hline \multirow{8}{*}{[PERSON] et al. (2013)} & \multirow{8}{*}{BAa/v, TORTa/v, FDt} & 45\({}^{\circ}\) digital retinal & & & Eyes with glaucoma had significantly lower \\  & & camera (Canon & Circular region of & FD. Similarly, eyes \\  & & CR-DGi with a 10D & 0.5–2.0 disc & Box-counting & with ocular \\  & FDt & SLR digital camera & diameters from the & using SIVA & hypertension had \\  & & backing; Canon, & disc margin. & & significantly lower \\  & & Tokyo, Japan) & & & FD. FD was also \\  & & & & lower in eyes with \\  & & & & higher IOP. \\ \hline \multirow{8}{*}{[PERSON] et al. (2020)} & Vessel density, & & & & FD of the SRL and \\  & skeleton density, & & Whole area & DRL showed \\  & vessel diameter & & XR Avanti; & permitted by & Box-counting & significant \\  & index, FD, FAZ & & Optovue Inc., & 6 \(\times\) 6 mm scan & method with & reduction when \\  & & caliber (calculated & & centered on & Fractalvese & comparing \\  & for both superficial & & the fovea. & & hypertensive eyes \\  & and deep & & & with controls. \\  & retinal layers) & & & & \\ \hline \multirow{8}{*}{[PERSON] et al. (2016)} & \multirow{8}{*}{FDt, FD\_SVP, FD\_DVP. All repeated with separation of large from micro vessels} & \multirow{8}{*}{Optovue RTVue XR Avanti; & & & \\  & & & Anterior temporal, & & \\  & & & Anterior temporal, & & \\  & & & Superior nasal, and & & \\  & & & inferior nasal. The & & \\  & & & annular zone was & & \\  & & & & annular zone was & \\  & & & & also divided into 6 & \\  & & & thin annuli with & & \\  & & & width –0.16 mm & & \\  & & & denoted C1-C6. & & \\ \hline \multirow{8}{*}{[PERSON] et al. (2016)} & \multirow{8}{*}{FD\_SCP, FD\_DCP, CVSel density} & \multirow{8}{*}{Optovue RTVue XR Avanti; & Whole area & & The average FD for diabetic eyes was \\  & & & XR Avanti; & permitted by & Box-counting & significantly lower \\  & & & 3 \(\times\) 3 mm scan & method with & than control eyes \\  & vessel density & & Octovue Inc., & centered on & Fractalvese & for the superficial \\  & & & the fovea. & & and deep \\  & & & & capillary plexuses. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._synthesize all study effect sizes to derive a summary effect size and its 95% confidence interval for each disease category. The diabetic retinopathy and myopia categories had the most data available and had summary effect sizes [95% C.I.] of \(-\)0.00269 [\(-\)0.0441, \(-\)0.0097] and \(-\)0.0176 [\(-\)0.0279, \(-\)0.0073] respectively, suggesting decreased fractal dimension for those pathologies. The other categories: diabetes mellitus, hypertension, and glaucoma had summary effect sizes [95% C.I.] of \(-\)0.0118 [\(-\)0.0453, 0.0218], \(-\)0.0054 [\(-\)0.0125, 0.0017], and \(-\)0.0049 [\(-\)0.0423, 0.0324] respectively with the relationship remaining uncertain due the confidence intervals encompassing positive effect sizes as well.