## 4 Discussion and Conclusions  
Here, we developed a non-invasive multi-modal imaging platform capable of doing both structural and functional imaging of the anterior eye by combining a customized UHR-OCT module and a microvascular imaging module on a traditional slit-lamp microscopy system for the first time. An axial resolution of \(\approx 2.9\)\(\upmu\)m in corneal tissue was achieved by the UHR-OCT module for high-resolution corneal structure imaging. The microvascular imaging module had a lateral resolution of 3.5 \(\upmu\)m with magnification up to \(\approx 187.5\times\), resolving the conjunctival microvasculature and the moving clusters of red blood cells. With the multi-modal anterior eye imager, a high-resolution cross-sectional OCT image, a conjunctival vessel network image, conjunctival blood flow videography, a fluorescein staining image and a normal SLB image of in vivo human anterior eye could be achieved within 20 min by a well-trained examiner--much more efficient than the current examination scheme by different imaging modalities in ophthalmic clinics. We have successfully demonstrated the system's feasibility by providing multi-modal information to show its potential for ophthalmic clinical application by imaging a healthy subject and a keratitis patient. With customized software, quantitative morphological and homodynamic vessel parameters were further obtained. Preliminary differences in the vessel density, complexity, vessel diameter and blood flow rate between the healthy subject and the keratitis patient were recognized which were consistent with clinical manifestations of vessel dilation, distortion and increased blood flow after inflammation [5; 6]. Based on our literature searching, though various multi-modal ophthalmic imaging systems have been demonstrated for human eye imaging, only a few have been developed for the anterior segment. The integration of OCT with SLB conducted by both [PERSON] et al. [41] and [PERSON] et al. [42] can image both anterior and posterior segments more efficiently but only provides structural images. Other groups have applied the combinations of OCT [43; 44] or a Scheimpflug camera [45] and corneal topography with a focus only on the anterior segment biometry measurements. Compared with current ophthalmic imaging modalities, our self-developed multi-modal anterior eye imager not only offers precise structural information with the UHR-OCT module, but also provides functional information of bulbar conjunctival vessels through the microvascular imaging module. With the multi-modal and multi-dimensional information, our system would potentially help ophthalmologists to achieve more comprehensive evaluations, and more accurate diagnoses and quantitative classifications of anterior eye diseases. Future work on system improvement will be focused on increasing the UHR-OCT imaging speed to achieve three-dimensional imaging in real-time. As the morphological and hemodynamic parameters of the bulbar conjunctival vessels could potentially be used to access the status of ocular surface diseases, large scale clinical studies will need to be conducted to comprehensively characterize the relations between these quantitative parameters of human bulbar conjunctival microvasculature \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Mono-fractal** & **Multi-fractal** & **Mean** & **Cross-sectional** & **Axial Velocity** & **Cross-sectional** & **Flow Rate** \\  & **D\({}_{\text{box}}\)** & **D\({}_{\text{0}}\)** & **D\({}_{\text{0}}\)** & **A(um-)** & **V\({}_{\text{4}}\) (mm/s)** & **V\({}_{\text{s}}\) (mm/s)** & **Q(p/s)** \\ \hline Healthy Subject & 1.51 & 1.52 & 17.84 \(\pm\) 1.52 & 251.40 \(\pm\) 44.43 & 0.26 \(\pm\) 0.07 & 0.18 \(\pm\) 0.05 & 61.82 \(\pm\) 22.29 \\ Keratitis patient & 1.59 & 1.76 & 23.12 \(\pm\) 1.00 & 419.68 \(\pm\) 37.00 & 0.27 \(\pm\) 0.06 & 0.18 \(\pm\) 0.06 & 119.3 \(\pm\) 42.17 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the quantitative vessel parameters of the healthy and keratitis patient.