## Methods  
### Instrumentation  
The schematic and photo of our multi-modal anterior eye imager are illustrated in Figure 1. The system combines three optical imaging modules that were installed on two moveable carts (Figure 1b). On the imaging cart, the microvascular imaging module is integrated into the SLB module in a common path optical design with the sample arm of our customized UHR-OCT module adapted on the top (Figure 1c). The reference arm and the spectrometer of the UHR-OCT module are placed on the processing cart together with a computer. Components on the two carts are connected with flexible communication cables and optical fibers to maintain the UHR-OCT stability when adjusting the imaging cart during patient examination. The commercialized SLB module (66 VisionTech, YZ5, Suzhou, Jiangsu, China) has the basic slit-lamp examination function. By turning the control dial and adding/removing the diffuser on the SLB illumination shaper, the SLB illumination light sheet size is adjustable (width: 0-14 mm; length: 1-14 mm) to form the needed thin light sheet or diffused homogeneous illumination. It also offers the function of fluorescein stain imaging by using cobalt blue light of the SLB light source to generate blue excitation light with diffused homogeneous illumination. The microvascular imaging module uses the light source and optical system of the SLB module. Details of the microvascular imaging module development appeared in an earlier publication from our group [31]. In short, as shown in Figure 1a, a digital camera (Canon, EOS 60D, Beijing, China) is built into the SLB optics to acquire conjunctival microvascular network and videography. The camera is attached to the slit-lamp via an inherent camera port of SLB. A green filter (Thorlabs, FGV9, Newton, NJ, USA) is inserted into the illumination path to improve the image quality of the conjunctival vessel network and blood flow videography. The implementation of the camera on the SLB is simple and easy without any modifications or extra adapters. With the built-in optical magnifications of SLB to 25\(\times\) (set by a magnification dial on the SLB) and the 7.5\(\times\) magnification of the digital camera (set by Canon EOS 60D camera Movie Crop Function), the total imaging magnification can reach up to \(\approx\)187.5\(\times\). By imaging a USAF resolution target under the best magnification, as shown in Figure 2a,b, the element 2 of group 7 was readable, corresponding to a lateral resolution of 3.5 \(\upmu\)m, which is sufficient to image the red blood cell (\(\approx\)7 \(\upmu\)m) in the conjunctival microvasculature. The vessel network imaging should be performed under a single-shot mode with the autofocus function of the camera. With a movie crop function that uses a center portion of pixels on the camera chip to perform high-magnification high-speed video recording at 60 frames per second (fps), the movement of red blood cell (RBC) clusters can be recorded for further processing to blood flow velocity. With the digital camera, digital images of the subject appearance and fluorescein stain can also be recorded and displayed on the computer screen in real-time. Our customized UHR-OCT module is a spectral domain OCT system. It uses a broadband superluminescent diode (SLD, Superlum, BLM2-D-840-B-10, Moscow, Russia) that is centered at a wavelength of 840 nm with 100 nm bandwidth. As shown in Figure 1a, after passing an isolator that is used to protect the light source from back reflections, the light from the source is split into the sample arm and the reference arm of the OCT interferometry by a 50:50 fiber coupler. In the sample arm, the OCT light is collimated with a fiber collimator (CL2, Thorlabs, PAF-X-11-B, Newton, NJ, USA), reflected on the galvanometric x-y scanners (G, Cambridge Technology, 6215H set, Bedford, MA, USA), and focused by a lens (L2, f = 100 mm, Edmund Optics, NT45-806, Barrington, NJ, USA) that is installed on a translational stage for focusing adjustment.