## Methods
### Instrumentation
To integrate the UHR-OCT sample arm to the SLB module, a 45-degree hot mirror (HM, Edmund Optics, NT64-471, Barrington, NJ, USA) is installed in front of the SLB imaging port and reflects the focused OCT beam to the human eye. The power of incident light on the human eye is adjusted to 750\(\upmu\)W, below the maximum permissible exposure dictated by ANSI (American National Standard for Ophthalmics--Light Hazard Protection for Ophthalmic Instruments) [46]. The light going to the reference arm is collimated by  
Figure 1: Schematic and photo of the multi-modal anterior eye imager. (**a**) Schematic of the system, SLD: superluminescent diode, CL: collimator, NF: neutral-density filter, L: lens, G: galvano, TS: translational stage, DG: diffraction grating, LSC: line scanning camera, HM: hot mirror, IS: illumination shaper, BS: beam splitter, MD: magnification dial, OL: ocular lens. The UHR-OCT beam is depicted in red; the microvascular imaging module and SLB beam are depicted in green. Black dashed line-framed parts are installed on the processing cart, while blue dashed line-framed parts are installed on the imaging cart. (**b**) Photo of the system and (**c**) the side-view of the zoom-in area. a fiber collimator (CL1, Thorlabs, PAF-X-7-B, Newton, NJ, USA), passed through a neutral-density filter (NF, Thorlabs, NDC-25C-4M, Newton, NJ, USA) for reference signal control and focused on a mirror by a focusing lens (L1, f = 100 mm, Edmund optics, NT45-806, Barrington, NJ, USA). The optical pathlength of the reference arm is matched with the sample arm to the focal position. The light reflected from the eye in the sample arm and the mirror in the reference arm are collected, combined and sent to the self-built OCT spectrometer. The spectrometer is composed of a collimating lens (CL3, f = 50 mm, OZ Optics, HPUCO-23 AF-830-S-50 AC, Ottawa, Canada), a 1200 lines/mm volume holography transmission grating, an image enlargement lens (L3, f = 180 mm, Schneider, PROJ.3.5/180, Bad Kreuznach, Germany) and a line array CCD camera (LSC, E2V, Aviiva SM2, San Jose, CA, USA). The spectrum of the interference signal is acquired with a maximum speed of 24,000 A-lines per second, transferred using the image acquisition board (National Instruments, PCIe-1428, Austin, TX, USA) and processed by our self-developed LabVIEW program running on a computer with Windows 10. Figure 2c shows the measured spectrum of the light source in our system. By imaging a mirror, the axial resolution of our UHR-OCT module was measured to be \(\approx\)4\(\upmu\)m in the air (Figure 2d), corresponding to \(\approx\)2.9 \(\upmu\)m in corneal tissue with a refractive index of 1.38 [47]. The scanning range is adjustable up to 12 mm on the ocular surface of the human subject. A head-rest is installed on the imaging cart table for its forehead and chin rests for the subjects during imaging, to minimize head movements. A fixation light is used as an external fixation target to guide the non-examined eye of the subject, thereby reducing eye movements during image acquisition and changing the imaging position for OCT and microvascular imaging. The entire optical parts on  
Figure 2: System performance characterization. (**a**) Representative image of the microvascular imaging module imaging a USAF resolution target with the highest magnification of 187.5x. (**b**) Zoom-in area of the red box area in (**a**), showing that element 2 of group 7 was readable, corresponding to a lateral resolution of 3.5 \(\upmu\)m. (**c**) Measured light source spectrum of the UHR-OCT system. (**d**) Measured axial point spread function (PSF) of the UHR-OCT system by imaging a mirror in air. the imaging cart can be adjusted in three dimensions with the slide way of the SLB module and the table lift for imaging convenience.