## 2 Materials and Methods  
This cross-sectional study enrolled patients diagnosed with CO who were referred to the Eye and ENT Hospital of Fudan University, China, from September 2021 to January 2022. The study was approved by the Institutional Review Board of the Eye and ENT Hospital of Fudan University (protocol code: 2021014, date of approval: 4 February 2021). All procedures were conducted in accordance with the principles of the Declaration of Helsinki. Subjects with poor visual acuity due to severe media opacity and inability to fixate for OCTA image acquirement were excluded from the study. For each patient, a detailed medical record was compiled, and a complete ophthalmologic examination performed at the baseline visit. Demographic data included age, gender, laterality, best-corrected visual acuity (BCVA), and history of intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections. Multimodal imaging included color fundus photography (Topcon TRC50 LX; Topcon, Tokyo, Japan), B-scan ultrasonography or computerized tomography, and simultaneous FA and ICGA by Spectralis HRA + OCT (Heidelberg Engineering, Heidelberg, Germany). Tumor characteristics included location (macula, juxtapapillary, or circumpapillary), greatest linear dimension on ultrasonography, presence of CNV and focal choroidal excavation (FCE), whether hyperreflective tumor-like tissue was growing over Bruch's membrane, and number of tumors (single or multi-focal). All patients underwent SS-OCT and SS-OCTA (TowardPi BMizar, TowardPi Medical Technology, Beijing, China) after pupil dilation to obtain amplitude-decorrelation angiography images. For SS-OCT, we captured radiation and raster scans of each osteoma lesion. A vertical-cavity surface-emitting laser was used to sweep sources with an A-scan rate of 400 KHz (BMizar) and wavelength centered at 1060 nm. The bandwidth of 100 nm enabled an axial optical resolution of 3.8 \(\upmu\)m; the transverse resolution was 10 \(\upmu\)m. The high coherence range provided homogeneous signal strength over a depth range of 6 mm for the vitreous, retina, choroid, and sclera. The eye tracking rate of 128 Hz eliminated interference from eye motion and blinks. The special lens of TowardPi OCT system does not like additional-lens-using for imaging the anterior segment; it is an optical design within a complete set of the system. With a group of large-diameter lenses (ocular lenses more than 60 mm across), the field of view (FOV) of the system reaches up to 120\({}^{\circ}\), while maintaining a lateral resolution of 10 \(\upmu\)m. The B-scan length can be adjusted from 3 to 24 mm, according to the tumor size. A 24 mm B-scan consists of 1536 A-scans, with 2560 samples along each A-scan. Each scan position can be repeated up to 256 times to obtain an average image with high SNR. For SS-OCTA, the choice of 24 \(\times\) 20 mm, \(18\times 18\) mm, or 12 \(\times\) 12 mm scanning protocols enables a large view of the osteoma lesion according to the tumor size, enabling high-resolution images of CNV and feeder vessels. Unlike 2D images from color photographs or FA, OCTA images consist of three-dimensional data points. The collection of width, height, and depth data leads to a marked increase in data volume. A single 24 \(\times\) 20 mm OCTA image consists of 1280 line positions, 1536 A-scans of each line, and 2560 points on each A-scan, with the scanning repeated at least twice. The interval of A- and B-scans is 15.625 \(\upmu\)m, similar to most HD OCTA images at small sizes. As a result, a TowardPi OCTA image with a width of 24 mm comprises over ten billion voxels. In addition, a 400 KHz swept source is insufficient to bring a 120\({}^{\circ}\) OCTA imaging modality into real practice. Amongst the supporting hardware, the DAQ is one of the key components. The DAQ needs to have rapid operation to overmatch the 400 KHz rate, with a high S/N ratio, which is extremely costly in the industrial market and is therefore not ideal for a commercial ophthalmic imaging device.