  Color fundus photography and Optical Coherence Tomography (OCT) are the two
most cost-effective tools for glaucoma screening. Both two modalities of images
have prominent biomarkers to indicate glaucoma suspected. Clinically, it is
often recommended to take both of the screenings for a more accurate and
reliable diagnosis. However, although numerous algorithms are proposed based on
fundus images or OCT volumes in computer-aided diagnosis, there are still few
methods leveraging both of the modalities for the glaucoma assessment. Inspired
by the success of Retinal Fundus Glaucoma Challenge (REFUGE) we held
previously, we set up the Glaucoma grAding from Multi-Modality imAges (GAMMA)
Challenge to encourage the development of fundus \& OCT-based glaucoma grading.
The primary task of the challenge is to grade glaucoma from both the 2D fundus
images and 3D OCT scanning volumes. As part of GAMMA, we have publicly released
a glaucoma annotated dataset with both 2D fundus color photography and 3D OCT
volumes, which is the first multi-modality dataset for glaucoma grading. In
addition, an evaluation framework is also established to evaluate the
performance of the submitted methods. During the challenge, 1272 results were
submitted, and finally, top-10 teams were selected to the final stage. We
analysis their results and summarize their methods in the paper. Since all
these teams submitted their source code in the challenge, a detailed ablation
study is also conducted to verify the effectiveness of the particular modules
proposed. We find many of the proposed techniques are practical for the
clinical diagnosis of glaucoma. As the first in-depth study of fundus \& OCT
multi-modality glaucoma grading, we believe the GAMMA Challenge will be an
essential starting point for future research.
