Optic nerve damage There is a structure in the fundus of the human eye called the optic papilla, or optic disc (D), which is like a hole in the wall of the eye. The nerve fibers in the eye converge toward the optic disc to form the optic nerve, which serves to transmit visual signals to the brain. Usually the optic disc is not filled and the remaining space in its center is called the optic cup (C). The ratio of the optic cup to the diameter of the optic disc is called the “cup-to-disc ratio” (C/D). Normally, the cup-to-disc ratio (C/D) should be <0.3. If the IOP continues to rise, it will cause mechanical compression of the optic ganglion cells, resulting in local ischemia and eventually apoptosis of the optic ganglion cells, necrosis of the nerve fiber layer, and an increase in C/D. When your C/D is >0.5, or the difference between the cup-to-disc ratio of both eyes is >0.2, you will be diagnosed with “large optic disc depression”, and your doctor will tell you: “There is a structure in your fundus that is large and suspected to be problematic, and you need to go to the ophthalmology department for further glaucoma screening. “ If you are diagnosed with “large optic disc depression and suspected glaucoma”, you should not be overly nervous, but you should not take it lightly and go to the ophthalmology department for a comprehensive examination. There are two possibilities for “large optic disc depression”, namely, physiological large optic cup and glaucoma, and a clear diagnosis requires close follow-up observation from year to year.