Optical coherence tomography OCT is an optical diagnostic technique that allows non-contact, non-invasive tomographic imaging of microscopic structures of living eye tissue. It can observe the anterior segment of the eye and show the morphological structure of the posterior segment of the eye, which has an important role in the diagnosis of retinal diseases, follow-up observation and evaluation of treatment effects. Posterior segment OCT can be used for diagnosis and follow-up of retinal diseases such as glaucoma, macular degeneration, macular anterior membrane, retinal splitting, retinal degeneration, mesoplasm, mesocoria, etc. It is intuitive, fine, convenient and non-invasive, and can also be used for preoperative examination of cataract and excimer surgery to exclude fundus lesions and judge prognosis.