In clinical work, we often come across patients who find that their vision has decreased or that they cannot see clearly and come to the ophthalmology department, only to find out after examination and diagnosis that it is not just an eye disease but a systemic disease such as diabetes, hypertension, leukemia, renal failure, intracranial tumor, etc. The eye is the window to the soul, and the eye is also the window to the whole body, because through this window, several common systemic diseases can be detected or helped to diagnose. Two common diseases, diabetes and hypertension, can both affect the fundus of the eye and even lead to blindness. Diabetes affects all parts of the eye, for example, diabetics are prone to mydriasis, conjunctivitis, keratitis, lacrimal sacitis, cataracts, corneal epithelial peeling, and may also develop diabetic optic neuropathy, diabetic eye muscle paralysis, and neovascular glaucoma. Diabetic retinopathy (referred to as glycoplasty) is the most serious complication of diabetic eye disease and one of the major causes of blindness. About 40% of diabetic patients older than 40 years of age have glycoplegia. The majority of diabetic patients are elderly, and when they have some slight changes in their eyes, they often mistake it for a normal decline or cataract. In addition, most diabetic retinopathy starts from the mid-peripheral part of the retina. When the macula is not involved, there is no obvious effect on vision, and there can be no symptoms, and clinically there are many diabetic patients who have never had an eye examination because they have no symptoms, and when they come back for examination after vision loss, they are already in advanced stage, which makes treatment difficult and ineffective. There are also many patients who go to check their blood sugar only because they have eye problems and the ophthalmologist suspects that they are caused by diabetes, but it turns out that they already have very serious complications. Therefore, we recommend that diabetic patients do not go to the ophthalmologist based on whether they can see well or not. Experts recommend that diabetic patients should go to the ophthalmology department for a dilated fundus examination immediately from the time of diagnosis, and at least once every three months if they are already showing signs of the sugar network, and once a year if they are not showing signs of the sugar network for the time being. If symptoms such as loss of vision, black shadows in front of the eyes, distorted, small or obscured vision, eye redness, eye pain, etc. have occurred, then diabetic eye disease may have developed and should be examined in detail by an ophthalmologist as soon as possible. Ophthalmology OCT is a non-invasive eye examination which is very helpful for early detection of macular edema caused by diabetes and is often more accurate than the doctor’s naked eye judgment. Another commonly used invasive test is fundus fluorescence angiography, which is based on imaging the blood vessels in the fundus to detect lesions that are difficult to see with the naked eye, such as vascular leakage, neovascularization and areas of retinal ischemia. The doctor needs to determine the severity of the lesion based on the results of the fundus fluoroscopic angiography in order to determine whether laser treatment is needed. Mild to moderate non-proliferative glucose reticulum can be treated conservatively with oral medications to improve microcirculation and neuroprotection. Severe non-proliferative and proliferative glycogen reticulums require total retinal photocoagulation. The purpose of total retinal photocoagulation is to control the progression of diabetic retinopathy. However, short-term transient vision loss may occur after total retinal photocoagulation, which may also cause some damage to the visual field, but in the long run it is beneficial for disease control and vision maintenance. Timely laser treatment can prevent 95% of diabetic blindness, so the timing of laser treatment is very important for the patient’s prognosis. Vitrectomy is required for those with vitreous hemorrhage or retinal detachment that has caused retinal detachment to help restore and maintain the patient’s vision. Diabetic macular edema is also a major cause of vision loss. The newly emerged anti-VEGF drugs have achieved good results in treating diabetic macular edema, which can effectively improve patients’ vision and stop vision loss. The downside of this treatment, however, is that it usually requires several repeat injections to achieve optimal results. Hypertension, like diabetes, can also cause fundus hemorrhage, exudation, retinal atherosclerosis, retinal vein occlusion, vitreous hemorrhage, and macular edema. The examination also requires fundus fluoroscopic angiography and OCT, and the treatment is laser, surgery, and medications. Systemic diseases such as anemia, leukemia, hyperthyroidism, kidney disease, and craniosynostosis may all manifest themselves in the fundus. In addition, scientists have said that routine eye tests may be able to “warn” of the onset of Alzheimer’s disease 20 years in advance, there is an inextricable link between the photoreceptor nerve cells of the human retina and brain cells, and the degree of damage to the former “reflects” the latter’s The degree of damage to the former “reflects” the state of decay of the latter. The fundus is the only part of the eye where arteries, veins and capillaries can be directly and centrally observed by the naked eye, and a fundus examination can predict the health status of the whole body.