Diabetic retinopathy severely affects vision and is often irreversible, and the only method recognized worldwide as effective is laser treatment. What can laser treatment do? For diabetic macular edema (the macula is the most critical part of a person’s vision), laser treatment can reduce macular edema and prevent further vision loss. From experience, some patients may have improved vision after laser treatment, but in general it is difficult to return vision to normal. For severe non-proliferative (fluorescence angiography shows signs of retinal ischemia, but no neovascularization yet) diabetic retinopathy, laser treatment aims to prevent neovascularization from occurring. For proliferative diabetic retinopathy with neovascularization, laser treatment photocoagulation of all areas of the retina beyond the macula (i.e., total retinal photocoagulation) aims to subside the abnormal neovascularization and prevent its further development. Laser treatment photocoagulation is beneficial in reducing the chance of vitreous blood accumulation and preventing the development of retinal detachment by traction and neovascular glaucoma. Diabetic retinopathy is divided into 6 stages, and only stages 3 and 4 (pre-proliferative and early proliferative stages) are suitable for laser treatment. Therefore, diabetic patients must go to the ophthalmology department regularly for fundus examination, fundus imaging, and fundus fluorescence angiography at the right time. Do not miss the best time for treatment. Laser therapy has been shown to be effective in controlling the progression of the disease, but it also has certain side effects, such as temporary blurring of vision, mild vision loss and visual field defects, and in most cases, repeated laser treatments are necessary. Although laser treatment can have the above mentioned effects, it cannot cure diabetic retinopathy, so even if total retinal photocoagulation has been completed, follow-up visits to the ophthalmology department must be adhered to. This is a fundus and fluorescence image of the preproliferative phase in both eyes. The fluorescence image shows large capillaries without perfusion and fluorescein leakage, which is an indication for laser total retinal photocoagulation, even though this patient’s visual acuity is 1.0 in the right eye. This is a combination image of total retinal photocoagulation in one eye, usually with one laser shot per week for a total of 4 weeks to complete treatment.