The main causes of visual darkness are the following: 1. cataracts, gradual aging of the lens in the elderly, protein denaturation in the crystal, the original transparent lens gradually becomes cloudy, decreasing translucency, making the contrast sensitivity or vision loss. 2. central pulpy chorioretinopathy, macular edema, apparent impairment of the function of the optic rod cells, causing visual darkness and smallness. Central pulp is self-limiting but prone to recurrence, and the disease course repeatedly will leave residual symptoms of dimness of vision, and laser or photodynamic therapy can be performed if necessary.3. Retinitis pigmentosa, a hereditary disease of abnormal photoreceptor cell function, with poor night vision and progressive reduction of visual field, has no effective treatment yet.4. After total retinal photocoagulation, the retinal pigment epithelium function is partially impaired, which may cause The symptoms of darkening of vision, so the energy of the laser must be grasped.