Retinal detachment is the separation of the neuroepithelial layer of the retina from the pigment epithelium. There is a potential gap between the two layers, and the fluid trapped in the gap after separation is called subretinal fluid. The detached portion of the retina is unable to perceive light stimuli, resulting in incomplete or total loss of images from the eye. Signs and symptoms of retinal detachment include: (1) Flash sensation: It is the earliest symptom of retinal detachment and is essentially a symptom of retinal irritation produced by posterior vitreous detachment, with arc light-like symptoms appearing in 1-2 quadrants of the retina periphery. (2) Flying mosquitoes: It is also one of the symptoms of posterior vitreous detachment and can be caused by blood cells entering the vitreous after retinal vascular rupture. The occurrence of flash and flying mosquitoes does not necessarily have retinal detachment, but because it is often a precursor symptom of retinal detachment, it must be taken seriously, detailed fundus examination, if necessary, triple-lens examination, so as not to miss the possible retinal fissure or detachment. (3) Visual field defect and central vision loss: When retinal detachment occurs, visual field defect occurs in the direction corresponding to the first detached area, and increases with the extent of retinal detachment. The retinal site where the first visual field defect occurs is often the site of the retinal fissure, which is important when taking a medical history. When the retinal detachment involves the macula, there is a severe loss of central vision. Occasionally, patients present to the clinic with a slow progression of retinal detachment until the central vision is involved, by which time it is already an old retinal detachment.