Điều này có thể xuất hiện dao động. Nếu tách rời trên, các xâm phạm bóng từ bên dưới và nó có vẻ cải thiện một cách tự nhiên với bedrest, lúc đầu tốt hơn vào buổi sáng. Mất thị lực trung tâm hoặc làm mờ hình ảnh xảy ra khi các hố mắt là tham gia bằng cách tách rời | Retinal Detachment 107 after a variable period between days and years a black shadow is seen encroaching from the peripheral field. This can appear to wobble. If the detachment is above the shadow encroaches from below and it might seem to improve spontaneously with bedrest being at first better in the morning. Loss of central vision or visual blurring occurs when the fovea is involved by the detachment or the visual axis is obstructed by a bullous detachment. Inspection of the fundus at this stage shows that fluid seeps through the retinal break raising up the surrounding retina like a blister in the paintwork of a car. A shallow detachment of the retina can be difficult to detect but the affected area tends to look slightly grey and most importantly the choroidal pattern can no longer be seen. The analogy is with a piece of wet tissue stuck against grained wood. If the tissue paper is raised slightly away from the wood the grain is no longer visible. As the detachment increases the affected area looks dark grey and corrugated and the retinal vessels look darker than in flat retina. The tear in the retina shines out red as one views the RPE and choroid through it. Once a black shadow of this kind appears in front of the vision the patient usually becomes alarmed and seeks immediate medical attention. Urgent admission to hospital and retina surgery are needed. Tractional Retinal Detachment In tractional retinal detachment the retina can be pulled away by the contraction of fibrous bands in the vitreous. Photopsiae and floaters are usually absent but a slowly progressive visual field defect is noticeable. The detached retina is usually concave and immobile. Advanced proliferative diabetic retinopathy can be complicated by tractional retinal detachment of the retina when a contracting band tents up the retina by direct traction. Not infrequently such a diabetic patient experiences further sudden loss of vision in the eye when the traction exerted by the contracting .
