using three approaches - one single-center trial employed sectoral scatter laser photocoagulation using an argon laser; and in the second, two-center trial focused on feeder vessel coagulation, one center used an argon laser and the other used a xenon arc laser. Based on weak evidence, it appears that laser coagulation may be effective in preventing visual loss and vitreous haemorrhage in this condition but that it does not have an effect on regression of proliferative sickle retinopathy or preventing the development of new vessel growth. Radiation proctitis When radiation therapy is administered to treat cancers like cervical cancer, prostate cancer, and colon cancer, radiation proctitis can occur, which involved chronic bleeding in the colon. Treatment with Nd:YAG lasers and with Nd:YAG laser passed through a Potassium titanyl phosphate crystal, and with an argon laser has been studied in small clinical trials. Nd:YAG laser has been abandoned due to risks of damaging the colon wall, fibrosis, stricture formation, and recto-vaginal fistula, and severe damage in case of accidents, as well as the cost. The other two modalities were largely replaced by argon plasma coagulation by 2011, which was safer and less expensive. Complications In the eye, side effects and complications of laser photocoagulation are not infrequent and include loss of vision, worsening visual acuity, reduced night vision, and hemorrhaging in the eye. In about 8% of cases can cause scarring which in turn can lead to permanent central vision loss. History German ophthalmologist, Gerhard Meyer-Schwickerath is widely credited with developing the predecessor of laser coagulation, photocoagulation. In 1946, he started conducted the first experiments on light coagulation. In 1949, he performed the first successful treatment of a retinal detachment with a light beam (light coagulation) using a self-constructed device on the roof of the ophthalmic clinic at the University of Hamburg-Eppendorf. Results of using laser coagulation to treat diabetic retinopathy were first published in 1954. Conventional macular focal and grid laser photocoagulation were established as the treatment of choice for diabetic macular edema in the Early Treatment Diabetic Retinopathy Study (ETDRS), which published in 1985. See also List of laser articles References Lawrence, Peter F; Bell, Richard M; Dayton, Merril T (2006). Essentials of Surgical Specialties. Lippincott Williams & Wilkins. Laser medicine Eye procedures