Current status Diode laser transscleral cyclophotocoagulation (TSCP, or cyclodiode as it is commonly known in the United Kingdom), has become a popular minimally invasive treatment for glaucoma. Initially this modality was used only in eyes with advanced end stage glaucoma and with little or no visual potential, where most other surgical treatments had been tried and failed. This was because of traditional mistrust of earlier cycloablation methods, such as cyclocryotherapy, that were associated with a higher incidence of serious complications than TSCP. As confidence and experience of TSCP grows it is now being safely applied increasingly earlier in the glaucoma treatment paradigm and in eyes with greater visual potential1; it has even been suggested that TSCP be used as a one off primary treatment for glaucoma in developing nations with poor access to reliable medical and surgical follow up. There is still, however, considerable local and regional variation in the use of this treatment (anecdotal impressions suggest that it is used more commonly and earlier for glaucoma treatment in the United Kingdom than in the United States), perhaps in part because of the relative paucity of high quality laboratory and clinical studies demonstrating if, why, and how it is effective. There is even less evidence concerning endoscopic cyclophotocoagulation (ECP), the more refined but less widely available cousin of TSCP. In the April issue of the BJO , Lin et al published an important laboratory based study that adds to our understanding of the clinical effects and complications of cyclophotocoagulation (CP).2 They have attempted to quantify the evolution of vascular changes following CP; their results demonstrate that both TSCP and ECP are associated with an acute occlusive vasculopathy, but that with the endoscopic modality the chronic underperfusion is less than with the transscleral route. The effects of CP …