There is a lack of knowledge about why and how atrophy spreads over time Choroidal neovascularisation (CNV) and geographic atrophy (GA) of the retinal pigment epithelium (RPE) are the two forms of advanced age related macular degeneration (AMD), the major cause of severe central visual loss in white people aged 60 and older.1 Clinical and histopathological studies in the 1970s laid the foundation for our understanding that CNV and GA are both part of the same basic disease process.2–4 The two conditions share similar ophthalmoscopic risk factors for their development. Both are more likely in eyes with large drusen or many intermediate drusen, and in eyes with pigmentary abnormality. There may be overlap of the two conditions within patients and sometimes within a single eye. Patients may have CNV in one eye and GA in the fellow eye. They may have GA in an eye and then develop CNV in that eye.5–7 They may have CNV in an eye, which on involution takes on the appearance of GA.8,9,10 They may have an evanescent form of CNV which leaves what appears as “pure” GA in its wake.7,11 Histopathologically, there is often CNV present in cases that have been diagnosed as having “pure” GA.3,12 In this issue of the BJO , Sarks and co-authors (p 442) report their findings, in 20 eyes of 18 patients, of the development of progressive atrophy of the RPE around disciform scars from …