The Barcelona Institute of Science and Technology, Campus UAB 1 article published in JoVE Neuroscience Calcium Imaging In Electrically Stimulated Flat-Mounted Retinas Marina Cunquero1, Maria Marsal1, Gustavo Castro-Olvera1, Steven T. Walston2, F. Taygun Duvan2, José Gabriel Macias-Montero3, Carles Puigdengoles3, Mokhtar Chmeissani3, Jose A. Garrido2,4, Pablo Loza-Alvarez1 1Institut de Ciències Fotòniques (ICFO), The Barcelona Institute of Science and Technology, 2Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, 3Institut de Física d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 4Institució Catalana de Recerca i Estudis Avançats (ICREA) Retinal prostheses have the ability to generate visual perceptions. To advance the development of new prostheses, ex vivo methods are needed to test devices before implantation. This article provides a comprehensive protocol for studying calcium activity in the retinal ganglion cell layer when subjected to electrical stimulation.