An event-driven sensor comprising: - a pixel array; - a column readout circuit coupled to column output lines (204, 254) of the pixel array, the column readout circuit comprising a plurality of groups of column register cells, each group of column register cells comprising at least two column register cells, each column register cell being coupled to a corresponding one of the column output lines, the column register cells of each group being coupled in series with each other to propagate a first flag signal (FLAGx) from a first to a last column register cell of the group, wherein each column register cell is configured to activate a column event output signal (addrx) when it receives the first flag signal (FLAGx) while the detection of an event is indicated on the column output line; and - a first bypassing circuit for each group of column register cells, the first bypassing circuits being coupled in series with each other to propagate the first flag signal (FLAGx), each first bypassing circuit being configured to propagate the first flag signal (FLAGx): to the first column register cell of its group if an event is indicated on one of the column output lines coupled to one of the column register cells of the group; and to a flag output of the first bypassing circuit, bypassing the column register cells of the group, if no event is indicated on one of the column output lines coupled to one of the column register cells of the group. - a pixel array; - a column readout circuit coupled to column output lines (204, 254) of the pixel array, the column readout circuit comprising a plurality of groups of column register cells, each group of column register cells comprising at least two column register cells, each column register cell being coupled to a corresponding one of the column output lines, the column register cells of each group being coupled in series with each other to propagate a first flag signal (FLAGx) from a first to a last column register cell of the group, wherein each column register cell is configured to activate a column event output signal (addrx) when it receives the first flag signal (FLAGx) while the detection of an event is indicated on the column output line; and - a first bypassing circuit for each group of column register cells, the first bypassing circuits being coupled in series with each other to propagate the first flag signal (FLAGx), each first bypassing circuit being configured to propagate the first flag signal (FLAGx): to the first column register cell of its group if an event is indicated on one of the column output lines coupled to one of the column register cells of the group; and to a flag output of the first bypassing circuit, bypassing the column register cells of the group, if no event is indicated on one of the column output lines coupled to one of the column register cells of the group. to the first column register cell of its group if an event is indicated on one of the column output lines coupled to one of the column register cells of the group; and to a flag output of the first bypassing circuit, bypassing the column register cells of the group, if no event is indicated on one of the column output lines coupled to one of the column register cells of the group.