An image sensor may include an array of image pixels arranged in rows and columns. Each image pixel arranged along a column may be coupled to a pixel column line. Each pixel column line may be coupled to column memory circuitry via a respective analog-to-digital converter circuit. The column memory circuitry may include multiple column memory circuits, including a spare column memory circuit. If none of the column memory circuits are defective, the spare column memory circuit is idle. If one of the column memory circuits is defective, the spare column memory circuit is engaged to bypass the defective column memory circuit. Configured in this way, the column memory circuitry is provided with column-wise memory repair capabilities.