Methods and apparatus are disclosed for measuring and mapping oxygen tension in a tissue and, in particular, permit direct non-invasive measurement of retinal tissue oxygen tension. In one aspect, the invention is directed to methods for determining oxygen tension in a target tissue sensitized with an oxygen sensitive probe by imaging the target tissue. In one embodiment, the invention provides a noninvasive method for monitoring oxygen tension in a chorioretinal tissue sensitized with an oxygen sensitive probe. In another aspect, apparatus is disclosed that can determine oxygen tension in tissue by quantifying a signal emitted by an oxygen sensitive probe within the three-dimensional map of a tissue to determine oxygen tension and provide a three-dimensional map of oxygen tension variations.