The problem seems to begin with the Husserlian bracketing of the natural attitude. The perceptive field is organised as a function of a situated intentional consciousness that is open to the world.
Visual sensation is in our heads.
Obviously, the physiologist doesn't understand, nor can understand, given the objectivist method of science, and he deludes himself if he thinks that in speaking of integration, chronaxie, of scanning or gestalt - he can understand the transformation of neuronal action into a conscious field of vision. One can admit with phenomenology that it is consciousness that gives meaning to the very notion of 'world'. A leibnizian theoretical biology. Paradoxically the 'wide-openness' is in our brains but not our brains as the objects of science. An inobjectifiable brain.