Ganglion cell pathways for rod vision.

Measurements of the acuity of rod vision made by two different techniques show it to vary only slightly with eccentricity. At eccentricities beyond 15 deg acuity is well predicted from the sampling properties of the mosaic of the P-class of ganglion cells. With decreasing eccentricity acuity falls progressively below the sampling limit of P-cells, but even at the lowest eccentricity examined (5 deg) does not reach the limit imposed by the sampling properties of the mosaic of M-cells. At an eccentricity of 5 deg rod vision could be supported by as few as 20% of P-cells.