If you zoom in on those photos, you can see that the camera images entire lines of text at the same resolution. A camera can 'read' the entire chart in one snapshot.
The eye doesn't work that way. For example, it is anisotropic in resolution; at the fovea, it has more 'pixels', but away from it, it has way fewer. Effect? You cannot read a line from a Snellen chart without moving your eyes. The eye doesn't take snapshots.
The point is that the eye has the effective resolution, in terms of reading an eye chart, of a 10MP camera.