The module does not work if drupal is installed in a subdirectory. The error I saw was from (eyedrop/editor/jquery.eyedrop.js, line 348):

  /**
  * Image save
  */
  eye.editSubmit = function () {
    $.post("/eyedrop/request/eyefield_save_parameters/"+params['nid']+"/"+params['size'],
      { x: (dsp['X'].value / zoom), y: (dsp['Y'].value / zoom), w: (dsp['W'].value / zoom), h: (dsp['H'].value / zoom) },

There may be other places where direct path is used, but I haven't looked for them.