Access by profile

/**
 * Implements hook_node_accces().
 */
function example_schedules_node_access($node, $op, $account) {
  if ($op !== 'view' && $node->type == 'class') {
    if($profile = example_account_profile($account->uid)){
      if ($profile->type == 'teacher') {
        if ($op == 'create'){
          return NODE_ACCESS_ALLOW;
        }
        $teacher = isset($node->field_teacher[LANGUAGE_NONE][0]['target_id']) ? $node->field_teacher[LANGUAGE_NONE][0]['target_id'] : 0;
        if ($teacher == $profile->nid) {
          return NODE_ACCESS_ALLOW;
        }
      }
      else {
        $venue = isset($node->field_venue[LANGUAGE_NONE][0]['target_id']) ? $node->field_venue[LANGUAGE_NONE][0]['target_id'] : 0;
        if ($venue == $profile->nid) {
          return NODE_ACCESS_ALLOW;
        }
      }
    }
  }
}