diff --git a/invesalius/data/measures.py b/invesalius/data/measures.py
index a8a9798..5e6199b 100644
--- a/invesalius/data/measures.py
+++ b/invesalius/data/measures.py
@@ -490,6 +490,7 @@ class LinearMeasure(object):
         a.GetPositionCoordinate().SetCoordinateSystemToWorld()
         a.GetPositionCoordinate().SetValue(x,y,z)
         a.GetProperty().SetColor((0, 1, 0))
+        a.GetProperty().SetOpacity(0.75)
         self.text_actor = a
 
     def GetNumberOfPoints(self):
diff --git a/invesalius/data/styles.py b/invesalius/data/styles.py
index b79553b..4bb3b88 100644
--- a/invesalius/data/styles.py
+++ b/invesalius/data/styles.py
@@ -389,7 +389,7 @@ class LinearMeasureInteractorStyle(DefaultInteractorStyle):
                                       ((x, y,z), const.LINEAR,
                                        ORIENTATIONS[self.orientation],
                                        slice_number, self.radius))
-                self.viewer.interactor.Render()
+                Publisher.sendMessage('Reload actual slice %s' % self.orientation)
 
     def OnReleaseMeasurePoint(self, obj, evt):
         if self.selected:
@@ -405,7 +405,8 @@ class LinearMeasureInteractorStyle(DefaultInteractorStyle):
                 mr.SetPoint2(x, y, z)
                 m.points[1] = x, y, z
 
-            self.viewer.interactor.Render()
+            m.value = mr.GetValue()
+
             Publisher.sendMessage('Reload actual slice %s' % self.orientation)
             self.selected = None
 
@@ -423,7 +424,6 @@ class LinearMeasureInteractorStyle(DefaultInteractorStyle):
                 mr.SetPoint2(x, y, z)
                 m.points[1] = x, y, z
 
-            self.viewer.interactor.Render()
             Publisher.sendMessage('Reload actual slice %s' % self.orientation)
 
     def CleanUp(self):
@@ -441,12 +441,20 @@ class LinearMeasureInteractorStyle(DefaultInteractorStyle):
 
     def _verify_clicked(self, x, y, z):
         slice_number = self.slice_data.number
+        sx, sy, sz = self.viewer.slice_.spacing
+        if self.orientation == "AXIAL":
+            max_dist = 2 * max(sx, sy)
+        elif self.orientation == "CORONAL":
+            max_dist = 2 * max(sx, sz)
+        elif self.orientation == "SAGITAL":
+            max_dist = 2 * max(sy, sz)
+
         if slice_number in self.measures.measures[self._ori]:
             for m, mr in self.measures.measures[self._ori][slice_number]:
                 for n, p in enumerate(m.points):
                     px, py, pz = p
                     dist = ((px-x)**2 + (py-y)**2 + (pz-z)**2)**0.5
-                    if dist < 2:
+                    if dist < max_dist:
                         return (n, m, mr)
         return None
 
diff --git a/invesalius/data/viewer_slice.py b/invesalius/data/viewer_slice.py
index 3974599..212a8dc 100755
--- a/invesalius/data/viewer_slice.py
+++ b/invesalius/data/viewer_slice.py
@@ -19,6 +19,7 @@
 #    detalhes.
 #--------------------------------------------------------------------------
 
+import collections
 import itertools
 import tempfile
 
@@ -172,7 +173,7 @@ class Viewer(wx.Panel):
         self.orientation_texts = []
 
         self.measures = measures.MeasureData()
-        self.actors_by_slice_number = {}
+        self.actors_by_slice_number = collections.defaultdict(list)
         self.renderers_by_slice_number = {}
 
         self.orientation = orientation
@@ -1178,9 +1179,9 @@ class Viewer(wx.Panel):
         image = self.slice_.GetSlices(self.orientation, index,
                                       self.number_slices, inverted, border_size)
         self.slice_data.actor.SetInputData(image)
-        for actor in self.actors_by_slice_number.get(self.slice_data.number, []):
+        for actor in self.actors_by_slice_number[self.slice_data.number]:
             self.slice_data.renderer.RemoveActor(actor)
-        for actor in self.actors_by_slice_number.get(index, []):
+        for actor in self.actors_by_slice_number[index]:
             self.slice_data.renderer.AddActor(actor)
 
         for (m, mr) in self.measures[self.orientation].get(self.slice_data.number, []):
@@ -1247,10 +1248,7 @@ class Viewer(wx.Panel):
             for actor in actors:
                 self.slice_data.renderer.AddActor(actor)
 
-        try:
-            self.actors_by_slice_number[n].extend(actors)
-        except KeyError:
-            self.actors_by_slice_number[n] = list(actors)
+        self.actors_by_slice_number[n].extend(actors)
 
     def RemoveActors(self, pubsub_evt):
         "Remove a list of actors"
--
libgit2 0.21.2