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Diplopia Charting

Dr. Jitendra Jethani
MS, DO, DNB, FNB (Pediatric Ophthalmology & Strabismus)
Consultant
Pediatric Ophthalmology & Strabismus Clinic
T V Patel Eye Institute
Salatwada, Vadodara- 390001

 

Diplopia chart is the record of separation of the diplopic or double images in the nine positions of gaze. It can be plotted charted in patients who cooperate and can appreciate double vision and with incomitant or comitant deviation.

The method
The patient should be comfortable with his head erect and should preferably be still throughout the examination. The test is preferably carried out in a dark room. A red glass is put in front of one of the eyes (red in front of right, R for R, is a convention). It is desirable to use Armstrong goggles since these are shaped to fit the orbital margin and therefore patient would be looking only through the colored medium. The examiner holds the torch (vertical source of light) at around ½ m or 1 m (It is important to mention the distance on the chart). This source of light could be horizontal if the complain is of vertical separation of images
The light is held directly in front of the patient at first.
If the patient sees a single image, the examiner must establish whether it is a fused image, if suppression is present or if one image is obscured, for example by patient’s nose bridge. If there is no double vision in primary position, the position in which double vision appears and is maximal is to be noted.
If the patient notes a double image, the relative position of these images is noted. The light is now carried to the right and then to the other 8 positions of gaze. In each gaze position the patient must be asked whether the images are parallel or tilted; if torsion is present colored pencils can be given to an observant patient to show the separation in torsion. Also, in each gaze patient should be asked the amount of separation subjectively and its increase in a particular gaze.

Interpretation of a diplopia chart
To interpret the diplopia chart the most important questions are

  1. The position in which diplopia appears
  2. The position in which the separation of image is the greatest

fig1

In the direction of the action of the paralyzed muscle the double vision or the separation would be greatest because of the underaction of the muscle and overaction of the antagonist muscle and yoke muscle.
Therefore, in paralysis of left lateral rectus muscle (Fig 1), the separation of images would be maximal in left gaze or levoversion.  This follows that if there is a horizontal increase in separation of images seen on the right side, the muscles which rotate the eye towards right (that is right lateral rectus and left medial rectus) would be underacting or paralyzed. If the eye deviates inwards, it will project outwards the image of an object fixed by other eye. Therefore, in the position of eyes in which the images are most widely separated, the distal image always belongs to the paralytic eye. With the help of color of image the eye (to which the images belongs) could easily be found
If the images are vertical separated, where the separation increases on downgaze, one of the depressors is involved. If the separation increases on looking down and to the left, the left hand depressors are involved (in case of paralytic strabismus) (left hand depressors would be left inferior rectus and right superior oblique).  If the image belonging to the left eye is the lower one, the left inferior rectus is involved. (Fig 1)
Importantly the images may also be tilted in vertical muscle paralysis and therefore torsion would also give valuable hint in coming to a conclusion. Therefore, if the left inferior rectus is involved, the eye would be intorted and the image seen would be extorted. The maximal torsional movement for this would be seen in the right gaze downwards. (Fig 1)

 

Diplopia chart (precautions)

  1. Head must be kept straight during the examination
  2. The goggles must be well fitting
  3. The light should be kept upright (or horizontal in case of vertical or torsional diplopia) and held at a consistent distance
  4. The patient should be asked about tilting of images
  5. The light should be visible to both the eyes
  6. Never interpret the diplopia chart in isolation, clinical examination and Hess chart should be used in conjunction to come to a conclusion

 

Diplopia chart (recording on paper)

  1. While recording the diplopia on paper the right and left is the patient’s right and left and not the examiner’s (Fig 1)
  2.  Always note the distance at which the diplopia charting was done
  3. Note the distance of separation of the images in each position as told by the patient subjectively
  4. Tilting of image is drawn as the patient describes
  5. Although the charting could be drawn from examiner’s viewpoint too, it is imperative to note it in the chart.

 

Diplopia chart (value)

  1. Only gives a picture of patient’s double vision.
  2. Maximal separation of images may give an idea about the paralyzed muscle
  3. Not very useful in recording paresis
  4. Not much helpful in diagnosis in multiple muscle pathologies

 

It is useful particularly in

  1. Torsional diplopia (especially in bilateral symmetrical superior oblique palsies)
  2. Patients who is bed ridden
  3. Patient who is otherwise incapacitated
  4. Unable to plot Hess chart
  5. Unable to plot Binocular field of fixation
  6. Diplopia chart should be interpreted with clinical findings and other investigation like binocular field of fixation, Hess chart etc.

 

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