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How to find out which eye is producing the peripheral image in Diplopia?

Ask the patient to cover both eyes one by one-alternatively; ask him to notice the side of the eye, closure which results in disappearance of the periphera image. But it is tricky and patients sometimes wont be able to tell. Best and easy way is as bellow.

Red-Glass test

  1. Put a red glass in front of one eye: usually right eye.
  2. Now patient sees the image produced by the right as red.
  3. Ask patient to notice color of the peripheral image, ie normal or red.
  4. If red one is to the periphery, then the right eye is the culprit.
  5. If the normal image is to the periphery, left eye is the culprit.