H49.1: Fourth [trochlear] nerve palsy

The muscles in your eye are no longer working properly due to a nerve being damaged.

Muscles around the eye control eye movement. These muscles receive signals from the brain in order to perform these movements. These signals are transmitted by nerves. Some muscles in the eye have additional functions. They include lifting the eyelids and narrowing the pupils.

In your case, a nerve controlling the eye muscles is damaged. This kind of damage means that the eye muscles stop working normally and that you can no longer move the eye properly. The affected eye may be pointing down when looking straight ahead or to the side, for example. You may also have double vision. For some people, double vision gets better when they turn their head in a certain direction. These people may often hold their head tilted to one side.

Additional indicator

On medical documents, the ICD code is often appended by letters that indicate the diagnostic certainty or the affected side of the body.

  • G: Confirmed diagnosis
  • V: Tentative diagnosis
  • Z: Condition after
  • A: Excluded diagnosis
  • L: Left
  • R: Right
  • B: Both sides

Further information


This information is not intended for self-diagnosis and does not replace professional medical advice from a doctor. If you find an ICD code on a personal medical document, please also note the additional indicator used for diagnostic confidence.
Your doctor will assist you with any health-related questions and explain the ICD diagnosis code to you in a direct consultation if necessary.


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