Abu-al-Faraj Ibn Harun (Gregory Bar hebraeus). The book is entertaining stories (№ 221855)

The doctor asked the patient, who suffered from indigestion, the causes of the disease.
I ate burnt bread, ' replied the patient.
The doctor told him:
- I advise you to surety eyelids, it will improve your eyesight.
The patient said to him:
Not about the eyes I'm talking to you, and about the stomach.
Replied the doctor:
- I know, but I give you advice that is relevant to the vision in order for you to continue is different from burnt bread and not eat it.