Sir, I am writing this letter in regard to a patient in whom I placed a left sided inferior dental nerve block in order to carry out a crown preparation of an LL7. The first block did not take fully so therefore I placed a second block which was placed higher.

As half the anaesthetic went in the patient complained of double vision and flashing lights which turned from being dark purple to a light purpley haze.

I immediately stopped the injection and tried to reassure the patient. On examining her right eye, the eye was looking mesially, possibly compensating for blocking one of the nerves to the left eye muscles.

I was wondering if anybody else has had this phenomenon with colour and flashing lights. I was under the impression that the optic nerve was involved in vision and I was not aware from doing anatomy many years ago that a dental anaesthetic could block this nerve! In fact I feel there must be another reason why this occurrence happened. We carried on with the crown prep after reassuring the patient and after 15 minutes things settled back to normal.