He hasn’t been to the doctor’s office? Is this painful for him or this busted vessel doesn’t hurt at all?
Did he notice some changes in his vision?
If answer to these questions is yes he should seek medical attention at once. Using Visine for treating burst eye vessel isn’t such a good idea because it is mostly used for treating red and dry eyes.
The only thing he can do is to increase intake of vitamin C because it helps strengthen the walls of the little blood vessels. If this condition lasts more than ten days he should contact your doctor and even if he doesn’t experience any of the unpleasant symptoms. Keep us posted about his condition.