Can a person with high myopia sprint? By sprint, I mean normal 100m and 200m sprints. And by high myopia, I mean people with -6 diopters and above. Will this increase the chance of getting a retinal detachment?
Absent any underlying pathology, there shouldn't be a risk with sprinting and high myopia. There are classifications in the Paralympic games that cover this in various athletic events.
As long as the sport doesn't involve head/face impact (Such as boxing, full contact martial arts, MMA, etc), there should be no appreciable increase in retinal detachment risks.
There is a question/opinion posting on the American Academy of Ophthalmology site with the same question:
The incidence of retinal detachment during one's lifetime for an otherwise normal eye is approximately 1 in 20,000. The risk in a highly myopic (nearsighted) individual is elevated by approximately 10 times, but still remains well under 1 percent. Several studies have supported the finding that LASIK or PRK does not increase the incidence of retinal detachment.
Exercise is important and an integral part of a healthy lifestyle. The intense cardio work-outs and weight training that you mentioned are excellent forms of exercise. Exercises to be avoided for highly myopic individuals would be those involving direct head or eye trauma such as would be inevitable in boxing. Kickboxing using the bag (as you described) without direct head trauma would be an acceptable form of exercise for a highly myopic individual. In fact, almost any form of exercise could be considered safe from an ophthalmic perspective as long as proper eye protection is observed.
I would still consult with your ophthalmologist, but there should be no increased risk from the exercising you are describing.