I am high myopic (left eye is -11.25 and right eye -10.50).my left eye the last 2 years keeps going up a quarter diopter. my optometrist says so far everything looks great considering i have a high prescription.what are chances of blindness in future?

You are not at risk of going blind. Quit obsessing and see an ophthalmologist.

People who are highly myopic are at increased of retinal detachment, macular degeneration, and glaucoma so regular eye examinations by an ophthalmologist, possibly even a retinal specialist, are indicated. The slow increase in myopia is not uncommon, and on a percentage basis a 0.25 diopter change would not mean that glasses need to be updated.