Yes, you can joined CBI as SI if you have minus 6 spectacles. No problem at all! just be active enough to walk a couples of KMS and cycle fast for the final selection (After Tier 3 exam). Be relaxed and just concentrate on gaining more knowledge on the subject and practice well. Vision:- Eye-sight (with or without glasses) . Distant vision:- 6/6 in one and 6/9 in the other eye.