Scar tissue on the ear drum is usually caused by repeated ear infections. The scar tissue can lead to difficulty hearing and eventually ruptured ear drums. Surgery is one means of avoiding progressive hearing loss or ear drum rupture. No patients have reported taking Scar tissue removal (eardrum).
USCIS normally responds to RFE's within 60 days, however they do not have processing times on how long it takes them to respond. It can be longer than that. I would call the USCIS number: 1 (800) 375-5283 and submit a service request, if you do not hear from them soon.
It is perfectly acceptable to ask a guest to respond four weeks before the wedding. Allow three or four days for any cards that were mailed on the deadline, and begin making your phone calls to find out about the stragglers.