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.
At the end he told me, somewhat under his breath, that I can expect a response in 30-90 days. At least I think that's what he said. I know it's only been 20 days, and I don't want to seem impatient, but how long can one expect to wait until further action is needed; such as setting up an INFOPASS appointment.