Medicare rules don't allow billing for the operating microscope with this code. Commercial payers may have other rules, but all of the payers I've worked with generally follow these same guidelines.
"The Internet-Only Manual (IOM), Medicare Claims Processing Manual, Publication 100-04, Chapter 12, Section 20.4.5 (Allowable Adjustments) limits the reporting of use of an operating microscope (CPT code 69990) to procedures described by CPT codes 61304-61546, 61550-61711, 62010-62100, 63081-63308, 63704-63710, 64831, 64834-64836, 64840-64858, 64861-64870, 64885-64891 and 64905-64907. CPT code 69990 should not be reported with other procedures even if an operating microscope is utilized. CMS guidelines for payment of CPT code 69990 differ from CPT Manual instructions following CPT code 69990. The NCCI bundles CPT code 69990 into all surgical procedures other than those listed in the Medicare Claims Processing Manual."