Check the Medicare fee schedule for important bilateral coding guidelines for 673xx. Let Modifier 50 Spring You From 67312 Trap Scenario: Be careful: The strabismus surgery codes (67311-67318) describe unilateral procedures or procedures performed on one eye only, explains Maggie M. Mac, CPC, CEMC, CHC, CMM, ICCE, director of Best Practices-Network Operations at Mount Sinai Hospital in New York City. Although the surgeon did resect two muscles, they were in different eyes, so 67312 is not correct. Instead, you should report 67311 (Strabismus surgery, recession or resection procedure; one horizontal muscle) bilaterally. Most Medicare carriers want you to report the entire session on one line with modifier 50 (Bilateral procedure) and a "1" in the units field. Warning: You can use modifier 50 for that particular code and expect to receive 150 percent payment, says Denise Stanton, CPC, CCP-P, senior coding analyst at Beth Israel Deaconess Medical Center in Boston. If you report 67311-50 or two instances of 67311 on two lines -- for example, 67311-LT for the left eye and 67311-RT-51 (Multiple procedures) for the right -- Medicare will base payment on 150 percent of the fee schedule amount for a single code. Medicare multiplies the facility relative value units (RVUs) for 67311 (15.06) by the conversion factor of 36.0846, arriving at $543.43. Appending modifier 50 for the bilateral procedure means that Medicare would reimburse you 150 percent of that, giving you $815.15 (unadjusted for geographical location). Reporting 67312, however, even though the descriptor mentions "two horizontal muscles," will short-change you. With no bilateral pay adjustment, the RVUs for 67312 would only bring in $657.46. "And the bottom line is that it is an incorrect code to report since it implies that two horizontal muscles in the same eye were resected, and that was not the case," notes Mac. Select a Single Code for Single-Eye Muscles To code strabismus surgery correctly, you also need to know when you should or should not appropriately report strabismus surgery bilaterally. If the ophthalmologist resects both the lateral rectus and medial rectus muscles of the left eye, it is not a bilateral procedure. This is a case for which 67312 would be appropriate. You would report 67312 when two horizontal muscles are recessed or resected in the same, eye, Mac explains. The same rules apply for the vertical muscles (the superior rectus, inferior rectus and inferior oblique muscles). Use these CPT codes for the following strabismus scenarios, based on which muscles the ophthalmologist worked on: • 67311 for one horizontal muscle in one eye • 67312 for two horizontal muscles in one eye • 67314 for one vertical muscle in one eye • 67316 for two or more vertical muscles in one eye • 67318 for the superior oblique muscle in one eye. If the ophthalmologist operates on one vertical and one horizontal muscle in one eye, however, it is correct to use two codes -- 67311 and 67314 (... one vertical muscle [excluding superior oblique]). Practice: Save Add-On Code for Special Occasions You should use add-on codes whenever the operative report clearly documents an additional procedure -- an adjustable suture, for instance -- or a complicating condition or history. A careful coder may be aware of a condition in the patient's history that the surgeon doesn't state in the operative report. You should call this fact to the physician's attention so that he can edit it in the operative report to allow billing. Requirement: For example, you can use +67320 (Transposition procedure [e.g., for paretic extraocular muscle], any extraocular muscle [specify] [list separately in addition to code for primary procedure]) with strabismus surgery codes 67311-67318, according to CPT guidelines. Likewise, you can only report the following add-on codes when applicable with codes 67311-67318: • +67331 -- Strabismus surgery on patient with previous eye surgery or injury that did not involve the extraocular muscles • +67332 -- Strabismus surgery on patient with scarring of extraocular muscles or restrictive myopathy • +67334 -- Strabismus surgery by posterior fixation suture technique, with or without muscle recession. Don't overlook: But you can only report 67320-67334 with a primary procedure code. Many trauma cases may involve multiple add-on codes -- for instance, in the case of an open globe in which the ophthalmologist would have to explore for damaged muscles and insert an adjustable suture. Watch out: