repeat testing same day by different doctors office

A pt was referred to our office same day as the referring doctor performed a fundus photo. When the pt was exaimed at our facility the doctor orderd a fundus photo. the other office processed there claim before us, was told by the insurance co. that we could get paid but we had to attach a modifier to the claim. What modifier do I use? Thank You

re: repeat testing same day by different doctors office

Look at modifier 77