The report of the EVS1 described the TAP group as having undergone either needle aspiration or vitreous biopsy with a vitrectomy instrument "at the discretion of the operating surgeon." Patients in whom "an adequate sample could not be obtained" with needle aspiration also could undergo vitreous biopsy, defined as a biopsy sample of 0.1 to 0.3 mL. The article does not state how many patients had vitrectomy instrument tap for either of the above reasons, nor does it report separate results for vitrectomy-tap vs needle-tap groups. Also, were all vitrectomy taps performed in the operating room?
Because failure to get an adequate specimen with needle aspiration alone was 1 of the reasons vitrectomy was first proposed for endophthalmitis treatment, it would be interesting to know how often this failure occurred in the EVS. It is also likely that patients in the vitrectomy-tap group had significantly more vitreous removed than
Hanscom T. The Endophthalmitis Vitrectomy Study. Arch Ophthalmol. 1996;114(8):1029-1030. doi:10.1001/archopht.1996.01100140233036