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Microbiologic yields and complication rates of vitreous needle aspiration versus mechanized vitreous biopsy in the Endophthalmitis Vitrectomy Study.

PURPOSE
To compare the microbiologic yields and complication rates associated with vitreous needle tap and vitreous biopsy in the Endophthalmitis Vitrectomy Study (EVS).


METHODS
Of 420 EVS patients with postoperative endophthalmitis, 201 received immediate vitreous tap or biopsy (without pars plana vitrectomy) by random assignment and 193 completed 9-12 months of follow-up. Vitreous specimens were obtained by biopsy with a 20-gauge vitrectomy cutting instrument or by needle tap with a 22-27-gauge needle. If resistance to aspiration by needle tap was noted, a vitreous biopsy was performed.


RESULTS
Of 201 patients undergoing tap or biopsy, 70 (35%) had needle tap, 127 (63%) had mechanized biopsy, and 4 (2%) had initial needle tap that was aborted to mechanized biopsy ("abort" eyes). Intraoperative hyphema occurred in 2 tap eyes (3%), 3 biopsy eyes (2%), and 0 (0%) abort eyes. Postoperative retinal detachment developed in 8 (11%) tap eyes, 10 (8%) biopsy eyes, and 0 (0%) abort eyes (not significant). Respective rates of culture and gram stain positivity were 69% and 42% in tap eyes and 66% and 41% in biopsy eyes (not significant). The rate of severe visual loss (final acuity <5/200) was significantly higher in tap eyes (16 eyes, 24%) compared with biopsy eyes (13 eyes, 11%) and abort eyes (0 eyes, 0%; P = 0.043). The difference was largely explained by the greater proportion of virulent organisms in the tap eyes compared with biopsy eyes. When visual acuity outcome was defined by other thresholds (20/40 and 20/100), the difference was not significant.


CONCLUSIONS
This study showed no significant differences between mechanized vitreous biopsy and needle tap with respect to microbiologic yield, operative complications, short-term (9-12 months) retinal detachment risk, or visual outcome. Choice of vitreous sampling procedure must depend on the clinical judgment of the surgeon.