The diagnostic yield of vitrectomy specimen analysis in chronic idiopathic endogenous uveitis

PURPOSE

The low diagnostic yield of vitrectomy specimen analysis in chronic idiopathic uveitis (CIU) has been related to the complex nature of the underlying disease and to methodologic and tissue immanent factors in older studies. In an attempt to evaluate the impact of recently acquired analytic methods, the authors assessed the current diagnostic yield in CIU.

METHODS

Retrospective analysis of consecutive vitrectomy specimens from patients with chronic endogenous uveitis (n = 56) in whom extensive systemic workup had not revealed a specific diagnosis (idiopathic) and medical treatment had not resulted in a satisfying clinical situation. Patients with acute postoperative endophthalmitis served a basis for methodologic comparison (Group 2; n = 21).

RESULTS

In CIU, a specific diagnosis provided in 17.9% and a specific diagnosis excluded in 21.4%. In 60.7% the laboratory investigations were inconclusive. In postoperative endophthalmitis, microbiological culture established the infectious agent in 47.6%. In six of eight randomly selected cases, eubacterial PCR identified bacterial DNA confirming the culture results in three, remaining negative in two with a positive culture and being positive in three no growth specimens. A double negative result never occurred, suggesting a very high detection rate, when both tests were applied.

CONCLUSIONS

The diagnostic yield of vitrectomy specimen analysis has not been improved by currently routinely applied methods in recent years in contrast to the significantly improved sensitivity of combined standardized culture and PCR analysis in endophthalmitis. Consequently, the low diagnostic yield in CIU has to be attributed to insufficient understanding of the underlying pathophysiologic mechanisms.

Automated surgical equipment requires routine disinfection of vacuum control manifold to prevent postoperative endophthalmitis

PURPOSE

Contamination of automated surgical equipment is a potential source of postoperative endophthalmitis. The effect of disinfecting the unsterile vacuum control manifold (VCM) on contamination of the aspiration fluid was studied.

DESIGN

Comparative prospective microbiologic contamination study. SPECIMENS AND CONTROLS: The 37 aspiration fluid specimens studied or examined consisted of 25 from three automated evacuation systems equipped with an internal VCM (experimental groups) and 12 from one system equipped with a modified external VCM (control group). In addition, the tubings of two internal VCMs were investigated.

METHODS

We investigated aspiration fluid specimens from routine cataract and vitrectomy operations performed with automated evacuation systems. After tracing the source of contamination to the internal VCM, the system was modified, creating an external VCM with the possibility for disinfection, and the study was continued. Whereas no sterilizing rinsing procedures were applied to the hidden internal VCM, the modified external VCM was regularly rinsed and filled overnight with 70% isopropanol. All samples were collected under sterile conditions, centrifuged, and cultured for bacterial growth on blood agar and MacConkey agar for 24 to 48 hours at 37 degrees C. The samples of the two internal VCMs were cultured for fungi as well.

MAIN OUTCOME MEASURES

Bacterial growth was quantified, and bacteria and fungi were isolated and identified according to standard microbiologic procedures.

RESULTS

In all aspiration fluid specimens from internal VCM-systems, 2+ to 4+ bacterial growth was found. Pseudomonas-related genera (Stenotrophomonas maltophilia, 17x; Comamonas acidovorans, 8x; Chryseomonas spp., 3x), Agrobacterium radiobacter (1 3x), Flavobacterium spp. (3x), and Micrococcus luteus (7x) were found most frequently. The tubing of the two VCMs contained biofilms exhibiting several of these bacteria and fungi. All specimens from the modified external VCM-system remained sterile. There was a significant difference with regard to the frequency of contamination of the aspiration fluid between the experimental and control groups (chi-square: P = 0.0001).

CONCLUSIONS

The technical modification described herein allows facile hygienic measures, by which contamination of aspiration fluid by the VCM can be eliminated, which otherwise can be a significant source of contamination.