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E.M. Messmer, D.M. Zapp, M.J. Mackert, M.J. Thiel, A. Kampik; In vivo Confocal Microscopy of Filtering Blebs Following Trabeculectomy . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1218.
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Purpose: The meticulous evaluation of filtering blebs after glaucoma surgery is of utmost importance to detect early scarring and initiate appropriate therapy. The Rostock Cornea Modul (RCM)/Heidelberg Retinograph (HRTII) system operates with a 670 nm diode laser and therefore allows visualization of the conjunctiva in a resolution up to 1 µm. Methods: Confocal in vivo microscopy was performed in 49 filtering blebs of 42 patients aged 24–90 years (ø 68 yrs.) 6 days to 30 years (ø 32 months) after surgery using the RCM/HRTII. Between 62 and 608 images (ø 163 images) were obtained of each bleb. One to 3 exams were performed in each patient. Pictures were analyzed by a masked observer and compared to the functional outcome of the surgical procedure. Postoperative filtering bleb function was judged as "good" (target pressure without medication; 31 eyes), "moderate" (target pressure with medication; 9 eyes) and "insufficient" (target pressure not reached or only reached with systemic acetazolamide; 9 eyes). Results: Epithelial microcysts were visible in all filtering blebs, however, significantly less microcysts were observed in blebs with insufficient function. Up to 4 months postoperatively, lymphocytes infiltrated the epithelial microcysts, the epithelium itself, and the subepithelial stroma. In the conjunctival stroma, blebs with good function showed either large pores surrounded by collagenous septae or a loose meshwork of collagen fibers with single fibroblasts. Single, mainly straight vessels were observed subepithelially and in the deep stroma. In the contrary, filtering blebs with insufficient function exhibited encapsulated cysts in the conjunctival stroma. Moreover, multiple tortuous vessels were present. Surgery using Mitomycin C led to filtering blebs with a decreased collagen network enclosing large cystic spaces without vascularization. Conclusions: In vivo confocal microscopy using the RCM/HRTII allows the visualization of filtering blebs following trabeculectomy and permits to differentiate between filtering blebs with good and insufficient function. Moreover, the postoperative inflammatory infiltrate can be monitored directly. Thus, in vivo confocal microscopy enables adapted postoperative antiinflammatory treatment and early detection of bleb failure.
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