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Editors Selection IGR 12-4

Filtering Blebs: Conjunctival microcysts by confocal microscopy

Comment by Tony Wells on:

24140 Conjunctival characteristics in primary open-angle glaucoma and modifications induced by trabeculectomy with mitomycin C: an in vivo confocal microscopy study, Ciancaglini M; Carpineto P; Agnifili L et al., British Journal of Ophthalmology, 2009; 93: 1204-1209

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Conjunctival microcysts are frequently visible on slit-lamp examination after glaucoma filtering surgery (GFS), and are generally recognized as a marker of filtration success. While microcysts are occasionally not seen in some bleb morphology variants even when trabeculectomy is working well, the converse situation of having visible conjunctival microcysts in non-operated eyes is less widely known. In this comparative case study, Ciancaglini et al. (980 ) follow up on their previous work describing confocal microscopy appearances in glaucoma, ocular hypertensive and post-trabeculectomy eyes. Where previous analyses of bleb tissue appearances using in-vivo confocal microscopy have tended to attribute unusual appearances, such as the presence and distribution of microcysts to the surgical procedure, in this study 15 patients were imaged prior to, and six weeks after trabeculectomy with MMC, and ten medically treated glaucoma patients were also imaged six weeks after a baseline examination. Imaging of microcysts was performed using the HRT II Rostock Cornea Module, with area and density of microcysts calculated using image analysis software. In some cases, a clever solution to reconstruct much larger areas of the bulbar conjunctiva than that afforded by the Rostock Cornea Module was employed: a digital camera was used to record the locations of each 300µ square window, allowing relative localisation of these very small imaging windows. The individual images could then be built into montages for each eye. The GFS patients had bleb gradings, although the results of these are not presented, but were described as all having diffuse bleb morphology. The authors found that conjunctival epithelial microcysts are also numerous and distributed widely both in eyes without prior surgery, as well as those after surgery. After surgery with MMC, there was a five-fold increase in microcyst density and area. Also of interest was the lack of inflammatory or dendritic cells in bulbar epithelium in the subjects and controls. The discussion includes interesting spe culation on the origin and implications of microcystic change in the epithelium of patients with glaucoma; this is hypothesised to be a sign of marked aqueous filtration enhancement, although it also described in ocular hypertension. The potential role of goblet cells in epithelial microcyst pathogenesis, as discussed by Amar (Amar N, Labbe A, Hamard P, et al. Filtering blebs and aqueous pathway. An immunocytological and in vivo confocal microscopy. Ophthalmology 2008;115: 1154-1161) was also discussed.

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