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Editors Selection IGR 9-4
Surgical Treatment: Trabecular bypass stent
Comment by Keith Barton on:
23915 Coexistent primary open-angle glaucoma and cataract: Interim analysis of a trabecular micro-bypass stent and concurrent cataract surgery, Spiegel D; Wetzel W; Neuhann T et al., European Journal of Ophthalmology, 2009; 19: 393-399
Spiegel et al. (926) report a multicenter prospective clinical series of the outcomes of 42 eyes that underwent implantation of a trabecular micro-bypass stent at the time of cataract surgery. The reported results represent an interim analysis of a 24-month study. The data are somewhat confusing as 58 patients were recruited, of whom 48 were enrolled. However, the table of demographics lists only 47 patients. What happened to number 48? Only 42 are analyzed. Two had died and two missed the 12-month visit, However, a further two who subsequently required trabeculectomy were not included in the analysis, adding potential bias to the results. There is no survival analysis or scattergram, so it is difficult to appreciate the pressure changes exhibited by each individual patient. Likewise, the graphs give means without error bars.
It is especially difficult to draw conclusions from a non-comparative study if the procedure is an adjunct to cataract surgery, because of the well-known pressure-lowering effects of cataract surgery. Clearly some effect in IOP-lowering is visible as the patients have both lower mean IOP and a lower number of glaucoma medications. The authors state in the discussion that the IOP-lowering demonstrated was greater than that for cataract surgery alone. However, reported IOP-lowering after cataract surgery is variable and may be quite large in cases of exfoliation.
Unfortunately any difficulty in estimating the proportion of pressurelowering that is due to the micro-bypass stent caused by the lack of a control group, is exacerbated by the very minimalist and at times contradictory presentation of the data.
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