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Editors Selection IGR 17-4

Surgical Treatment: Bleb evaluation by 3DCAS-OCT

Comment by Celso Tello & Gustavo de Moraes on:

23862 Evaluation of trabeculectomy blebs using 3-dimensional cornea and anterior segment optical coherence tomography, Kawana K; Kiuchi T; Yasuno Y et al., Ophthalmology, 2009; 116: 848-855

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Kawana et al. (679) performed a well-designed and clinically relevant cross-sectional study investigating in vivo bleb morphology using a new prototype of three-dimensional anterior segment optical coherence tomography (3DCAS-OCT). The authors found that lower postopertative intraocular pressure (IOP) significantly correlated with the following bleb characteristics: horizontal and vertical length of the internal fluid-filled cavity; total bleb height and height of the internal fluid-filled cavity; maximum bleb wall thickness; volume of the internal fluid-filled cavity and hyporeflective area; and number of microcysts.

Moreover, when comparing eyes with predefined successful and failed trabeculectomies, the same parameters were significantly different between groups. In sum, the authors showed that it is possible to determine and measure in vivo, real-time morphological characteristics of filtering blebs using this new device, and that these features may provide an estimate of surgical success.

The discussion section was objective and focused on the results. The authors clearly stated some of their limitations and proposed alternatives so that these can be overcome in future studies. Nevertheless, some relevant points were not clearly mentioned or discussed in the article. There is no description of whether the image interpretation was performed in a masked fashion from IOP data or from the bleb's clinical appearance. Also, there is no reference to the repeatability of their methods between or within investigators. The cross-sectional nature of the study also prevents any conclusion regarding the predictive role of such bleb features on future surgical outcomes. Albeit that the authors did not disclose any commercial relations with the presented device, it was developed at the same institution as their group, and should be tested at different centers. These limitations notwithstanding, their results are consistent with the current literature and the common knowledge on the clinical features of functioning blebs. Yet, because they used a novel device, one cannot compare the evaluated parameters with studies that used different technologies. Despite providing a low level of scientific evidence (level: 3b), Kawana et al. showed promising results that, once reproduced and applied prospectively, could provide useful information for both clinicians and researchers who aim to investigate factors associated with the success of trabeculectomy.

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