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Histopathology and treatment of a huge overhanging filtering bleb
© The Author(s). 2016
Received: 18 April 2016
Accepted: 23 September 2016
Published: 6 October 2016
The giant filtering bleb encroaching onto the corneal surface is a rare occurrence in our and other’s clinical experience (Kapoor and Syed, Int. Ophthalmol 31(5):403–404, 2011), even in patients having had a trabeculectomy with mitomycin C, and how it developed is debated. In this paper, we report a patient who developed a huge overhanging filtering bleb after trabeculectomy, and present our intraoperative photographs, histopathology and immunohistochemistry results.
A 62-year-old female visited our hospital due to the giant filtering bleb encroaching onto the corneal surface which was about 6 mm × 8 mm × 3 mm. We dissected the filtering bleb from the cornea and present the histopathology and immunohistochemistry results of it.
The results from histopathology and immunohistochemistry in this study are consistent with the filtering cicatrix hypothesis. However, our finding that the overhanging blebs had tight connections with the corneal tissue or corneoscleral limbus, rather than simply leaning on it, might be highly related to their development and still needs to be further studied.
An overhanging filtering bleb is a uncommon postoperative complication of trabeculectomy , and is thought to be increasing with the greater use of antimetabolites in glaucoma filtering surgery . The term overhanging filtering blebs refers to oversized filtering blebs that project over the cornea [2–4]. Patients commonly suffer symptoms that increase with the growth of the bleb. Symptoms are constant foreign body sensation, excessive tearing, sensitivity to light and visual disturbances, and are considered to be caused by tear film instability, increased astigmatism and occlusion of the visual axis by the large blebs [2–4]. Patients also generally complain of poor cosmesis . Excision of overhanging filtering blebs is recommended for patients with seriously compromised comfort and visual function [1, 2, 5]. However, how it developed is debated. In this paper, we report a patient who developed a huge overhanging filtering bleb after trabeculectomy, and present our intraoperative photographs, histopathology and immunohistochemistry results, and discussed about the mechanism of overhanging blebs formation.
Overhanging blebs can occur days  to years  after the procedure in patients from 12 to 82 years old [4, 6] and their incidence appears to be increasing with the current liberal use of antimetabolites in glaucoma filtering surgery [2, 7]. The giant filtering bleb encroaching onto the corneal surface of this patient was about 6 mm × 8 mm × 3 mm, which is a uncommon occurrence in our and other’s clinical experience [8, 9]. In our patient, the conjunctiva of the bleb was fragile (Fig. 2i), which may have been the result of MMC application during her trabeculectomy.
How overhanging blebs develop is debated. Sheie et al.  hypothesize that an overhanging bleb is a filtering cicatrix that has been massaged downward over the cornea by the action of the eyelid, and that the bleb is in contact only with the cornea surface. To test whether scarring played a role in our patient, we performed immunohistochemistry for TGF-β2, which is thought to function in the scarring of filtering blebs. Indeed, the tissue was strongly positive for this protein (Fig. 5a). Further, our sample was negative for COL1A1, which is thought to be an anti-scarring protein (Fig. 5b). These results are consistent with Sheie and colleagues’ filtering cicatrix hypothesis. The diagnosis of our patient was neoplasm-liking hyperplasia (Fig. 4), which may also support this model. However, the view of Sheie and colleagues that overhanging blebs contact only the corneal surface was not consistent with our observations. During the operation, bleeding occurred during blunt dissection of the fibrous bundles (Fig. 2d). Such a bleeding suggests that the overhanging filtering bleb had tight connections with the corneal tissue or corneoscleral limbus, rather than simply leaning on it.
In summary, the mechanism for overhanging blebs formation may be complex. The factors discussed here, such as scar hyperplasia, the action of gravity, the action of the eyelid and excessive aqueous over-filtration may interact and together contribute to the formation of overhanging filtering bleb. However, our finding that the overhanging blebs had tight connections with the corneal tissue or corneoscleral limbus, rather than simply leaning on it, might be highly related to its development and still needs to be further studied.
Natural Science Foundation of Hunan Province Project Number: 14JJ3041. National Nature Science Foundation of China Project Number: 81370913. National Nature Science Foundation of China Project Number: 81670859.
Availability of data and materials
The data supporting the conclusions of the this article is included within the article and its figures.
PB OY collected the data of the patient, performed the histological examinations of the tissue, and was a major contributor in writing the manuscript. XQ collected the data of the patient, performed the histological examinations of the tissue, and was a major contributor in writing the manuscript. XCD carried out the operation, and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent for publication of her clinical details and clinical images was obtained from the patient.
Ethics approval and consent to participate
This study has been approved by the Ethics Committee of The second Xiangya Hospital of Central South University.
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