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Histopathology in a dissecting conjunctival filtering bleb
Histopathology in a dissecting conjunctival filtering bleb Michael D. O’Connor,* MD, FRCSC; Renée Talbot,* MD; Seymour Brownstein,*† MD, FRCSC; Nigel Rawlings,*† MD; Karim F. Damji,* MD, MBA, FRCSC ABSTRACT • RÉSUMÉ
Case report: Four years after trabeculectomy, a patient developed unilateral tearing and presented with an ipsilateral conjunctival filtering bleb that had dissected into the cornea.The corneal portion of the bleb was excised for symptomatic relief. Histopathological examination disclosed dissection of the conjunctival filtering bleb into the cornea between Bowman’s layer and the corneal epithelium. The internal portion of the bleb consisted of loose stromal tissue lacking any internal epithelial lining. Comments: A conjunctival bleb dissecting into the cornea is a well-described late complication of trabeculectomy; however, its pathophysiology remains controversial. The subepithelial dissection plane in this specimen supports the concept that the conjunctival filtering bleb may dissect into, as well as “overhang”, the limbal cornea. Observations : Quatre ans après une trabéculectomie, un patient avec larmoiement unilatéral postopératoire s’est présenté avec une section de la bulle de filtration conjonctivale homolatérale dans la cornée. La partie cornéenne de la bulle a été excisée, entraînant un soulagement symptomatique. L’examen histopathologique a révélé que la section de la bulle de filtration conjonctivale dans la cornée se trouvait entre la membrane de Bowman et l’épithélium cornéen. La portion interne de la bulle était faite de tissus lâches du stroma, sans l’épithélium interne. Commentaires : La dissection de la bulle conjonctivale dans la cornée est une des complications tardives bien décrite de la trabéculectomie; toutefois, sa pathophysiologie prête toujours à controverse. Le plan de dissection sous-épithélial de ce spécimen étaye l’hypothèse voulant que la bulle de filtration conjonctivale puisse se disséquer dans le limbe cornéen, ou même le « surplomber ».
D
issecting bleb is a late complication of trabeculectomy. In this condition, the conjunctival filtering bleb expands from its limbal limit, migrating over or within the cornea. Associated symptoms and signs include foreign body sensation, tearing, lagophthalmos, dellen, as well as decreased visual acuity secondary to bleb-induced astigmatism and bleb expansion.1–6 Surgical excision of the corneal portion of the bleb offers definitive management,1–5 although laser treatment has been proposed as an alternative in select cases.6 The term “dissecting bleb” suggests that the filtering bleb actually dissects through the superficial cornea, but the pathophysiology of this entity is controversial.1–5 Some authors have suggested that the conjunctival bleb, also called an overhanging bleb, expands to drape over the corneal epithelium.1
We report the histopathological findings in a dissecting bleb that was surgically resected for symptomatic relief of tearing. CASE
REPORT
A 77-year-old woman underwent uncomplicated combined cataract surgery and fornix-based trabeculectomy with mitomycin C. Four years later, she presented with a 2-month history of unilateral tearing. Examination revealed a thin-walled, avascular bleb that involved the superior cornea extending into the pupillary margin (Fig. 1).
From *the University of Ottawa Eye Institute and †the Department of Pathology, the Ottawa Hospital, Ottawa, Ont. Originally received Feb. 4, 2007 Accepted for publication Sep. 21, 2007 Published online Jan. 18, 2008 Correspondence to: Michael D. O’Connor, MD, University of Ottawa Eye Institute, the Ottawa Hospital – General Campus, 501 Smyth Road, Rm. W6287, Box 307, Ottawa, ON K1H 8L6; [email protected] This article has been peer-reviewed. Cet article a été évalué par les pairs. Can J Ophthalmol 2008;43:114–5 doi:10.3129/i07-209
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Fig. 1—Intraoperative photograph demonstrating initial blunt dissection of dissecting bleb located at the superior cornea.
Dissecting bleb histopathology—O’Connor et al. Uncomplicated bleb revision surgery was undertaken. The corneal portion of the bleb was bluntly dissected and then excised at the limbus (Fig. 2). No sutures were required. The submitted specimen consisted of the bleb and the superior superficial cornea (Fig. 3). Histopathological examination disclosed loose connective tissue elements between the limbal corneal epithelium and Bowman’s layer, consistent with a subepithelial bleb dissection plane (Fig. 4). The loose connective tissue elements that formed the inner portion of the bleb were not associated with any internal epithelial bleb lining. The tearing was no longer a problem during 18 months of postoperative follow-up.
Fig. 2—Intraoperative photograph demonstrating limbal excision of dissecting bleb.
Fig. 3—Excised bleb is lined by epithelium with adjacent corneal portions of peripheral Bowman’s layer (arrows) and loose stromal elements (hematoxylin and eosin, original magnification ×50). Note that the specimen is a single epithelial sheet folded over itself, rather than an enclosed cyst.
Fig. 4—At the margin of the bleb, the plane of the bleb dissection (arrow) is identified between corneal epithelium and Bowman’s layer. Loose connective tissue is identified in the subepithelial portion of the bleb (periodic acid-Schiff, original magnification ×200).
COMMENTS
Management of dissecting blebs is generally directed by symptomatology and initially involves lubrication, followed by surgical excision if warranted. In our experience, the corneal portion of the bleb is commonly loculated and thus compartmentalized from the original conjunctival portion, which continues to function normally. Consequently, the corneal portion of the bleb may be managed with blunt dissection from the cornea followed by limbal excision.1–5 As illustrated in our case, this can often be performed without leakage or the need for suturing. A sutureless technique has also been advocated by Anis et al.,5 who reported 6 cases of sutureless bleb revision, only 1 of these cases subsequently requiring suturing for a persistent bleb leak. The simplicity of surgical dissection and removal of the dissecting bleb may suggest that the conjunctival bleb lies on rather than within the cornea.1 In contrast, some authors have proposed that the dissecting portion of the bleb lies under the corneal epithelium.2,4 Anis et al. have stated that the bleb lies on the surface of Bowman’s layer.5 The evidence for this assertion, however, has been weakened by the fact that Bowman’s layer was not identified histopathologically in previous studies.2,4 In contrast, the present case provides evidence in support of a dissection plane overlying Bowman’s membrane. We identified Bowman’s layer at the corneal margin of the bleb, thus localizing the bleb within the corneal subepithelial space. In summary, dissecting blebs are an uncommon complication of trabeculectomy and, if symptomatic, they may be managed with limited excision of the corneal component of the bleb. The histopathological findings in this case suggest a subepithelial dissection component of the bleb into the cornea. The precise dissection plane may vary among cases, and further histopathological investigations are warranted in this regard. REFERENCES 1. Scheie HG, Guehl JJ. Surgical management of overhanging blebs after filtering procedures. Arch Ophthalmol 1979;97:325–6. 2. Ulrich GG, Proia AD, Shields MB. Clinicopathologic features and surgical management of dissecting glaucoma filtering blebs. Ophthalmic Surg Lasers 1997;28:151–5. 3. Mandal AK, Vemuganti GK, Ladda N, Veenashree MP. Partial excision with a conjunctival advancement flap after a relaxing incision for a dissecting glaucoma filtering bleb. Ophthalmic Surg Lasers 2002;33:497–500. 4. Grostern RJ, Torczynski E, Brown SVL. Surgical repair and histopathologic features of a dissecting glaucoma filtration bleb. Arch Ophthalmol 1999;117:1566–7. 5. Anis S, Ritch R, Shihadeh W, Liebmann J. Sutureless revision of overhanging filtering blebs. Arch Ophthalmol 2006;124:1317–20. 6. Sony P, Kumar H, Pushker N. Treatment of overhanging blebs with frequency-doubled Nd:YAG laser. Ophthalmic Surg Laser Imaging 2004;35:429–32. Key words: conjunctival filtering bleb, dissecting bleb, overhanging bleb, bleb dysesthesia, trabeculectomy complications CAN J OPHTHALMOL—VOL. 43, NO. 1, 2008
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Case report: Four years after trabeculectomy, a patient developed unilateral tearing and presented with an ipsilateral conjunctival filtering bleb that had dissected into the cornea.The corneal portion of the bleb was excised for symptomatic relief. Histopathological examination disclosed dissection of the conjunctival filtering bleb into the cornea between Bowman’s layer and the corneal epithelium. The internal portion of the bleb consisted of loose stromal tissue lacking any internal epithelial lining. Comments: A conjunctival bleb dissecting into the cornea is a well-described late complication of trabeculectomy; however, its pathophysiology remains controversial. The subepithelial dissection plane in this specimen supports the concept that the conjunctival filtering bleb may dissect into, as well as “overhang”, the limbal cornea. Observations : Quatre ans après une trabéculectomie, un patient avec larmoiement unilatéral postopératoire s’est présenté avec une section de la bulle de filtration conjonctivale homolatérale dans la cornée. La partie cornéenne de la bulle a été excisée, entraînant un soulagement symptomatique. L’examen histopathologique a révélé que la section de la bulle de filtration conjonctivale dans la cornée se trouvait entre la membrane de Bowman et l’épithélium cornéen. La portion interne de la bulle était faite de tissus lâches du stroma, sans l’épithélium interne. Commentaires : La dissection de la bulle conjonctivale dans la cornée est une des complications tardives bien décrite de la trabéculectomie; toutefois, sa pathophysiologie prête toujours à controverse. Le plan de dissection sous-épithélial de ce spécimen étaye l’hypothèse voulant que la bulle de filtration conjonctivale puisse se disséquer dans le limbe cornéen, ou même le « surplomber ».
D
issecting bleb is a late complication of trabeculectomy. In this condition, the conjunctival filtering bleb expands from its limbal limit, migrating over or within the cornea. Associated symptoms and signs include foreign body sensation, tearing, lagophthalmos, dellen, as well as decreased visual acuity secondary to bleb-induced astigmatism and bleb expansion.1–6 Surgical excision of the corneal portion of the bleb offers definitive management,1–5 although laser treatment has been proposed as an alternative in select cases.6 The term “dissecting bleb” suggests that the filtering bleb actually dissects through the superficial cornea, but the pathophysiology of this entity is controversial.1–5 Some authors have suggested that the conjunctival bleb, also called an overhanging bleb, expands to drape over the corneal epithelium.1
We report the histopathological findings in a dissecting bleb that was surgically resected for symptomatic relief of tearing. CASE
REPORT
A 77-year-old woman underwent uncomplicated combined cataract surgery and fornix-based trabeculectomy with mitomycin C. Four years later, she presented with a 2-month history of unilateral tearing. Examination revealed a thin-walled, avascular bleb that involved the superior cornea extending into the pupillary margin (Fig. 1).
From *the University of Ottawa Eye Institute and †the Department of Pathology, the Ottawa Hospital, Ottawa, Ont. Originally received Feb. 4, 2007 Accepted for publication Sep. 21, 2007 Published online Jan. 18, 2008 Correspondence to: Michael D. O’Connor, MD, University of Ottawa Eye Institute, the Ottawa Hospital – General Campus, 501 Smyth Road, Rm. W6287, Box 307, Ottawa, ON K1H 8L6; [email protected] This article has been peer-reviewed. Cet article a été évalué par les pairs. Can J Ophthalmol 2008;43:114–5 doi:10.3129/i07-209
114
CAN J OPHTHALMOL—VOL. 43, NO. 1, 2008
Fig. 1—Intraoperative photograph demonstrating initial blunt dissection of dissecting bleb located at the superior cornea.
Dissecting bleb histopathology—O’Connor et al. Uncomplicated bleb revision surgery was undertaken. The corneal portion of the bleb was bluntly dissected and then excised at the limbus (Fig. 2). No sutures were required. The submitted specimen consisted of the bleb and the superior superficial cornea (Fig. 3). Histopathological examination disclosed loose connective tissue elements between the limbal corneal epithelium and Bowman’s layer, consistent with a subepithelial bleb dissection plane (Fig. 4). The loose connective tissue elements that formed the inner portion of the bleb were not associated with any internal epithelial bleb lining. The tearing was no longer a problem during 18 months of postoperative follow-up.
Fig. 2—Intraoperative photograph demonstrating limbal excision of dissecting bleb.
Fig. 3—Excised bleb is lined by epithelium with adjacent corneal portions of peripheral Bowman’s layer (arrows) and loose stromal elements (hematoxylin and eosin, original magnification ×50). Note that the specimen is a single epithelial sheet folded over itself, rather than an enclosed cyst.
Fig. 4—At the margin of the bleb, the plane of the bleb dissection (arrow) is identified between corneal epithelium and Bowman’s layer. Loose connective tissue is identified in the subepithelial portion of the bleb (periodic acid-Schiff, original magnification ×200).
COMMENTS
Management of dissecting blebs is generally directed by symptomatology and initially involves lubrication, followed by surgical excision if warranted. In our experience, the corneal portion of the bleb is commonly loculated and thus compartmentalized from the original conjunctival portion, which continues to function normally. Consequently, the corneal portion of the bleb may be managed with blunt dissection from the cornea followed by limbal excision.1–5 As illustrated in our case, this can often be performed without leakage or the need for suturing. A sutureless technique has also been advocated by Anis et al.,5 who reported 6 cases of sutureless bleb revision, only 1 of these cases subsequently requiring suturing for a persistent bleb leak. The simplicity of surgical dissection and removal of the dissecting bleb may suggest that the conjunctival bleb lies on rather than within the cornea.1 In contrast, some authors have proposed that the dissecting portion of the bleb lies under the corneal epithelium.2,4 Anis et al. have stated that the bleb lies on the surface of Bowman’s layer.5 The evidence for this assertion, however, has been weakened by the fact that Bowman’s layer was not identified histopathologically in previous studies.2,4 In contrast, the present case provides evidence in support of a dissection plane overlying Bowman’s membrane. We identified Bowman’s layer at the corneal margin of the bleb, thus localizing the bleb within the corneal subepithelial space. In summary, dissecting blebs are an uncommon complication of trabeculectomy and, if symptomatic, they may be managed with limited excision of the corneal component of the bleb. The histopathological findings in this case suggest a subepithelial dissection component of the bleb into the cornea. The precise dissection plane may vary among cases, and further histopathological investigations are warranted in this regard. REFERENCES 1. Scheie HG, Guehl JJ. Surgical management of overhanging blebs after filtering procedures. Arch Ophthalmol 1979;97:325–6. 2. Ulrich GG, Proia AD, Shields MB. Clinicopathologic features and surgical management of dissecting glaucoma filtering blebs. Ophthalmic Surg Lasers 1997;28:151–5. 3. Mandal AK, Vemuganti GK, Ladda N, Veenashree MP. Partial excision with a conjunctival advancement flap after a relaxing incision for a dissecting glaucoma filtering bleb. Ophthalmic Surg Lasers 2002;33:497–500. 4. Grostern RJ, Torczynski E, Brown SVL. Surgical repair and histopathologic features of a dissecting glaucoma filtration bleb. Arch Ophthalmol 1999;117:1566–7. 5. Anis S, Ritch R, Shihadeh W, Liebmann J. Sutureless revision of overhanging filtering blebs. Arch Ophthalmol 2006;124:1317–20. 6. Sony P, Kumar H, Pushker N. Treatment of overhanging blebs with frequency-doubled Nd:YAG laser. Ophthalmic Surg Laser Imaging 2004;35:429–32. Key words: conjunctival filtering bleb, dissecting bleb, overhanging bleb, bleb dysesthesia, trabeculectomy complications CAN J OPHTHALMOL—VOL. 43, NO. 1, 2008
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