Dissecting Trabeculectomy Filtering Bleb Masquerading as Ocular Surface Squamous Neoplasia

A 79-year-old woman with a history of glaucoma and bilateral trabeculectomies presented with a large conjunctival mass concerning for ocular surface squamous neoplasia. Examination revealed a large, keratinized, vascularized lesion overlying the superior bulbar conjunctiva and cornea. Ultrasound biomicroscopy demonstrated a well-defined, encapsulated mass. The lesion was excised with amniotic membrane graft placement. Histopathology revealed findings consistent with a failed glaucoma filtering bleb, including keratinized stratified squamous epithelium, subepithelial edema, fibrovascular tissue, and dense collagen. No evidence of dysplasia or malignancy was found. Postoperatively, visual acuity improved to 20/20 with a well-formed bleb and controlled intraocular pressure. This case illustrates an unusual presentation of a failed filtering bleb mimicking ocular surface neoplasia and highlights the importance of histopathologic evaluation in differentiating benign postoperative changes from malignancy. Clinicians should consider filtering bleb complications in the differential diagnosis of conjunctival masses in patients with prior glaucoma surgery.