Aims/Purpose: To describe a clinical case involving the obstruction of a glaucoma drainage device (GDD) caused by the presence of vitreous in the anterior chamber, a rare cause of this type of obstruction.Methods: We report the case of a 79‐year‐old patient with pseudoexfoliative secondary open‐angle glaucoma in the left eye. Despite being under hypotensive treatment with four active principles, the patient showed poor intraocular pressure (IOP) control and progression of glaucomatous damage. It was decided to implant a PreserFlo MicroShunt. During the preoperative examination, vitreous strands and capsular debris were evident in the anterior chamber, probably due to zonular dehiscence secondary to previous cataract surgery. Although the PreserFlo MicroShunt implantation and drainage bleb were performed correctly, the IOP remained elevated in the first week. Obstruction of the valvular tube by the vitreous strand was identified as the cause of GDD failure.Initially, conservative treatment with YAG laser vitreolysis was attempted but was not effective. Therefore, a new surgical intervention consisting of anterior vitrectomy, revision of the valvular tube and drainage bleb was proposed. During surgery, triamcinolone acetonide was used to stain the vitreous, as well as brilliant blue to check the patency of the valvular tube. The leakage bleb and the most distal portion of the tube were checked by conjunctival dissection and Tenon's capsule.Results: As a result of the surgical intervention, the patient was able to achieve the target IOP. Future revisions are expected to confirm stabilization of glaucomatous damage.Conclusions: In conclusion, the vitreous and capsular debris should be removed by performing a wide anterior vitrectomy prior to GDD placement if necessary. YAG laser vitreolysis may be a temporary solution, but anterior vitrectomy ensures long‐lasting patency of the drainage device.
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