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Glaucoma Drainage Device Tube Retraction and Blockage in a Patient with Iridocorneal Endothelial Syndrome Treated With Nd:YAG Membranectomy

Bonnie Nga Kwan Choy, Carol Pui Yang Chien, Jimmy Shiu Ming Lai, Jonathan Cheuk Hung Chan

Purpose: To report on a case that demonstrates the successful treatment of tube blockage of the Ahmed Glaucoma Valve at its aqueous entry site by Nd:YAG laser membranectomy. Method: We report a case of refractory intraocular pressure elevation in a patient with iridocorneal endothelial syndrome after glaucoma drainage device due to blocked tube from the iridocorneal endothelial syndrome membrane. In July 2014, our patient presented with sudden right eye elevated intraocular pressure to 67 mmHg despite a well-controlled intraocular pressure in the range of teens with timolol alone over the last 2 years. Gonioscopy showed total synechial angle closure and increasing her medical treatment failed to control the intraocular pressure. Ahmed glaucoma valve was implanted successfully. However, recurrence of raised intraocular pressure from partial tube retraction and tube blockage at its aqueous entry site by an endothelial membrane was noted at 2 weeks after the surgery. Nd:YAG laser membranectomy was performed on 2 occasions to restore the patency of the tube shunt. After the second laser membranectomy, the patient’s intraocular pressure returned to, and remained at, normal level since. Conclusion: Tube occlusion by membrane is a well-known complication following glaucoma drainage device tube in patients with iridocorneal endothelial syndrome. Nd:YAG membranectomy is effective to restore the patency of tube lumen without subjecting patients to more invasive surgical interventions including tube extender or another glaucoma drainage device. However, more studies are required to ascertain the long term effect of laser membranectomy to a blocked tube, in comparison to other treatment modalities. To our knowledge, this is the first reported case of using laser membranectomy alone in treating Ahmed glaucoma valve tube obstruction due to a retracted tube blocked by endothelial membrane.