Glaucoma Drainage Implant Surgery | PristynCare

Risk Factors

Good candidates for glaucoma drainage implant surgery include:

• Patients with refractory glaucoma not controlled by two or more medications
• Those who have failed trabeculectomy or where bleb formation is unlikely
• Patients with active ocular inflammation (uveitic glaucoma)
• Eyes with extensive conjunctival scarring preventing standard filtration surgery
• Patients with neovascular glaucoma after pan-retinal photocoagulation

Who Needs This Surgery

Before surgery, comprehensive glaucoma evaluation including visual field testing, optic disc photography, OCT of the retinal nerve fiber layer, gonioscopy, and maximum medical IOP control is performed. Consent and discussion of realistic expectations are important, as drainage implants control IOP but do not recover lost vision.

Diagnosis

Pre-operative assessment for glaucoma drainage implant includes:

• IOP measurement with Goldmann applanation tonometry
• Gonioscopy to assess the anterior chamber angle
• Optic disc evaluation with fundus photography and OCT RNFL
• Visual field testing (Humphrey 24-2 or 30-2) to document baseline function
• Corneal endothelial cell count to assess risk from the tube
• Ultrasonography (B-scan) if the fundus is not visible

Treatment Plan

Pre-operatively, IOP is reduced as much as possible with maximum tolerated medications. Trabeculectomy revision or MIGS may be considered first in appropriate cases. If these are not suitable, a glaucoma drainage implant is planned. Post-operatively, the tube position and IOP are monitored at each visit and topical medications are adjusted as the drainage bleb matures.

Tube Shunt Surgery Steps

Glaucoma drainage implant surgery involves the following steps:

• Anesthesia: local with monitored sedation or general anesthesia
• A conjunctival peritomy is made in the chosen quadrant (usually superotemporal)
• The plate of the implant is sutured to the sclera 8 to 10 mm posterior to the limbus
• For non-valved implants, the tube is temporarily ligated to prevent hypotony during the bleb maturation phase
• A donor corneal or pericardial patch graft is placed over the tube near the limbus to prevent erosion
• The tube is inserted into the anterior chamber through a limbal incision
• Conjunctiva is closed over the device
• Post-operative topical antibiotics and steroids are started
• IOP is monitored closely in the immediate post-operative period

Recovery After Surgery

Post-operative care after glaucoma tube shunt surgery includes:

• Instill topical steroid and antibiotic drops as prescribed
• Avoid bending forward or lifting heavy objects for 2 to 4 weeks
• Wear an eye shield during sleep for 4 weeks
• Do not swim or submerge the face for 6 weeks
• Attend follow-up visits at 1 day, 1 week, 2 weeks, 1 month, and 3 months post-operatively
• Continue glaucoma drops until the tube becomes functional (usually 6 to 8 weeks for non-valved implants)

Risks and Complications of Tube Shunt Surgery

Possible complications of glaucoma drainage implant surgery include:

• Hypotony: Excessively low IOP causing vision disturbance in the early post-operative period
• Tube occlusion: Blockage of the silicone tube by vitreous, blood, or fibrous tissue
• Corneal decompensation: Endothelial cell loss from the tube touching the cornea
• Diplopia: Double vision from restriction of extraocular muscles by the plate
• Tube erosion: Exposure of the tube through the conjunctiva or patch graft
• Encapsulated bleb: Fibrosis around the plate causing IOP to rise after initial control
• Endophthalmitis: Rare but serious risk of intraocular infection