Ahmed® Glaucoma Valve for Treatment of Refractory Glaucoma

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Author: Joseph Fong
Published:
Specialties: Ophthalmology
Schools: University of Arkansas for Medical Sciences (UAMS)
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Introduction
Intraocular pressure is the single modifiable risk factor resulting in progression of various subtypes of glaucoma. Intraocular pressure control is often achieved with topical medications, outpatient laser procedures, or minimally-invasive glaucoma surgery (MIGS). This patient is a 63-year-old with traumatic glaucoma in the right eye with elevated intraocular pressure sub-optimally controlled despite maximum medical therapy (29 mmHg). His intraocular pressure must be controlled with incisional glaucoma surgery - in this case, with placement of an Ahmed Model FP7 glaucoma valve. An advantage of valved glaucoma shunts is lower risk of postoperative hypotony-related complications compared to non-valved glaucoma shunts.

Methods
The 10 and 12 o'clock meridians are marked with a marking pen to define the borders of the conjunctival peritomy. A limbal traction 6-0 Vicryl suture is placed superotemporally in the cornea at the limbus. The conjunctival peritomy is then completed using Westcott scissors along the predetermined marks. The peritomy is extended posteriorly with blunt dissection using Stevens tenotomy scissors. Wet field cautery is used to achieve hemostasis of the scleral bed. A Stevens tenotomy hook is used to identify the superior rectus muscle and a marking pen is used to mark its border. The Ahmed Model FP7 tube shunt is then introduced onto the surgical field. Balanced salt solution is injected into the tip of the tube using a 30-gauge cannula to ensure adequate patency of the valve. The Ahmed plate is then sutured to the sclera approximately 8 mm posterior to the limbus using 5-0 Nylon suture. A corneal paracentesis is made at the 8 o'clock position, and viscoelastic is injected to deepen the anterior chamber. A 23-gauge needle attached to the Healon syringe is then used to tunnel from a point 2.0 mm posterior to the limbus into the anterior chamber. The needle tract is anterior and parallel to the plane of the iris and the surgeon must ensure that the tube does not contact the iris or corneal endothelium after insertion. The implant tube is then laid flush with the cornea and shortened with Westcott scissors with an oblique cut, bevel up. Healon is injected as the needle is withdrawn. Non-toothed forceps are then used to insert the tube into the anterior chamber. A single 8-0 Vicryl suture is used to secure the tube to the underlying sclera. A corneal patch graft is cut to fit the site of tube implantation and secured with a single 8-0 Vicryl horizontal cross mattress suture. The conjunctival peritomy is then closed with a running 8-0 Vicryl suture on a BV needle. Anchoring sutures incorporating the conjunctiva and the episclera to firmly secure the corners of the peritomy to the limbus. A 9-0 Nylon suture is used to re-approximate the limbal conjunctiva. At the conclusion of the case, the eye is returned to a neutral position, the traction suture is removed, and satisfactory intraocular pressure is confirmed by palpation.

Results
No complications arose during the procedure. Postoperatively, the patient had subconjunctival hemorrhage, injection, and mild pain that decreased over the following week. Prednisolone acetate drops were applied six times daily to prevent inflammation and moxifloxacin drops were applied four times daily to prevent infection. At the three-month follow up, the eye was quiet and intraocular pressure was measured to be 9 mmHg.

Conclusion
Implantation of an Ahmed glaucoma tube shunt is a safe procedure that can effectively treat various subtypes of glaucoma with sub-optimally controlled intraocular pressure despite maximum medical therapy.

Joseph W. Fong, MD
Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
JFong@uams.edu

Ahmed A. Sallam, MD, PhD
Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
ASallam@uams.edu

Surgery was performed at University of Arkansas for Medical Sciences, Little Rock, AR, USA.

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