Glaucoma drainage implants (GDIs) are usually indicated for the treatment of eyes with glaucoma uncontrolled by topical and oral medications. Pars plana GDIs are considered in specific cases where there is a risk of complications associated with the insertion of GDIs in the anterior chamber (AC). These indications may include eyes with very narrow AC, failure of GDI placed in the AC, pre-existing corneal disease, or angle neovascularization.1,2 This approach decreases the rate of perioperative and postoperative complications related to GDI insertion (including hyphema). Complete removal of the vitreous at the site of GDIs implantation is important to reduce secondary tube occlusion and subsequent intraocular pressure increase.3,4
The aim of this report is to describe a new surgical technique to induce anterior hyaloid detachment in eyes that will undergo pars plana GDI insertion or in eyes with blocked pars plana GDI.
The vitrectomy is done through the pars plana in the classic way. If absent, the posterior vitreous detachment is induced, and residual peripheral vitreous is removed using wide-angle non-contact lens assisted with scleral indentation. The next step in this procedure is inducing anterior hyaloid detachment at the anterior vitreous base: a 26-gauge or 27-gauge needle connected to a 3-mL syringe filled with filtered air is introduced 3 mm from the limbus at the nasal or temporal side (Figure a). The needle is introduced in the sclera; then under 23-gauge endoscopic visualization (introduced through a 23-gauge trocar, or through a corneal incision in aphakic patients), we assure that the tip of the needle has completely passed across the full thickness of the sclera and ciliary body at the pars plana. We introduce the needle a little further to see a tent-like appearance in front of the needle indicating that it is just underneath the anterior hyaloid but did not perforate it (Figure a). Then, 0.5 mL to 1 mL of filtered air is injected smoothly to induce anterior hyaloid separation. A doughnut-like appearance of the air trapped anterior to the anterior hyaloid confirms the separation (Figure b). Under 23-gauge endoscopic visualization, the vitrector is used to cut and remove anterior vitreous and hyaloid (Figure c). We recommend starting cutting at the meridian corresponding to tube insertion to ensure complete shaving at this site. The surgical technique is documented in a video, which represents key steps for the described surgical technique (Supplemental Video coming soon).
Key steps in the surgical technique: (a) The 26-gauge needle connected to a syringe filled with filtered air is introduced at the pars plana. A tent-like appearance in front of the needle indicates that it passed through sclera and pars plana, and is just underneath the anterior hyaloid. (b) A doughnut-like appearance of the air trapped anterior to the anterior hyaloid confirms anterior hyaloid detachment. (c) A vitrector is used to safely cut and remove anterior vitreous and hyaloid.
The GDI is implanted in the superotemporal quadrant in the usual fashion, and the superotemporal sclerotomy is used for GDI placement. All sclerotomies (except for the superotemporal one in case of GDI implantation) are closed using 7-0 Vicryl suture.
We have used this technique in two cases: The first patient had Ahmed valve (New World Medical, Rancho Cucamonga, CA) blockage by the anterior vitreous hyaloid in his left aphakic eye, and the second patient had neovascular glaucoma secondary to proliferative diabetic retinopathy. The intraocular pressure (IOP) decreased in both patients postoperatively, and the tube remained permeable in both eyes during the follow-up period (12 and 16 months, respectively).
The above-described technique is the approach we used for the two reported cases. Some modifications can be done depending on the surgeon's preferences (viewing system [contact or non-contact], type of GDI, quadrant used for insertion, and type of used sutures).
Tube occlusion after combined pars plana vitrectomy and GDI implantation can occur in up to 10% of eyes. It is mainly related to entrapment of residual anterior vitreous gel in the implant. Patients may require a second intervention for tube revision to ensure IOP control.4
Many strategies have been reported to prevent this possible complication. Luttrull et al.1 used gas-fluid exchange and perfluoropropane gas tamponade (“pneumatic stent”) to regulate the IOP in the early postoperative period and minimize postoperative hypotony and pressure spikes. The intraocular gas bubble allows displacement of residual vitreous away from the implanted GDI and prevents possible obstruction. This technique is useful in the early postoperative period but may not prevent delayed obstruction. Wallsh et al. proposed the use of intravitreal triamcinolone acetonide to assure better visualization of the vitreous during the vitrectomy.5 They also advocated using a beveled incision and a beveled tube opening to reduce the rate of tube occlusion.5
Our described technique could be combined with both strategies and can increase the likelihood of achieving a complete removal of anterior vitreous gel.
This technique requires that the retina surgeon be familiar with small-gauge endoscopic vitrectomy techniques, and a learning curve is needed to ensure the success of the technique. Care should be taken to inject the air into the sub-anterior hyaloid space and not anterior to the nonpigmented epithelium or suprachoroidal space. Larger comparative series with long-term follow-up are needed to confirm the results of our described surgical technique and to compare its success and complication rates to other techniques.
- Luttrull JK, Avery RL, Baerveldt G, Easley KA. Initial experience with pneumatically stented baerveldt implant modified for pars plana insertion for complicated glaucoma. Ophthalmology. 2000;107(1):143–149. doi:10.1016/S0161-6420(99)00034-2 [CrossRef]
- Scott IU, Alexandrakis G, Flynn HW Jr., et al. Combined pars plana vitrectomy and glaucoma drainage implant placement for refractory glaucoma. Am J Ophthalmol. 2000;129(3):334–341. doi:10.1016/S0002-9394(99)00363-3 [CrossRef]
- Desatnik HR, Foster RE, Rockwood EJ, Baerveldt G, Meyers SM, Lewis H. Management of glaucoma implants occluded by vitreous incarceration. J Glaucoma. 2000;9(4):311–316. doi:10.1097/00061198-200008000-00005 [CrossRef]
- Kolomeyer AM, Seery CW, Emami-Naeimi P, Zarbin MA, Fechtner RD, Bhagat N. Combined pars plana vitrectomy and pars plana baerveldt tube placement in eyes with neovascular glaucoma. Retina. 2015;35(1):17–28. doi:10.1097/IAE.0000000000000235 [CrossRef]
- Wallsh JO, Gallemore RP, Taban M, Hu C, Sharareh B. Pars plana ahmed valve and vitrectomy in patients with glaucoma associated with posterior segment disease. Retina. 2013;33(10):2059–2068. doi:10.1097/IAE.0b013e31828992c3 [CrossRef]