What is the role of trabeculectomy in the treatment of penetrating keratoplasty and glaucoma (PKPG)?

Updated: Dec 30, 2020
  • Author: Shibandri Das, MD; Chief Editor: Inci Irak Dersu, MD, MPH  more...
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Answer

Rates of trabeculectomy success in treating PKPG are highly variable. [56, 57]  Conventional trabeculectomy without antimetabolites (5-fluorouracil [5-FU]) and alkylating agents (mitomycin-C) in patients with PKPG has a high failure rate secondary to limbal conjunctival scarring from previous surgery, extensive peripheral synechiae, aphakia, and extremely shallow anterior chambers. [56]

The introduction of 5-FU and mitomycin-C has increased the success rate of trabeculectomies, especially in patients with complicated glaucoma. [58]  These agents appear to increase the success rate by inhibiting fibroblast proliferation and enhancing the formation of filtering blebs. Apart from the inconvenience of frequent injections, administration of 5-FU is associated with a high rate of corneal epithelial toxicity, corneal ulceration, corneal perforation, and stem cell failure, which could prove to be disastrous to the graft. [59]  Use of 5-FU should be avoided in patients with a damaged epithelium and persistent epithelial defects. Because of corneal toxicity, 5-FU should be used with caution in patients with PKPG.

Intraoperative local application of mitomycin-C has significantly improved the success rate of filtering surgery for glaucoma. [60]  

In addition to the convenience of a single application at the time of surgery, mitomycin-C trabeculectomy has no demonstrable toxicity on the corneal epithelium; however, mitomycin-C trabeculectomy may result in thin cystic bleb formation and an increased risk of bleb-related infection. [61]  The reported success rate in IOP control with mitomycin-C trabeculectomy in patients with PKPG is 67 to 91%, and the rate of graft failure is 12 to 18%. [62, 63]  The bleb failure rate is higher when trabeculectomy is combined with additional surgical procedures, such as cataract surgery and vitrectomy. [64]

Trabeculectomy with mitomycin-C can be attempted in patients with limited or no superior limbal conjunctival scarring, no extensive peripheral anterior synechiae, no aphakia, and extremely shallow anterior chambers. Avoid this procedure in patients who use contact lenses because it can predispose them to bleb infection. Avoid shallow or flat anterior chambers in the postoperative period because this could compromise the graft endothelium.

Patients who have undergone trabeculectomy should be monitored for dellen formation, which can trigger thinning of the adjacent graft cornea, leaking blebs, and bleb-related infections.


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