What is the role of surgery 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

Uncontrolled IOP after PKP can result in graft failure and vision loss. Intraocular pressure should be monitored regularly after corneal transplantation, and uncontrolled IOP should be treated aggressively. Any patient with preexisting glaucoma must be carefully evaluated before a corneal transplant. Medical management is the first-line treatment, and newly developed drugs are constantly in production.

Patients with uncontrolled IOP or patients with borderline control with 2 or more medications may be treated with either trabeculectomy or GDD surgery before or at the same time as the planned corneal transplant. This recommendation is based on results of multiple studies demonstrating that preoperative glaucoma puts patients at high risk for the development of PKPG and graft failure. [9, 13, 14, 15, 16, 17, 18, 82]  Penetrating keratoplasty and glaucoma unresponsive to medications should be treated surgically. First-time trabeculectomy is the safest operation in terms of both IOP control and graft survival.

The literature favors a combined trabeculectomy with a corneal graft procedure in patients with preexisting glaucoma who need a corneal transplant. [41, 63, 64, 66, 67, 68]  Additional surgical procedures should be avoided, if possible, at the time of the trabeculectomy because they are associated with a higher incidence of trabeculectomy failure. [64]

Glaucoma drainage device surgery is preferred over other surgical options for patients with PKPG who have extensive limbal conjunctival scarring, shallow anterior chambers, or extensive peripheral anterior synechiae and for those in whom trabeculectomy has failed. Glaucoma drainage device surgery appears to be superior to cyclodestructive procedures for patients in whom trabeculectomy has failed or for patients in whom trabeculectomy is contraindicated (ie, individuals who wear contact lenses), but this is still debated.

Akdemir and colleagues [83]  found significant differences in results after trabeculectomy compared with Ahmed glaucoma valve implantation in patients who previously underwent PKP. This study showed a greater mean loss of endothelial cell counts with Ahmed glaucoma valve implantation compared with trabeculectomy but greater decrease in IOP (64.2% vs 46.9%) at 12-month follow-up in the Ahmed valve group. 

A comparison study by Yakin and colleagues [84]  (n = 84) also demonstrated better IOP control with use of a GDD versus trabeculectomy with and without antimetabolites, but with lower graft survival rates by about 8% to 15% in the GDD group. Nassiri and colleagues [85]  showed no significant difference in any outcome measure between trabeculectomy and Ahmed valve implantation in patients for whom previous filtering surgeries failed. This discrepancy over various studies highlights that although GDD surgery is preferred in more complicated cases, more studies are needed to deduce its true advantage over other surgical options for patients with PKPG.

Glaucoma drainage device surgery also has advantages over cyclodestructive procedures. Although GDD surgery and cyclodestructive procedures appear to be the same in terms of graft failure, there appears to be a higher incidence of permanent vision loss and hypotony after cyclodestructive procedures. [77]

It is vital to lower IOP and control PKPG because although a graft can usually be repeated, if the optic nerve is damaged from end-stage glaucoma, useful vision cannot be restored.


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