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Drainage devices yield mixed results in eyes with post-keratoplasty glaucoma
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Glaucoma drainage devices resulted in greater IOP control, lower glaucoma surgery failure rates and lower vision loss rates than other procedures in patients with post-keratoplasty glaucoma, according to a study.
However, drainage devices were associated with higher graft failure rates than trabeculectomy and laser cyclophotocoagulation.
Ramesh S. Ayyala
“In patients with post-keratoplasty glaucoma, meta-analysis of the published data seems to favor glaucoma drainage device surgery to provide the maximum IOP reduction, highest glaucoma surgery success rate and least incidence of worsening vision. However, the incidence of graft failure is also greatest after glaucoma drainage devices compared with trabeculectomy and cyclophotocoagulation,” Ramesh S. Ayyala, MD, FRCS, FRCOphth, the corresponding author, said.
The study was published in the Journal of Glaucoma.
Methods and criteria
The study authors conducted a meta-analysis of journal articles on post-keratoplasty glaucoma published between 1970 and 2002. They selected studies in which patients with post-keratoplasty glaucoma underwent trabeculectomy, cyclophotocoagulation or implantation of glaucoma drainage devices.
Primary outcome measures were IOP control and corneal graft survival, and secondary measures were failure rates of primary glaucoma surgery and changes in visual acuity.
The authors analyzed data on 266 eyes from 13 articles, only using data from cases in which patients underwent glaucoma surgery after keratoplasty. Patients were older than 18 years and minimum follow-up was 6 months in all cases.
Results and comparisons
Sixty cases involved trabeculectomy, 111 involved cyclophotocoagulation and 95 involved placement of glaucoma drainage devices.
Average IOP reductions were 13.6 mm Hg with trabeculectomy, 20.4 mm Hg with cyclophotocoagulation and 20.2 mm Hg with drainage device. The differences between the trabeculectomy and cyclophotocoagulation groups and between the trabeculectomy and drainage device groups were statistically significant (both P < .001). The difference between the cyclophotocoagulation and drainage device groups was insignificant.
Mean glaucoma surgery failure rates were 37% after trabeculectomy, 20.7% after cyclophotocoagulation and 16% after drainage device placement; the failure rate after trabeculectomy was highest (P < .001).
Graft failure rates were 35% with drainage device placement, 21% with cyclophotocoagulation and 24% with trabeculectomy. The differences between the cyclophotocoagulation and drainage device groups (P < .001) and between the trabeculectomy and drainage device groups (P = .001) were statistically significant. The difference between the cyclophotocoagulation and trabeculectomy groups was insignificant.
Higher graft failure rates associated with glaucoma drainage device implantation may be attributed to mechanical trauma during implantation surgery and postoperative implant migration, Ayyala said.
“It is also speculated that retrograde movement of inflammatory cells through the [glaucoma drainage device] tube may increase the risk of graft failure. To overcome the potential mechanical irritation between the [glaucoma drainage device] and posterior cornea, some surgeons advocate pars plana placement of the drainage tube; however, results are variable,” he said.
Clinical evidence suggests that non-mechanical factors may also contribute to corneal decompensation, Ayyala said.
Twenty-six percent of patients in the cyclophotocoagulation group and 20% of patients in the drainage device group had postoperative worsening of vision.
“The etiology for change in vision was not clearly identified. Some studies associate it with graft decompensation. Other eyes suffered infectious keratitis, traumatic injury and retinal detachment, which contributed to visual loss,” Ayyala said.
Microincision and ab interno glaucoma surgery may be appropriate in some cases of post-keratoplasty glaucoma with open angles that are clearly visible, he said.
“If gonioscopy suggests open angles, then canal-based procedures have an excellent chance to control the IOP while potentially limiting graft failure from surgery-related trauma, given the fact that these surgeries are minimally invasive,” he said. – by Matt Hasson
Reference:
Tandon A, et al. J Glaucoma. 2014;doi:10.1097/IJG.0b013e31827a0712.For more information:
Ramesh S. Ayyala, MD, FRCS, FRCOphth, can be reached at Glaucoma Service, Department of Ophthalmology, Tulane University Medical Center, 1430 Tulane Ave. SL-69, New Orleans, LA 70112; email: rayyala@tulane.edu.Disclosure: Ayyala has no relevant financial disclosures.