Methodological quality of the review: Low confidence
Author: Tandon A, Espandar L, Cupp D, Ho S, Johnson V, Ayyala RS
Geographical coverage: Not reported
Sub-sector: Surgical management
Equity focus: Patients were 18 years or older
Review type: Effectiveness review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis method: Not applicable
Background: Penetrating keratoplasty (PKP) is a procedure often used for corneal disease, including bullous keratopathy, keratoconus and central corneal scar. Post-PKP glaucoma complications include graft decompensation, graft rejection, irregular astigmatism and glaucoma.
Post-PKP glaucoma complications are often difficult to treat medically and for which surgical intervention – either with trabeculectomy, cyclodestructive procedure or glaucoma drainage device (GDD) – is necessary. Available literatures reviewing the effect of these treatment methods are limited and it is difficult to determine which surgical approach provides the best outcome.
Objectives: To systematically review literature for the assessment of the effectiveness of trabeculectomy, cyclophotocoagulation (CPC), and GDD on intra-ocular pressure (IOP) control and corneal graft survival.
Main findings: In this study, 13 articles and 266 eyes were included. Findings indicated that trabeculectomy (Trab) reduced IOP by 13.6 mm Hg compared with 20.4 mm Hg with CPC and 20.2 mm Hg with GDD (P<0.001). The failure rate of glaucoma surgery was highest after Trab 37% (95% CI, 31.4%-41.9%) compared with 20.7% (95% CI, 17.6%-23.7%) after CPC and 16% (95% CI, 13.8%-18.9%) after GDD (P<0.001).
GDD was associated with higher rate of corneal graft failure (35%) than either CPC or Trab (21% and 24%, P=0.001 and P<0.001, respectively). The percentage of patients who experienced worsening of vision was the highest after CPC (26%) and the least with GDD (20%). Based on these findings, authors concluded that compared with other forms of glaucoma surgery, GDD is associated with greater IOP control, the lowest glaucoma surgery failure rate, and less vision loss in patients with postkeratoplasty glaucoma. However, GDD surgery is also associated with higher rate of graft failure.
Methodology: Medline (Ovid, PubMed), EMBASE, and The Cochrane Library databases for clinical articles were searched for articles published between January 1 1970 to January 1 2012. The primary outcome measures were IOP control and overall corneal graft survival. The secondary outcomes were failure rate of the primary glaucoma procedure and change in visual acuity. One-way analysis of variance weighed by the number of participants in each study was used to compare the outcomes. Two reviewers independently performed data extraction and quality assessment of the studies that maintained the inclusion criteria.
Applicability/external validity: The applicability/external validity were not discussed.
Geographic focus: This review was focused on all countries but it is not clear if studies from low/middle-income countries were found/included or not.
Summary of quality assessment: This study was awarded low confidence in the conclusions about the effects of this review. Although authors searched relevant databases, reference lists of the included studies were not searched and authors/experts were not contacted for additional information. The language bias could not be verified. In addition, the criteria for assessing quality of included studies were not clear and heterogeneity was not addressed.