Evaluating High Intraocular Pressure Criteria for Failure in Glaucoma Surgery: Impact on Estimated Success and Visual Field Rates.

Purpose

Review high intraocular pressure (IOP) thresholds used as failure criteria in glaucoma surgical outcome studies, evaluate their impact on success rates, and examine the relationship between surgical success criteria and visual field (VF) progression rates.

Design

Systematic literature review and application of high IOP failure criteria to 2 retrospective cohorts.

Participants

Two cohorts of 934 and 1765 eyes underwent trabeculectomy and deep sclerectomy (DS), respectively, with a median follow-up of 41.4 months for trabeculectomy and 45.4 months for DS. Visual field analysis was conducted on patients in the trabeculectomy cohort with ≥4 VFs in ≥2 years post-surgery.

Methods

We applied literature-based high IOP failure criteria to the patient cohorts, defining failure as exceeding these IOP thresholds, loss of light perception, hypotony revision surgery, or need for additional IOP-lowering surgery. Success rates were estimated with Kaplan-Meier statistics, and Cohen's kappa statistic assessed the agreement among criteria in defining failure at 5 years. Linear mixed models estimated VF mean deviation (MD) progression rates based on success or failure status.

Main outcome measures

Kaplan-Meier success rates, Cohen's kappa, and MD progression rates.

Results

From 2503 initial studies, 277 were included, identifying 144 high IOP failure criteria. The 21-mmHg criterion variations showed success rates at 5 years ranging from 8.7% to 74.0% for trabeculectomy and 22.1% to 89.9% for DS. The median Cohen's kappa for 21-mmHg criteria indicated fair agreement (0.39 for trabeculectomy, 0.42 for DS). A subset of 339 trabeculectomy eyes were eligible for the VF analysis. Overall, the median (interquartile range) postoperative progression rate was -0.36 (-0.09 to -0.74) dB/year. Distributions of progression rates greatly overlapped between failure and success groups as defined by the various criteria.

Conclusions

The criteria for defining high IOP failure in glaucoma surgery are highly heterogeneous in the current literature. Varying high IOP criteria has a large impact on glaucoma surgery success rates, highlighting the need for standardized failure criteria to enable consistent interpretation and comparison across studies. IOP-based classifications are poor surrogates for postoperative VF progression rates. Long-term visual field rates provide a more consistent primary outcome measure and may be incorporated into composite success criteria.