Evaluating the accuracy of the visual field index for the Humphrey Visual Field Analyzer in patients with mild to moderate glaucoma

Abstract

Purpose: To evaluate the accuracy of the visual field index (VFI) for the Humphrey Visual Field Analyzer in a population of patients with mild to moderate glaucoma.

Design: Retrospective cohort study.

Methods: The study included 42 patients (61 eyes) with at least 11 years of follow-up, and annual automated visual fields (VFs). Patients with mean deviations ≤-20 dB were excluded. All unreliable fields were omitted (fixation losses ≥20%, false-positive ≥15%, false-negative ≥33%). The VFs were divided into two 5-year series and the data were analyzed by the new Humphrey Visual Field Analyzer software. Projected VFIs from the first 5 years were compared with observed values obtained from the last 5 years. Unreliable fields initially excluded were reintroduced into the series (22 eyes) to create a comparison.

Results: Predicted VFIs were accurate with a mean overestimation of VF deterioration of 1.37% (95% CI: -0.22%, 2.96%). Of the predicted values, 95% were between -4.5% and 5.2% of the observed values when the predicted VFI was ≥90%; and between -13.8% and 20.5% when the predicted VFI was <90%. No statistical difference was found between the reliable and unreliable series (mean difference of 0.09% [95% CI: -0.41%, 0.59%]).

Conclusion: The new software for the Humphrey Visual Field Analyzer projects an accurate value for patients when the predicted VFI is ≥90%. Clinicians should consider the limitations of the software, especially for those patients with greater initial VF loss.