Clinical Note: While highly correlated (r=0.94), VFI is less sensitive to media opacities (cataracts) than MD. This tool uses the established linear regression for HFA 24-2/30-2 analysis.
Awaiting HFA Data
Guidelines & Evidence
Clinical Details
Section 1
When to Use
Clinical Utility
Data Normalization: Converting historical or referral records that only document Mean Deviation (MD).
Patient Communication: Translating logarithmic decibel (dB) loss into an intuitive functional percentage (%).
Longitudinal Tracking: Estimating the Visual Field Index (VFI) to determine the rate of progression in chronic glaucoma.
Research Data Cleaning: Standardizing visual field metrics across heterogeneous clinical datasets.
Section 2
Formula & Logic
MD vs. VFI: The Core Difference
Metric
Scale
Sensitivity
Mean Deviation (MD)
Decibels (dB)
High sensitivity to cataracts and media opacities.
Visual Field Index (VFI)
Percentage (%)
Designed to be resistant to cataracts; focuses on neural loss.
Linear Regression Formula
VFI ≈ 100 + (3.4 × MD)
Applicable Range: 0 dB to -20 dB
Section 3
Pearls/Pitfalls
The Cataract Filter
VFI is derived from Pattern Deviation, making it a more reliable indicator of glaucomatous damage in patients with co-existing cataracts. A significant discrepancy between MD and estimated VFI suggests generalized depression (media opacity).
Section 4
Evidence Appraisal
Primary References
A visual field index (VFI) for calculation of glaucoma rate of progression
Bengtsson B et al. • Am J Ophthalmol. 2008;145(2):343-53. Original derivation of the VFI metric.
The visual field index (VFI): robustness to eye media opacities
Artes PH et al. • Ophthalmology. 2014;Large scale validation of the correlation between MD and VFI.
