7. Serial Visual Field Analysis

Serial Visual Field Analysis

  • Visual field tests are inherently variable due to patient factors such as distraction and inattentiveness.

  • There is high disagreement about whether a patient’s visual field loss is progressing, especially in glaucoma.

  • Computer-assisted analysis programs have been developed to improve assessment of progression by correcting the “noise” and data variability.

  • Trend-based analysis techniques assess the rate of change in the visual field over time.

  • For most progression analyses, a minimum of four to five field tests in a series is required to identify progression; more tests are needed for reliable trend-based analysis.

Glaucoma Progression Analysis (GPA)

  • GPA is implemented on the Humphrey Field Analyzer (HFA).

  • Uses pattern deviation plots from SITA Standard or SITA Fast to correct for developing cataracts and pupil effects.

  • GPA identifies significant pointwise progression based on statistical probabilities using at least 3 sequential visual fields.

GPA Alerts

  • No progression detected

  • Possible progression

    • 3 or more test points show statistically significant deterioration on 2 consecutive follow-up tests

  • Likely progression

    • 3 or more test points show statistically significant deterioration on at least 3 consecutive follow-up tests

Visual Field Indices and Trend Analysis

  • Visual Field Index (VFI): a trend-based global index that summarizes remaining visual field function.

    • Range: 1% to 100% with 100% representing a perfect age-adjusted visual field.

    • Central VF points are weighted more heavily in calculating the percentage of visual field loss.

    • VFI is derived from an aggregate percentage of visual function, using pattern or total deviations depending on depth of loss.

    • minimum of five examinations over 3 years are needed to calculate VFI

  • VFI interpretation nuances:

    • Higher weight on central field points

    • VFI plotted against age to assess clinical significance of progression rate

    • VFI progression can be accompanied by a regression line and a 3–5 year projection in GPA trend analyses

Minimum Examinations and Age-plots

  • Minimum of five examinations required over 3 years for reliable trend-based evaluation.

  • All VFI values from the examinations are plotted as a function of patient’s age to aid interpretation of the rate and clinical significance of progression.

Rate of Progression and Trend Plots

  • GPA trend analysis provides a global rate of change for the patient’s visual function, represented by the VFI trend and the overall MD/PSD trajectory.

  • Example rate values from the GPA visuals:

    • Example rate: −3.0±0.9%/year (95% confidence)-3.0 \pm 0.9\%/\text{year} \ (95\%\text{ confidence})

    • Slope significance criterion: P < 0.1\% for slope significance

  • The rate of progression is illustrated with a regression line on the VFI plot and a 3–5 year projection of VFI if the current trend continues.

Visual Field Interpretation Workflow

  • Confirm patient and examination parameters (DOB, refractive correction, test pattern).

  • Assess whether the VF plot can be trusted:

    • Review reliability indices, test artefacts, and determine if the test should be repeated.

  • Scan across all sections of the printout:

    • Threshold values, Total Deviation, Pattern Deviation, MD, PSD, VFI, GPA,Cluster Analysis.

  • Describe the VF defect:

    • Depth (Shallow-Deep), Pattern (Diffuse-Localised), Location.

  • Integrate findings into a clinical interpretation considering trend data and GPA classifications.