The influence of sampling errors on test-retest variability in perimetry.

Area of Science:

• Ophthalmology
• Visual Science

Background:

• Standard automated perimetry (SAP) is a key tool for assessing visual fields.
• Understanding factors influencing SAP test-retest variability is crucial for accurate diagnosis and monitoring of visual field defects.

Purpose of the Study:

• To investigate if higher spatial frequencies distort visual fields measured by SAP.
• To determine if fixational drift, stimulus size, and sampling density explain SAP test-retest variability.

Main Methods:

• Analyzed amplitude spectra of Humphrey Field Analyser (HFA) 10-2 fields for spatial frequencies.
• Constructed model visual fields with similar spectra to 10-2 fields.
• Examined test-retest variability using various Goldmann stimulus sizes and simulated fixation drifts.

Main Results:

• HFA 10-2 fields contained spatial frequencies up to 0.25 cyc/deg, exceeding SAP grid resolution.
• Test-retest variability increased with scotoma depth.
• Larger stimuli (Goldmann III-VI) and reduced fixation jitter decreased test-retest variability.

Conclusions:

• Simulated fixation drift, smaller than typical, reproduced key SAP test-retest variability features.
• Employing larger, slightly blurred stimuli with potential overlap may reduce test-retest variability in SAP.
• Avoiding meridian overlap in stimulus placement might be beneficial for perimetric testing.