Clinical Effective Dynamic Range and the Measurement Floor of SITA-Faster Visual Field Tests

Area of Science:

• Ophthalmology
• Visual Psychophysics
• Medical Technology

Background:

• Visual field testing is crucial for diagnosing and monitoring glaucoma and other optic nerve disorders.
• Swedish Interactive Thresholding Algorithm (SITA)-Faster is a common automated perimetry test.
• Understanding the effective dynamic range and reliability of SITA-Faster is essential for accurate clinical interpretation.

Purpose of the Study:

• To determine the effective dynamic range of SITA-Faster perimetry.
• To evaluate the impact of test reliability on SITA-Faster outcomes.
• To define the measurement floor and number of clinical steps for SITA-Faster.

Main Methods:

• Analysis of 9,672 test-retest pairs from 1,468 eyes using SITA-Faster 24-2 visual field tests.
• Utilized three methods (Loess functions, Bland-Altman analysis, Gaussian smoothing with linear regression) to assess outcome measures.
• Examined data from the total cohort, a subgroup with false positive rate ≤15%, and a subgroup with false positive rate of 0%.

Main Results:

• Method 1 identified four clinical steps with a measurement floor of 20-21 dB.
• Methods 2 and 3 indicated a measurement floor between 18-21 dB, with Method 3 revealing additional steps.
• A false positive rate of 0% generally resulted in a lower measurement floor and more breakpoints compared to higher tolerances.

Conclusions:

• SITA-Faster, with a false positive rate ≤15%, demonstrates 4-5 meaningful clinical steps and a measurement floor of 18-21 dB.
• This floor is slightly higher than SITA-Standard, potentially due to SITA-Faster's higher sensitivity and variability.
• For sensitivities below 18-21 dB, alternative perimetric strategies like 10-2 testing or Goldmann size V stimulus are recommended.