Detecting Glaucomatous Visual Field Change: A Comparison of the New Field Damage Likelihood Score (FDLS) with Existing Field Staging Systems

Abstract

Abstract: : Purpose: Currently accepted visual field staging systems use relatively few stages and may not be sensitive to measure glaucomatous change. Systems with many stages may be clinically difficult to use. The Field Damage Likelihood Score (FDLS), a new scale for visual field interpretation is designed to balance ease of use with sufficient discrimination to detect visual field change. We compared the FDLS visual field system and several other staging systems to detect glaucomatous field change. Methods: Baseline fields from Wills Eye Hospital patients enrolled in the CIGTS trial were examined. Fields were evaluated in alphabetical order and classified according to clinical impression by a glaucoma specialist as "no damage," "mild," "moderate," and "severe" glaucoma until 10 examples of each level of damage were identified for inclusion in the study. The most recent study field from each selected eye was obtained and designated as follow-up field for comparison. The specialist was masked to field chronology and simultaneously evaluated the two fields for each patient to determine if the field was stable, showed glaucomatous worsening, or improvement. This evaluation was considered the standard for comparison. Four different masked observers were asked to stage each field according to the FDLS, the Hodapp-Parrish-Anderson (HPA) stage and the Glaucoma Staging System (GSS). Each field pair was described as "worse", "stable" or "better" according to direction and amount of movement in each staging system. Levels of agreement between reference standard and observers within various systems were tabulated. Results: Table 1 shows the overall levels of exact agreement for three field staging scales regardless of direction and amount of change. Regardless of the amount of change, the FDLS performed better across all four observers. Table 1: Overall level of exact agreement with expert opinion for 3 field staging scales by four observers Conclusion: The FDLS scale for interpretation of visual fields shows greater agreement with expert evaluation regardless of degree of change.  

Keywords: visual fields • perimetry • clinical research methodology