Research article

Development and validation of a computerized expert system for evaluation of automated visual fields from the Ischemic Optic Neuropathy Decompression Trial

Steven E Feldon¹ , Lori Levin² , Roberta W Scherer³ , Anthony Arnold⁴ , Sophia M Chung⁵ , Lenworth N Johnson⁶ , Gregory Kosmorsky⁷ , Steven A Newman⁸ , Joanne Katz³ , Patricia Langenberg⁹ , P David Wilson⁹ , Shalom E Kelman⁹ , Kay Dickersin³ and members of the Ischemic Optic Neuropathy Decompression Trial Research Group

¹  Department of Ophthalmology, University of Rochester School of Medicine, Rochester, NY, USA

²  Office of the Provost, University of Southern California School of Medicine, Los Angeles, Ca, USA

³  Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Md, USA

⁴  Department of Ophthalmology, Jules Stein Eye Institute, Los Angeles, Ca, USA

⁵  Department of Ophthalmology, Saint Louis University Eye Institute, St. Louis, Mo, USA

⁶  Department of Ophthalmology, University of Missouri's Mason Eye Institute, Columbia, Mo, USA

⁷  Department of Neurophthalmology, Division of Ophthalmology, Cole Eye Institute, The Cleveland Clinic Foundation, Cleveland, Oh, USA

⁸  Department of Ophthalmology, University of Virginia, Charlottesville, Va, USA

⁹  Department of Ophthalmology, University of Maryland School of Medicine, Baltimore, Md, USA

author email corresponding author email

BMC Ophthalmology 2006, 6:34doi:10.1186/1471-2415-6-34

Published:	20 November 2006

Abstract

Background

The objective of this report is to describe the methods used to develop and validate a computerized system to analyze Humphrey visual fields obtained from patients with non-arteritic anterior ischemic optic neuropathy (NAION) and enrolled in the Ischemic Optic Neuropathy Decompression Trial (IONDT). The IONDT was a multicenter study that included randomized and non-randomized patients with newly diagnosed NAION in the study eye. At baseline, randomized eyes had visual acuity of 20/64 or worse and non-randomized eyes had visual acuity of better than 20/64 or were associated with patients refusing randomization. Visual fields were measured before treatment using the Humphrey Field Analyzer with the 24-2 program, foveal threshold, and size III stimulus.

Methods

We used visual fields from 189 non-IONDT eyes with NAION to develop the computerized classification system. Six neuro-ophthalmologists ("expert panel") described definitions for visual field patterns defects using 19 visual fields representing a range of pattern defect types. The expert panel then used 120 visual fields, classified using these definitions, to refine the rules, generating revised definitions for 13 visual field pattern defects and 3 levels of severity. These definitions were incorporated into a rule-based computerized classification system run on Excel^® software. The computerized classification system was used to categorize visual field defects for an additional 95 NAION visual fields, and the expert panel was asked to independently classify the new fields and subsequently whether they agreed with the computer classification. To account for test variability over time, we derived an adjustment factor from the pooled short term fluctuation. We examined change in defects with and without adjustment in visual fields of study participants who demonstrated a visual acuity decrease within 30 days of NAION onset (progressive NAION).

Results

Despite an agreed upon set of rules, there was not good agreement among the expert panel when their independent visual classifications were compared. A majority did concur with the computer classification for 91 of 95 visual fields. Remaining classification discrepancies could not be resolved without modifying existing definitions.

Without using the adjustment factor, visual fields of 63.6% (14/22) patients with progressive NAION and no central defect, and all (7/7) patients with a paracentral defect, worsened within 30 days of NAION onset. After applying the adjustment factor, the visual fields of the same patients with no initial central defect and 5/7 of the patients with a paracentral defect were seen to worsen.

Conclusion

The IONDT developed a rule-based computerized system that consistently defines pattern and severity of visual fields of NAION patients for use in a research setting.