Simfield: A Computer Simulated Visual Field Test to Screen for Glaucoma

Abstract

Objective: To evaluate the efficacy of a computer simulated visual field test (Simfield) as a screening tool for glaucoma. Design/Participants/Methods: 36 glaucoma or glaucoma suspect patients (53 eyes) from one ophthalmology clinic between October 2013 and May 2014 used the Simfield program within six months of a reliable performance on a 24-2 SITA standard Humphrey Visual Field Analyzer Exam. The exam measured threshold values at the same 54 points as the 24-2 SITA standard software as well as false positives, false negatives, and fixation losses. Two glaucoma specialists and one general ophthalmologist analyzed the Simfield results in masked fashion and determined whether there was evidence of a glaucomatous defect in any of the 4 quadrants of each field. These results were compared to the corresponding HFA tests to determine sensitivity and specificity. Results: The sensitivity of Simfield ranged from 51-76% and the specificity was 67-88%. In a sub analysis that eliminated mild defects, defined as defects in a field with mean deviation < 7.0, sensitivity improved to 75-91% and specificity was 69-91%. The average false positive rate was 5.2%, the average false negative rate was 3.7%, and the average fixation loss rate was 27.7%. Conclusions: Simfield is an effective test for identifying moderate to severe glaucomatous visual field loss and can be accessed from any home computer. While the cost to detect glaucoma in one patient using current screening methods is estimated at $1000, Simfield can be used for free anywhere that a computer is available.