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Justin Hellman, Marie E Perrone, Diego Altamirano, Lili Farrokh-Siar, Anupama Anchala, Susan Ksiazek; Simfield: A computer simulated visual field test to screen for glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5622.
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To evaluate the efficacy of a computer simulated visual field test (Simfield) as a screening tool for glaucoma.
19 glaucoma or glaucoma suspect patients (29 eyes) from one ophthalmology clinic used the Simfield program within six months of a reliable performance on a 24-2 SITA standard Humphrey Visual Field Analyzer (HFA) Exam. Reliability was defined as having the two most recent HFA exams with absolute value of the difference in mean deviation ≤ 1 and fixation losses, false positives, and false negatives all < 20%. Patients with corrected vision worse than 20/100 were excluded. Each patient was placed 30 cm from the 19 inch screen with a patch on one eye and the blind spot was identified. The exam then measured threshold values at the same 54 points as the 24-2 SITA standard software used by the HFA as well as false positives, false negatives, and fixation losses. One glaucoma specialist and one general ophthalmologist blindly analyzed the Simfield results 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. A defect on a HFA test was defined as a pattern typical of glaucoma in a field with five or more points of p <5% with a cluster of three or more abnormal points of p <5%, or two or more points of p <1%.
The sensitivity of Simfield ranged from 53-66% and the specificity was 83-88%. In a subanalysis that eliminated mild defects, defined as defects in a field with mean deviation < 7.0, sensitivity improved to 80-84% and specificity was 83-91%. The average false positive rate was 4.1%, the average false negative rate was 5.5%, and the average fixation loss rate was 35.8%.
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. Future efforts will aim to improve fixation loss and the ability to detect mild glaucomatous defects more effectively.
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