“VisualFields Easy”: an iPad Application as a Simple Tool for Detecting Visual Field Defects
Angelane S. Santos, MD, Evelyn S. Morabe, MD
This study aims to determine the reliability of the “VisualFields Easy” application in detecting visual field loss among ophthalmology patients; and to determine the sensitivity, specificity, positive predictive and negative predictive values of this examination using the Humphrey Visual Field Analyzer as the gold standard.
Methods: This is an analytical study that enrolled subjects requiring visual field examination as part of the
comprehensive evaluation of their ophthalmologic condition. Each subject was tested using the standard automated Humphrey Field Analyzer (Carl Zeiss Meditec, Inc., Germany) with the 30-2 Swedish Interactive Thresholding Algorithm (SITA) and the “VisualFields Easy” application (background = 10 cd/m2; size V target; 16-dB stimulus) loaded in an iPad 2 ver. 8.3. The print outs of each test were then interpreted independently by the principal investigator and verified by a glaucoma specialist as positive or negative for visual field defects and computation for sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were done.
Results: The study included 137 eyes of 77 patients, 52 (68%) females and 25 (32%) males, age ranging from 18 to 82 years with a mean (SD) of 58 (+ 14) years. The mean test duration for the standard Humphrey perimetry was 7 minutes 50 seconds (SD + 0.08s), and 3 minutes 21 seconds (SD + 0.01s) for the “VisualFields Easy”. Correlations of False Positives and False Negatives between the 2 tests were p=0.02 and p=0.03 respectively and that there was no statistically significant difference between the reliability parameters of the two tests. There were a total of 74 positives and 63 negatives visual field defects for the Humphrey. These were considered as the True Positive (TP) and True Negative (TN) values. For the “VisualFields Easy”, there were 67 positives and 70 negatives. The results of the “VisualFields Easy” were plotted against the Humphrey perimetry. Sensitivity was computed at 91% and specificity at 100%. Likewise the Positive Predictive Value (PPV) was computed to be 100% and the Negative Predictive Value (NPV) was computed at 90%.
The “VisualFields Easy” application is a quick, easily accessible and fairly reliable way of measuring visual field abnormalities, both for glaucoma and neuro-ophthalmology patients. The application is not intended to replace standard automated perimetry machines, but it may have a role in detecting, documenting and monitoring visual field defects in low resource settings where visual field tests are not available.
Keywords: visual fields, perimetry, visual fields easy, visual field defects, glaucoma