Accuracy and Feasibility of an Android-Based Digital Assessment Tool for Post Stroke Visual Disorders-The StrokeVision App

Abstract

Background: Visual impairment affects up to 70% of stroke survivors. We designed an app (StrokeVision) to facilitate screening for common post stroke visual issues (acuity, visual fields, and visual inattention). We sought to describe the test time, feasibility, acceptability, and accuracy of our app-based digital visual assessments against (a) current methods used for bedside screening and (b) gold standard measures.

Methods: Patients were prospectively recruited from acute stroke settings. Index tests were app-based assessments of fields and inattention performed by a trained researcher. We compared against usual clinical screening practice of visual fields to confrontation, including inattention assessment (simultaneous stimuli). We also compared app to gold standard assessments of formal kinetic perimetry (Goldman or Octopus Visual Field Assessment); and pencil and paper-based tests of inattention (Albert's, Star Cancelation, and Line Bisection). Results of inattention and field tests were adjudicated by a specialist Neuro-ophthalmologist. All assessors were masked to each other's results. Participants and assessors graded acceptability using a bespoke scale that ranged from 0 (completely unacceptable) to 10 (perfect acceptability).

Results: Of 48 stroke survivors recruited, the complete battery of index and reference tests for fields was successfully completed in 45. Similar acceptability scores were observed for app-based [assessor median score 10 (IQR: 9-10); patient 9 (IQR: 8-10)] and traditional bedside testing [assessor 10 (IQR: 9-10); patient 10 (IQR: 9-10)]. Median test time was longer for app-based testing [combined time to completion of all digital tests 420 s (IQR: 390-588)] when compared with conventional bedside testing [70 s, (IQR: 40-70)], but shorter than gold standard testing [1,260 s, (IQR: 1005-1,620)]. Compared with gold standard assessments, usual screening practice demonstrated 79% sensitivity and 82% specificity for detection of a stroke-related field defect. This compares with 79% sensitivity and 88% specificity for StrokeVision digital assessment.

Conclusion: StrokeVision shows promise as a screening tool for visual complications in the acute phase of stroke. The app is at least as good as usual screening and offers other functionality that may make it attractive for use in acute stroke.

Clinical trial registration: https://ClinicalTrials.gov/ct2/show/NCT02539381.

Keywords: apps; assessment; hemianopia; information technology; sensitivity; specificity; stroke; visual neglect.

Figures

Figure 1

Tumbling E Near Acuity Test, adapted from the android-based distance optotype test, “peek acuity lite” (14.5). The patient is asked to swipe in the direction of the limbs of the E and a staircasing algorithm detects the threshold acuity level.

Figure 2

(A) The StrokeApp Visual Field test. The fixation target is the red nose of the smiling face graphic. The fixation target moves to the extreme corners of the device screen and the black circular target emerges from the periphery toward fixation. The peripheral target (black circle) subtends a similar angle to the Goldmann III target setting. The patient is encouraged to tap anywhere on the screen at the moment they detect the emerging peripheral target. The tester observes patient fixation, and if a fixation loss is detected, the screen is swiped to delete the previous input and re-test that point or quadrant. (B) The diagonal hashed lines indicate field defect once reaction time has been accounted for. The red line indicates limit of the visual field before reaction time has been accounted for. (C) StrokeSim. The detected perimetry plot is transposed as a digital filter to the feed from the device back-facing camera. The field within the defect is averaged to a single color.

Figure 3

(A) The Line Crossing test screen. Line thickness is calibrated against the acuity score to allow testing in low-vision patients. The patient is asked to press the perceived center of each line. (B) The Face Cancelation Test. A second test of inattention, whereby the patient is asked to press the small faces. As previous, line thickness is calibrated to acuity score.