Visual Field Testing 24º central degrees (fast threshold 3 db steps) using virtual reality glasses

Virtual Reality Glasses

A Portable Low-cost Visual Field Test. A technology that is more than 10 times cheaper than the common visual field tests in use.

The device utilizes off-the-shelf virtual reality glasses and a smartphone, to provide a visual field test / virtual perimeter that it is lightweight, portable, accurate and economical.

Bibliography

Visual field examination method using virtual reality glasses compared with the Humphrey perimeter. Tsapakis S, Papaconstantinou D, Diagourtas A, Droutsas K, Andreanos K, Moschos MM, Brouzas D. Clin. Opht. 2017:11;1431-43

 (The software is free for non profit use)

 

Visual field test results using virtual reality glasses compared to Humphrey Perimeter

20 eyes of 10 patients consecutively presented at visual fields lab were tested successively using Humphrey perimeter (30-2, 76 points) and virtual reality glasses method (fast threshold 3db steps algorithm at central 24º, 52 points of visual field). The results were statistically analyzed and compared.

Trust EXOS 3D virtual reality glasses and Alcatel One Touch Pixi 4 (6) 8050D smartphone with 6" display were used for the tests. Smartphone brightness was set at a point that makes all 25 distinct shades of gray clearly visible. This is about 50% of maximum available brightness.

The patients tolerated the virtual reality visual field test very well. All the patients reported that it was much more comfortable compared to the standard perimeter (bowl) test. 

Point to point correlation coefficient (r) between the virtual reality glasses method and the Humphrey perimeter was computed for each eye and for all eyes together using the Instat version 3.05 of GraphPad Software, Inc. When values distribution was not normal the nonparametric Spearman correlation coefficient (r) was used.

Virtual Reality Glasses tests were 24 º (52 points) while Humphrey tests were 30 º (76 points). Only the corresponding (common 52 points) between these were taken into consideration. 

Results

EYE

SPEARMAN (r)

SD

P (one-tailed)

1

0.736955

6.594795

P<0.0001

2

0.765154

4.90298

P<0.0001

3

0.875855

5.1637

P<0.0001

4

0.792082

2.449182

P<0.0001

5

0.773847

3.754133

P<0.0001

6

0.75502

5.163674

P<0.0001

7

0.865649

2.717742

P<0.0001

8

0.833976

6.698726

P<0.0001

9

0.838132

2.870508

P<0.0001

10

0.766863

5.146533

P<0.0001

11

0.870688

2.422245

P<0.0001

12

0.848471

2.828427

P<0.0001

13

0.850762

2.313561

P<0.0001

14

0.889794

2.154654

P<0.0001

15

0.745111

9.614359

P<0.0001

16

0.829142

3.223862

P<0.0001

17

0.725046

5.796804

P<0.0001

18

0.806027

3.376511

P<0.0001

19

0.879466

3.225733

P<0.0001

20

0.722703

4.385763

P<0.0001

  Total  Results

SPEARMAN (r)

MEAN SD

P(one-tailed)

0.808537

4.19494

P<0.0001

In each eye and in all eyes together the mean difference value between the two methods was statistically significant at P < 0.0001.

The correlation coefficient (r) in all tests between the two methods was statistically extremely significant at P < 0.0001.

  • Alternative method - Automated tangent screen visual field test - PC automated (tangent screen) visual field: the patient sits comfortably in front of a monitor/projector screen and asked to stare/focus on the target at the center of the screen. The software flashes small lights at different locations within the screen's surface. The lights are bright or dim at different stages of the test. Some of the flashes are purely to check the patient is concentrating. The eye that is not being tested is covered. Each eye is tested separately. Both eyes are refracted to the best corrected vision. Pupils are not usually dilated. A mouse is given to the patient to be used during the test. The patient clicks the left mouse button whenever a light is seen and the right mouse button to pause the test. The software records the spot of each flash and if the patient pressed the button when the light flashed in that spot. The responses are used to determine the presence of defects within the visual field.  The patient should allow 10-20 minutes to have the whole test. The software then automatically maps and calculates the patient's visual field. Patients changing from one visual field test program to another should establish a new baseline.

    To check false-positive responses, the program includes stimulus intervals without presenting a target and records the number of times that the patient responds during these intervals. This helps identify the “trigger happy” patient.

    Fixation losses are monitored by intermittently projecting a stimulus in the location of the blind spot and determining whether or not the patient responds. A patient who sees the blind spot stimulus may be making eye movements and not maintaining fixation. If excessive fixation losses still occur, the examiner should observe the eye directly to determine whether the patient is fixating steadily or looking around. Several multi center clinical trials and research investigations have shown that most patients can perform reliable visual fields tests when carefully tested and appropriately monitored.

    Short-term fluctuation (SF) indicates the amount of variability exhibited by the patient during the test procedure. It is determined by performing a second threshold determination at 8 pre-selected visual field locations and  calculating the average variation of the repeated measures for these points.

    May be the procedure of choice for certain conditions / patients who cannot maintain fixation in a bowl perimeter, patients with severe arthritis or handicap or patients who cannot place chin in chin-rest of bowl perimeters. Automated tangent screen visual field testing is much like automated bowl visual field test except that a tangent screen is used instead of a bowl. Cost effective method.

Bibliography

    1. Visual field examination using a video projector: comparison with Humphrey perimeter. Brouzas D, Tsapakis S, Nitoda E, Moschos M. Clin. Opht. 2014:8;523-8

Bowl / Tangent screen trigonometric relations

(Video projectors, CRTs and plasma screens give better results than LCDs because they produce deeper black then LCDs)
 

Alternative method: Computer monitor (tangent screen visual field test)
(22"-26" computer monitor. monitor arm,  head/chin rest, netbook, motorized instrument table, software)


DM7220S-BT Econoview Double Arm


LCD and Heavy Duty Chin Rest

Video projector (short throw) tangent screen visual field test


Small Size Projection Screen 120 cm


Small Size Projection Screen 120 cm


 

Comparison : Automated tangent screen visual field test vs. Bowl visual field test