Methods for visual field testing

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

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 Spearmann 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.

Bowl / Tangent screen trigonometric relations

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

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

Kinetic vs. Static methods:
In general, kinetic methods are used in manual perimetry and static methods are used in automated visual field testing. However, kinetic perimetry can make use of static methods, and kinetic perimetry can be performed by some automated perimeters.

Errors in Visual Field Testing
Errors common to all methods:

Informed and accurate interpretation of visual fields depends on careful consideration of all the information in the visual field printout. No portion should be attended to the exclusion of others. Determining whether a patient’s visual field has improved,  deteriorated, or remained stable over time remains the greatest challenge in visual field interpretation and a fundamental consideration in the management of glaucoma. Several clinical trials have found that distinguishing true glaucomatous change from random variability requires multiple confirming visual fields. This was shown by the Ocular Hypertension Treatment Study (OHTS), where 88% of initial glaucomatous visual field deficits were not validated on a repeat visual field examination. Because sequences of any two visual fields within the same patient can indicate worsening, recovery, or stability, long-term trends are best appreciated by examining the patient’s full chronological set of visual fields, rather than simply comparing the two most recent fields to each other.

Other errors common to kinetic perimetry:

Other errors common to automated :

 Other errors common to the tangent screen:

Other errors common to Goldmann perimetry: