Page 79 - JSOM Summer 2018

TABLE 1 Statistical Comparison of Light Hues to a White Light Standard
Color of Light
Green/Red/
Test White Green Red Green/Red Yellow Blue Blue/Red
PR contrast μ = 1.92 μ = 1.80 μ = 1.69 μ = 1.89 μ = 1.92 μ = 1.74 μ = 1.835
sensitivity a SD = 0.144 SD = 0.160 SD = 0.157 SD = 0.151 SD = 0.114 SD = 0.179 SD = 0.156
SEM = 0.0263 SEM = 0.0292 SEM = 0.0287 SEM = 0.0276 SEM = 0.0208 SEM = 0.326 SEM = 0.0284
t = 5.77 t = 8.33 t = 1.42 t = 0.00 t = 6.38 t = 2.96
p < .001 p < .001 p > .16 p > .99 p > .99 p < .007
Tumbling E μ = 0.5 μ = 0.5 μ = 0.5 μ = 0.5 μ = 0.5 μ = 0.385 μ = 0.5
visual acuity b SD = 0 SD = 0 SD = 0 SD = 0 SD = 0 SD = 0.111 SD = 0
SEM = 0 SEM = 0 SEM = 0 SEM = 0 SEM = 0 SEM = 0.0203 SEM = 0
t = 0.00 t = 0.00 t = 0.00 t = 0.00 t = 5.68 t = 0.00
p > .99 p > .99 p > .99 p > .99 p < .001 p > .99
FD15 color μ = 3.7 μ = 88.3 μ = 34.8 μ = 27.1 μ = 26.9
vision c SD = 7.42 SD = 28.2 SD = 17.6 SD = 5.97 SD = 6.03
SEM = 1.35 SEM = 5.14 SEM = 3.22 SEM = 1.09 SEM = 1.10 Not Not
t = –16.8 t = –8.77 t = –15.0 t = 14.9 performed performed
p < .001 p > .001 p > .001 p ≤ .001
PiP color μ = 0.533 μ = 7.07 μ = 3.5 μ = 0.267 μ = 0.267
vision d SD = 0.681 SD = 1.98 SD = 1.04 SD = 0.520 SD = 0.520
SEM = 0.124 SEM = 0.361 SEM = 0.190 SEM = 0.0951 SEM = 0.0951 Not Not
t = 16.2 t = 13.7 t = 1.86 t = 1.77 performed performed
p < .001 p < .001 p < .074 p < .09
All reported t values have 29 degrees of freedom. FD15, Farnsworth D-15 color-vision test; PiP, pseudoisochromatic plate; PR, Pelli-Robson
Near Contrast Sensitivity test.
a Means are given as log contrast sensitivity scores.
b Means of visual acuities.
c Means of error scores.
d Means of the number incorrect.

P ≥ .05 indicated no statistically significant difference between red lights as compared with white light (p < .001). Perfor-
performance with white light and the tested light hue (i.e., the mance when polychromatic green/red and green/red/yellow
tested light hue was just as effective as white when the partici- lights were used was just as effective as white in PiP color-
pant performed that particular test). vision testing (p = .073 and .088, respectively).

Results Discussion
The 30 participants performed the multiple tests of visual SOFMED has a need for improved tactical lighting. This need
function. The results under different light conditions were was made clear in a study by Calvano et al. Their prelimi-
1
compared with a white-light standard and are listed in Table 1. nary study showed that no ideal hue had been identified for
SOFMED Operators’ work, that SOF Operators carried more
PR Contrast Sensitivity than one light for their purposes, and that the lights are not
Results of contrast sensitivity testing using monochromatic night-vision capable. Most importantly, their study showed
1
blue, green, and red light, along with polychromatic blue/red that 25% of the current light being used led to poor casualty
light were worse when compared with testing using white light outcomes. 1
(p < .006). Results of contrast sensitivity testing using multihue
combination green/red (p > .99) and green/red/yellow (p > .16) There are three aspects that need to be considered when
light were comparable with those when white light was used. choosing a tactical light for SOFMED. A tactical light must
(1) provide enough luminance to accomplish the task, (2) not
Tumbling E Visual Acuity be too bright so as to compromise stealth in the field, and (3)
Monochromatic blue light (p < .001) was the only light hue when the light is turned off, the light must allow for quick ad-
for which participants’ results on visual acuity testing were aptation back to dark conditions, because vision must recover
worse than when testing was performed using white light. Par- quickly to see as much as possible in the dark. 2
ticipants’ test results when polychromatic blue/red, green/red,
and green/red/yellow, as well as monochromatic green and red The current study focused on the first aspect of tactical light-
light were used were similar to those recorded when tested ing, that is, which tactical light preserves the basic aspects of
using white light (p > .99 for all). vision, thereby providing enough luminance to accomplish
tasks in the field? We found no other published research that
FD15 Color Vision used different light wavelengths to assess contrast sensitivity,
Participants’ color perception, as measured with the FD15 test, visual acuity, or color vision.
was significantly worse than with white light (p < .001 for all).
Contrast sensitivity defines the threshold between the invisi-
3
PiP Color Vision ble and visible world. It is the eye’s ability to discern slight
Participants’ color perception using PiP plates was signifi- differences between objects. Two people with the same visual
cantly worse with monochromatic green and monochromatic acuity and different contrast sensitivities will have different

The Effect of Light Hue on Vision Testing | 77