Page 80 - JSOM Summer 2018

capabilities in reading: The person with worse contrast sen- yellow. The eye is most sensitive to green light and least sensi-
sitivity will have a more difficult time reading and seeing fine tive to red light. The combination of these sensitivities could
2
details. Contrast sensitivity is impaired in many diseases and be why test results under green/red light are similarly to those
4
ophthalmic circumstances, including myopia, glare, dry eyes, performed under white light.

and as an adverse effect of some prescription drugs, as well
as other conditions. During PR testing, performance using Future studies will define the influence of hue selection on
5–8
monochromatic lights and combination blue/red was poor successful completion of simulated Tactical Combat Casualty
compared with performance under illumination with white, Care procedures. Our study group will also seek to quantify
red/green, and red/green/yellow polychromatic lights. The su- threshold values of both hue and intensity/brightness that pre-
periority of the red/green and red/green/yellow combinations dict Operator and casualty loss of concealment under field
in near contrast portends an increased ability of SOFMED conditions. We are also exploring combinations of hue and
providers to differentiate tissues by visual inspection (e.g., brightness to maximize preservation of dark adaptation for
blood versus lymph) using these lights in place of monochro- field and aviation applications.
matic lights. Future studies could explore lighting’s effect on
contrast sensitivity for distance vision instead of near vision, Acknowledgments
as our study has done. We thank First Light-USA for providing us with the Toma-
hawk lights necessary for this study and Rocky Vista Univer-
Visual acuity is defined as the ability to resolve fine detail in a sity Military Medicine Track for its support throughout this
pattern. Reducing the size of a pattern until the smallest pat- project.
9
tern is recognized tests visual acuity. Visual acuity is the most
common test for assessing one’s ability to see, and it is easily Funding
performed. Visual acuity has been studied under suboptimal This work was supported by Rocky Vista University Military
lighting conditions, such as while using night vision goggles. Medicine Track.
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During our visual acuity testing, all monochromatic and poly-
chromatic lights preserved visual acuity with the exception of Disclosures
individual blue light. This was unexpected, because blue light The authors have indicated they have no financial relation-
has become commonplace as a tactical light and even preferred ships relevant to this article to disclose.
by most SOFMED personnel. All lights except blue, therefore,
1
were equally efficacious in our study in preserving one of the Author Contributions
most basic tenants of vision: visual acuity. JPVB, JW, and JM formed the medical student team that de-
signed the experiment, collected data, and wrote manuscript
PiP testing is a way to screen for color vision deficits but is drafts. AL, RWE, and CC formed the faculty team that ap-
not specific for certain types of color blindness. In contrast, proved the experiment design, analyzed data, and edited and
10
the FD15 test is not only sensitive for detecting color deficits approved manuscript drafts. All authors approved the final
but also is specific to various types. In our study, results of version of this draft.
10
FD15 testing were best with white light. We hypothesized that
green/red, or at least green/red/yellow, would perform well in References
these tests because they contain both long and medium wave- 1. Calvano CJ, Enzenauer RW, Eisnor DL, et al. Tactical lighting in
lengths of light in the visual spectrum. However, the absence special operations medicine: survey of current preferences. J Spec
of short wavelength (i.e., blue) light makes color discrimina- Oper Med. 2013;13(4):15–21.
tion difficult. Green/red and green/red/yellow light’s strong 2. Pedler M, Ruiz F, Lamari M, et al. Red-green versus blue tactical
light: a direct objective comparison. J Spec Oper Med. 2016;16
performance in PiP testing may due to the fact that the plates (4):54–58.
have many green and red hues that are easily brought out by 3. Pelli D, Bex P. Measuring contrast sensitivity. Vision Res. 2013;
the green, red, and yellow in the lights. Regardless, this can be 90:10–14.
seen as an attribute for these lights in SOFMED applications, 4. Brown B. Reading performance in low vision patients: relation
because being able to identify red blood is important in these to contrast and contrast sensitivity. Am J Optom Physiol Opt.
operations, which often involve traumatic and bloody events. 1981;58(3):218–226.
5. Collins J, Carney L. Visual performance in high myopia. Curr Eye
Res. 1990;9(3):217–223.
Limitations 6. Abrahamson M, Sjostrand J. Impairment of contrast sensitivity
This study was limited by the number of participants. The re- function as a measure of disability glare. Invest Ophthalmol Vis
sults would be more reliable if we had more participants. Also, Sci. 1986;27:1131–1136.
this study did not take into account the effect of corrective 7. Rolando M, Lester M, Macri A, et al. Low spatial-contrast sensi-
contact lenses or glasses on the results. tivity in dry eyes. Cornea. 1998;17(4):376–379.
8. Li J, Tripathi R, Tripathi B. Drug-induced ocular disorders. Drug
Saf. 2008;31(2):127–141.
Conclusion 9. Neitz M, Green DG, Neitz J. Visual acuity, color vision, and ad-
aptation. In: Albert DM, Miller JW, Azar DT, Blodi BA, eds. Al-
This study aimed to test which hue of light preserved visual bert & Jakobiec’s Principles and Practice of Ophthalmology. 3rd
acuity, contrast sensitivity, and color vision when compared ed. Amsterdam, The Netherlands; Elsevier; 2008:chap 123.
with a white-light standard in a low-light setting. These as- 10. DeVilbiss C, Antonio J, Fiedler G. Night vision goggle (NVG)
pects of vision are preserved to a greater degree, as we pre- visual acuity under ideal conditions with various adjustment pro-
cedures. Aviat Space Environ Med. 1994;65(8):705–709.
dicted, by green/red combination lights, including green/red/

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