DOD-Funded Researcher Studies the Impact of Primary Blast Injuries on the Eye

Featured speaker T. Vicky Nguyen, Ph.D. (Johns Hopkins University)

On March 19, AEVR’s Decade of Vision 2010-2020 Initiative hosted a Congressional briefing entitled Computational Model of the Eye for Primary Blast Injury featuring T. Vicky Nguyen, Ph.D. from the Department of Mechanical Engineering at Johns Hopkins University. Dr. Nguyen’s research is funded by the Peer Reviewed Vision Trauma Research Program (VTRP) within the Department of Defense (DOD) and addresses several DOD-identified vision research gap-the immediate impact of blast injuries on ocular structures; the potential long-term impact on visual processing, such as visual dysfunction associated with Traumatic Brain Injury (TBI); and the need for better protective gear.

Dr. Nguyen was introduced by joint DOD/Department of Veterans Affairs (VA) Vision Center of Excellence (VCE) Director Colonel Donald Gagliano, M.D., who explained that deployment-related military eye trauma is very different from the trauma associated with falls, vehicle accidents, and blunt force trauma. He noted that, to adequately protect the eye in combat situations, the source of the trauma must be understood, which is the focus of Dr. Nguyen’s work.

Dr. Nguyen explained that, unlike past conflicts where ocular injuries resulted from exploding munitions, more than 70 percent of blast injuries in the conflicts in Iraq and Afghanistan have resulted from Improvised Explosive Devices (IEDs). Blasts are characterized as primary (shock wave), secondary (propelled fragments that cause corneal laceration, eye globe penetration and perforation), tertiary (blunt force trauma that causes closed globe injuries such as retinal detachment and optic nerve damage and orbital fractures), and quaternary (burns, toxins, radiological and biological contamination). Although most of these result in ocular damage that is immediately recognized, the distortion of ocular structures can result in the long-term development of optical dysfunction that may not be diagnosed until many years later.

Dr. Nguyen has developed an experimentally validated computational model of the human eye globe to investigate injury mechanisms of the primary blast wave. This includes determining the stresses and deformations of the eye-wall (the cornea, the lens at the front of the eye, and sclera) and internal ocular structures (such as the retina, the light-sensitive back of the eye, and the optic nerve), as well as investigating the interaction of orbital structures with the blast wave and the potential mitigating impact of standard eye armor.

In the computational model, blasts are directed head-on and from various angles sideways and upwards at a rigid face with all anatomical features, which can be varied to reflect gender or ethnicity. When blasts are directed head-on, the eye is a “hot spot” in that the brow and nose act as a deflector to move pressure onto the eye. The pressure is also asymmetric, focusing off-center toward the nose, raising the possibility of damage to the ocular muscles and even bone. Sideway blasts ranging in angles from 40 to 80 degrees result in similar injuries, while blasts directed upwards from the ground are less severe due to the protective nature of the chin and nose.

When the model is revised to reflect eye armor, the head-on blast initially focuses on the eye, then funnels around the armor toward the temple, not the nasal region. There is still a pressure increase on the eye, although less than without armor. This can occur especially when the armor is not properly fitted, enabling a gap at the bottom for “underwash” to affect the eye. “Although eye armor provides some degree of protection from the blast wave, it is not as effective as we think it is,” said Dr. Nguyen.

She stressed that, although the computational model provides an efficient tool to investigate stresses and deformations cause by blasts, it must be complemented by actual physical experimentation into the material properties of tissue, translating the deformation and pressures to injury risk, and validating the deformation and pressures. In that regard, she uses a shock tube inflation test in which shock waves are directed at bovine eyes, and the resulting measurements are translated into the computational model for validation.

She concluded by stating that, “This basic research will lead to improved armor design to protect today’s warfighter from the debilitating effects of IED-related ocular blast trauma.”

Dr. Nguyen was one of twelve domestic and international researchers who received a total of $11 million in funding from the DOD’s Vision Trauma Research Program (VTRP) in its Fiscal Year (FY) 2009/2010 cycle, which is managed by the Telemedicine and Advanced Technology Research Center (TATRC). In the FY2011/2012 funding cycle, TATRC awarded $14 million in grants to 21 researchers. H.R. 933, the bill to finalize FY2013 appropriations, funds the VTRP at $10 million, which nets to $9.2 million after the sequester’s eight percent cut.

Dr. Nguyen also recently was awarded a National Science Foundation CAREER Award, for her work on the growth of collagenous tissues.

NAEVR Executive Director James Jorkasky began the session by citing NAEVR’s 2012 study that military eye injury and blindness has cost the United States $25.1 billion in the 2000-2010 timeframe	Colonel Donald Gagliano, M.D., Director of the Joint DOD/VA Vision Center of Excellence, provided a welcome and explained how Dr. Nguyen’s work is addressing several DOD-identified vision research gaps
Left to right: Rebecca Hyder (American Academy of Ophthalmology) and Mary Lawrence, M.D., M.P.H, who serves as the Deputy Director of the VCE	Left to right: Felix Barker, O.D., the VCE’s Associate Director of Research, with Tom Zampieri, Ph.D. (Blinded Veterans Association)