December 2011
Volume 52, Issue 13
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Anatomy and Pathology/Oncology  |   December 2011
Paintball Trauma and Mechanisms of Optic Nerve Injury: Rotational Avulsion and Rebound Evulsion
Author Affiliations & Notes
  • William E. Sponsel
    From the WESMD Professional Association, San Antonio, Texas;
  • Walt Gray
    the Department of Geological Sciences, University of Texas at San Antonio, San Antonio, Texas;
  • Sylvia L. Groth
    the University of Minnesota Medical School, Minneapolis, Minnesota;
  • Amber R. Stern
    the Mechanical Engineering Department, University of Missouri at Kansas City, Kansas City, Missouri; and
  • James D. Walker
    the Engineering Dynamics Department, Mechanical and Materials Engineering Division, Southwest Research Institute, San Antonio, Texas.
  • Corresponding author: William E. Sponsel, 311 Camden Street, Suite 306, San Antonio, TX 78215; sponsel@earthlink.net
Investigative Ophthalmology & Visual Science December 2011, Vol.52, 9624-9628. doi:10.1167/iovs.11-8472
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      William E. Sponsel, Walt Gray, Sylvia L. Groth, Amber R. Stern, James D. Walker; Paintball Trauma and Mechanisms of Optic Nerve Injury: Rotational Avulsion and Rebound Evulsion. Invest. Ophthalmol. Vis. Sci. 2011;52(13):9624-9628. doi: 10.1167/iovs.11-8472.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose.: Ballistic impact studies and supercomputer modeling were performed to elicit the mechanisms of optic nerve rupture that may accompany blunt ocular trauma.

Methods.: Paintball ocular impact responses were studied with abattoir-fresh porcine eyes. Physics-based numerical code CTH was used to produce robust geometric and constitutive models of the eye and orbit, providing a comparative 3-D finite volume model to help determine the mechanisms underlying empirical ballistic observations.

Results.: Among 59 porcine eye specimens submitted to paintball impact in the 1- to 13-J range, 10 (17%) disengaged completely from the orbital mount. In each instance the paintball penetrated the orbit adjacent to the globe, producing rotation and eventual globe repulsion, dramatically evident on high-speed film images. Supercomputer modeling yielded similar globe-expulsive results when orbital constraints were in place, but not when these were removed. In these models, tangential (grazing) impact sheared the nerve flush with the globe via a strain rate effect within 260 μs, with minimal posterior displacement and just 5° of globe rotation. Midperipheral impact produced compressive globe distortion and posterior displacement, followed by rebound and tractional nerve avulsion 10 mm behind the lamina after 700 μs and 20° of globe rotation.

Conclusions.: Constitutive modeling studies suggest at least two trajectory-dependent mechanisms for optic nerve rupture with paintball impact on the eye. Tangential glancing blows produce strain-rate rotational avulsion, abscising the optic nerve with minimal internal globe disruption, whereas off-center direct impact produces slower rotational-rebound evulsion, traumatizing the globe and breaching the nerve posteriorly. The latter mechanism would be expected to arise more commonly and would most likely be clinically masked by accompanying intraocular injury.

The mechanism of traumatic dissociation of the optic nerve from the globe has been a source of clinical intrigue for over a century. In his classic 1909 initial review, 1 Jameson Evans distinguished between slower traumatic avulsion injuries, in which the globe was torn from the nerve, and certain gunshot wounds to the orbit that spared the globe completely, but in which the nerve was nevertheless shorn off. How an otherwise normal eye with good ocular motility could become separated completely from the optic nerve has generated much speculation over the years. Scores of cases have been reported in the literature, 2 but relatively few authors have offered any tangible explanation for the rupture of the optic nerve when the globe and its surrounding musculature remained relatively unscathed. “Extreme rotation” of the globe has been among the possible mechanisms implicated. 2 5 Recently, computer-assisted numerical modeling studies have indicated that the rate of globe rotation, facilitated by the resilient restraint offered by the retrobulbar fat pad, might be a more important factor than the angular extent of rotation as a basis for such shearing of the nerve. 6,7 Morris et al. 3 performed detailed histopathologic studies noting that in such injuries the optic nerves and their surrounding sheathes could be disrupted at two different locations, in two distinct combinations. Below are described findings that support this contention, and reaffirm the role of globe rotation (with or without associated intraorbital globe compression and rebound) in traumatic optic nerve neurapraxia and rupture. Indeed, provided impact is sufficiently tangential to the globe, rapid rotation alone may be sufficient to rupture the nerve adjacent to the lamina cribrosa via a strain rate mechanism. 
Methods
Paintball ocular impact and dynamic mechanical responses were studied for 59 porcine abattoir-obtained eyes struck under controlled conditions with paintballs in our ballistics laboratory (Fig. 1), as described thoroughly in Sponsel et al. 8 Briefly, impact experiments were conducted by launching paintball and solid rubber projectiles at mounted fresh porcine eye specimens. The eyes were prepared by carefully removing all remaining skin, eyelids, and fatty tissue to fully expose the ocular globe and optic nerve. All tenets of the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research were adhered to in the acquisition and postmortem use of these eyes. Each specimen was mounted in gelatin-filled (Knox; Kraft Foods, New York, NY) acrylic pyramidal-shaped holders that simulated the bony ocular orbit 9 (acrylic) and extraocular muscles (gelatin). Previous researchers have demonstrated that the extraocular muscles do not significantly influence the dynamic response of the eye during an impact event 9,10 ; thus, gelatin is commonly used in place of the muscles. 9,11 A catheter with attached saline-filled IV bag was inserted into the optic nerve to achieve the proper pretest hydrostatic pressure in the eye (∼18 mm Hg) and the eye assembly was placed in the center of the acrylic holder. All impacts were documented with a high-speed video camera (Phantom V-7; Vision Research, Inc., Wayne, NJ) with a mirror placed above the specimen and inclined at a 45° angle so as to obtain two orthogonal views with one camera. 
Figure 1.
 
Configuration of the transparent Perspex orbital mounts used in the porcine globe ballistic studies, allowing for high-speed bidirectional filming of the post-impact dynamic intraorbital distortion and displacement of each eye (see Sponsel et al. 8 for further details).
Figure 1.
 
Configuration of the transparent Perspex orbital mounts used in the porcine globe ballistic studies, allowing for high-speed bidirectional filming of the post-impact dynamic intraorbital distortion and displacement of each eye (see Sponsel et al. 8 for further details).
Two-tailed t-test comparisons of eyes sustaining direct central impact versus those sustaining a bidirectional video-confirmed glancing blow and subsequent ejection were performed. In parallel theoretical studies, the physics-based numerical code CTH, a Eulerian wave propagation code developed at Sandia National Laboratories, 12 was used, incorporating robust geometric and constitutive models of the eye and orbit. The results of direct impact on the globe, and corresponding models thereof, have been discussed previously. 8,13 16 Some eyes were uncharacteristically ejected anteriorly, and these formed the basis for this current analysis, using comparative parametric 3-D computational models of human eyes, defining physical characteristics of cornea, aqueous, lens, zonule, ciliary body, vitreous, sclera, and optic nerve. The slow motion representations of the impact and accompanying numerical modeling inform our conclusions on the mechanisms of optic nerve avulsion. 
Results
Among 59 porcine eye specimens submitted to paintball impact in the 1- to 13-J range, 10 (17%) disengaged completely from the firmly attached manometric probe and surrounding orbital gelatin mount (Table 1). The orientation of the optic nerve stalk within these mounts approximated the anatomic norm closely, since each globe was secured to a cannula passing through the Perspex orbital apex, and the anterior globe margin was centralized and appropriately positioned flush with the orbital rim. In each instance of globe expulsion, the paintball penetrated the orbit adjacent to the globe, producing rotation and eventual globe repulsion, dramatically evident on high-speed film images (Fig. 2). Because of this unique behavior, these eyes were excluded from the analysis of the effects of blunt direct ocular trauma published previously. 8 These expulsive events occurred on a regular basis, on multiple days throughout the test series, despite a uniform and highly standardized method for preparing the ballistic mounts. Clinically, traumatic transection of the optic nerve is rarely accompanied by complete globe evulsion, 2 since the suspensory ligaments, extraocular muscles, periorbita, lids, orbicularis muscle, and associated skin tend to retain the severely distracted globe. Nevertheless, within the confines of the orbit, substantial rotation and anteroposterior displacement of the globe can occur with minimal restraint from the extraocular musculature. 9 Thus, although the expulsion of relatively unrestrained, gelatin-mounted porcine eyes was not deemed to be representative of actual clinical pathology, the dramatic forces involved could not be reasonably overlooked. 
Table 1.
 
Summary of Globe Displacement and Deformation Data from Impact Experiments
Table 1.
 
Summary of Globe Displacement and Deformation Data from Impact Experiments
Test Hit Location Posterior Displacement (mm) Rebound Displacement (mm) Length Change (mm) Height Change (mm) Width Change (mm) Volume Change (%) Mean Diameter Change (mm)
1 CC-Hit 13.7 NR −6.2 3.1 0.2 −11.8 −1
2 CL-Hit 5.3 0.3 −5.4 1.1 4.1 −2.7 −0.1
3 TL-Miss 5.4 6.5 1 0.6 −2 −1.3 −0.1
4 BR-Miss 0 Ejected 0 −0.7 −0.8 −5.5 −0.5
5 CC-Hit 17.6 3.8 −6 0.1 2.2 −18.8 −1.2
6 BC-Hit 6.7 9.9 −3.8 −4.4 3.5 −19.2 −1.6
7 CC-Hit 10 9.9 −7.3 Rupture −1.6 0.7 −28.6 −2.7
8 CL-Hit 9.8 6.1 −2.8 1.5 1 −2.5 −0.1
9 BR-Hit 6.9 1.8 −2.4 −0.2 −0.2 −9.1 −0.9
10 BL-Miss 4.5 0.5 −1.7 −2.2 0 −16.2 −1.3
11 CC-Hit 4.9 4.7 −7.2 3.2 1.2 −15 −0.9
12 TC-Hit 3 5.2 −6.9 0.5 0 −28.5 −2.1
13 R-Miss 0.1 5.9 1.1 0.9 −4.9 −15.2 −1
14 BR-Miss 0.1 Ejected −0.4 −0.6 −1.6 −9.9 −0.8
15 TR-Miss 0.7 Ejected 0 −3 −0.6 −15.9 −1.2
16 CR-Hit 2.4 4.2 −2.1 3.5 −3 −8.2 −0.6
17 CR-Hit 7.6 1.1 −3.1 1.2 0 −7.8 −0.6
18 CC-Hit 5.4 NR −7.6 2.3 1.2 −18.1 −1.3
19 CC-Hit 4.9 NR −8.0 Rupture 3.6 1.9 −16 −0.9
20 CC-Hit 3.6 6.7 −4.1 0.8 2 −5.8 −0.4
21 TC-Hit 1.2 10.3 −0.3 −2.8 1.2 −7.6 −0.6
22 CC-Hit 1.2 4.3 −9.6 Rupture 0.6 2.6 −26.8 −2.1
23 CC-Hit 4.3 3 −6.3 4.3 0.4 −8.7 −0.5
24 CC-Hit 4.3 4.3 −8.1 0.8 1.7 −20.6 −1.8
25 BL-Miss 0.6 Ejected −2.1 1.4 0.6 −0.8 −0.1
26 TL-Miss 0.3 3.9 −0.7 −2.4 −2 −17.2 −1.7
27 CC-Hit 1.3 8.3 −8.1 Rupture 1.2 1.2 −22.8 −1.9
28 CL-Hit 0.2 5 −4.4 4.9 −3.3 −11.9 −0.9
29 TR-Miss 0.5 Ejected −0.6 −0.1 −2.6 −12.1 −1.1
31 BC-Hit 1.3 11 −6.9 0.5 1.4 −19.5 −1.7
32 CC-Hit 5.2 9.1 −8.2 2.2 2 −18 −1.4
33 CC-hit 2 2.6 −7.5 2.9 0 −17.7 −1.5
34 CL-Hit 1.9 12.2 −10.6 3.3 3.6 −23.1 −1.2
35 BR-Miss 0 16.3 0.6 −6.7 0.6 −20.8 −1.8
36 CR-Hit 3.3 7.8 −6 0.5 0 −19 −1.8
37 CC-Hit 4.4 2.6 −2.4 −0.6 −0.1 −11.6 −1
38 CC-Hit 2.6 5.1 −5.3 2.4 0.1 −12.1 −0.9
39 TC-Hit 2.5 5 −5 −0.8 1.1 −17.1 −1.6
40 CC-Hit 1.9 5.7 −7.7 1.3 1.7 −17.6 −1.6
41 CC-Hit 5.3 6.4 −3 0.5 0.2 −8.6 −0.7
42 CC-Hit 2.7 2 −4.9 0.6 1.3 −11.5 −1
43 BR-Miss 2.1 Ejected −0.6 −4.8 1 −18 −1.4
44 CC-Hit 4.1 7.6 −9.2 Rupture 0.6 2.5 −30.5 −2
45 CL-Hit 4.1 Ejected −3.1 1.8 0.6 −4.1 −0.2
46 CC-Hit 4.6 4.1 −5.1 2 2.2 −7.6 −0.3
47 TC-Hit 5.6 Ejected −7.1 1.7 3.2 −13.5 −0.7
48 BL-Miss 1 Ejected −5.1 0.9 1.8 −12.2 −0.8
49 CC-Hit 1.6 5.7 −7.8 Rupture 2.5 1.7 −15.9 −1.2
50 CC-Hit 3 7.1 −6 1.3 2.2 −10.5 −0.8
51 CC-Hit 4 4.6 −3.3 0.2 0.6 −9.6 −0.8
52 CC-Hit 3.6 2 −7.1 0.4 1.1 −20.2 −1.9
53 TL-Hit 2.1 11.3 −5.8 0.5 1 −16.5 −1.4
54 BL-Miss 0.2 15 −2.3 −2.6 2.3 −10.3 −0.9
55 CL-Hit 2.1 10.8 −2.7 0.6 0.3 −6.6 −0.6
56 CC-Hit 3 2.6 −4.1 0.7 0.9 −9.8 −0.8
57 TR-Miss 0.5 2 −3.1 −1.1 1.7 −9.7 −0.8
58 CC-Hit 4.2 10.9 −5.3 1 0.5 −14.4 −1.2
59 BL-Miss 1 Ejected −4.9 1.2 0.1 −12.9 −1.2
Figure 2.
 
Concurrent time sampling views of the effects of a 20-mm offset impact as depicted by CTH numerical modeling (top) and empirical high-speed ballistic testing (bottom). Note the minimal posterior displacement and distortion of the eye in the middle panels, even as the paint loculus advances beyond the globe's equator.
Figure 2.
 
Concurrent time sampling views of the effects of a 20-mm offset impact as depicted by CTH numerical modeling (top) and empirical high-speed ballistic testing (bottom). Note the minimal posterior displacement and distortion of the eye in the middle panels, even as the paint loculus advances beyond the globe's equator.
To better understand the nature of this less common but experimentally frequent phenomenon, supercomputer modeling was performed with CTH, programmed with 10-mm off-center, oblique impact and with 20-mm tangential impact, with the paintball speed set at 300 m/s. Globe-expulsive events were observed when the paintball impact was sufficiently offset from the globe center and when pyramidal bony orbital constraints were in place, but not when these were removed. Twenty-millimeter tangentially offset (grazing) impact sheared the nerve flush with the globe via a strain rate effect within 260 μs, with minimal posterior displacement and just 5° of globe rotation (Fig. 3; top series). Ten-millimeter offset midperipheral impact produced compressive globe distortion and posterior displacement, followed by rebound and tractional nerve avulsion 10 mm behind the lamina, after 700 μs and 20° of globe rotation (Fig. 3; bottom series). 
Figure 3.
 
Time sampling views of CTH modeling showing dynamic pressure changes within the globe and orbit accompanying a 300 ms−1 paintball impact. Top: the effects of a 20-mm offset impact; bottom: a 10-mm offset impact. Note the differences in posterior displacement, rotation and rebound of the globe, and the elapsed time and location of optic nerve rupture. Using average mechanical properties for the dura (Duck 26 ), the CTH model predicted a 0.28 strain value in the optic nerve during rupture.
Figure 3.
 
Time sampling views of CTH modeling showing dynamic pressure changes within the globe and orbit accompanying a 300 ms−1 paintball impact. Top: the effects of a 20-mm offset impact; bottom: a 10-mm offset impact. Note the differences in posterior displacement, rotation and rebound of the globe, and the elapsed time and location of optic nerve rupture. Using average mechanical properties for the dura (Duck 26 ), the CTH model predicted a 0.28 strain value in the optic nerve during rupture.
Impact thresholds for various clinically relevant forms of intraocular injury have been detailed previously. 8 In 10 eyes that underwent total avulsion from the orbit, the paintball had entered the orbit adjacent to the globe, forcefully propelling the globe anteriorly once the loculated paint mass proceeded posteriorly beyond the equator of the globe. The speed and force of this “ricochet repulsion” was dramatically evident on high-speed film images. 
Supercomputer modeling experiments produced comparable results when orbital constraints were in place, but not when these were removed. Using CTH, The 300-ft/s, 10- and 20-mm offset impacts were run to simulate the ballistic experiments wherein the paintball ejected the eye (Fig. 4 showing a 2-D plane cut through the center of the eye and acrylic holder to allow for viewing into the interior of the simulated orbit). The predictions of the numerical models appear to be borne out in the statistical analysis of the associations of impact location and globe displacement in the empirical porcine ballistic studies. Table 1 shows the ocular distortion and intraorbital globe displacement and rebound data for the 59 eyes submitted to paintball trauma. The energy and histopathologic data for these impact studies have been presented previously. 8 Posterior intraorbital displacement (measured from the optic nerve head) was 4.76 ± 0.76 mm (SEM) for the 26 eyes sustaining direct central impact, three times higher than that observed among the ten ejected globes (1.57 ± 0.59 mm; P = 0.016). Of some interest was the difference in posterior displacement of the ejected globes documented as having sustained an offset “hit” as opposed to a “miss” (4.85 ±0.75 vs. 0.75 ± 0.23; P < 0.0001), indicating the likelihood of different mechanisms of nerve disengagement such as that suggested by the numerical modeling exercises. The maximum change in axial length of the globes during impact was correspondingly different, with those sustaining central impact shortening by 6.4 ± 0.38 mm, while ejected offset–miss globes shortened by only 0.9 ± 0.7 mm (P < 0.0001). Further comparisons of this kind may be readily performed incorporating the energy and pathologic data published previously, reaffirming that eyes likely to sustain the greatest rotational or rebound traction trauma to the optic nerve were often those demonstrating the least intraocular pathology. 
Figure 4.
 
Cutaway view demonstrating sequential axial and coronal distortions of the globe and its early lateral movement (1, 2), and subsequent forward displacement (3, 4) as the retrobulbar contents are displaced by the ethylene glycol paint loculus.
Figure 4.
 
Cutaway view demonstrating sequential axial and coronal distortions of the globe and its early lateral movement (1, 2), and subsequent forward displacement (3, 4) as the retrobulbar contents are displaced by the ethylene glycol paint loculus.
Discussion
The original purpose of this series of ballistic studies was to characterize the histopathologic damage caused by direct impact of paintballs at various velocities. We have described in detail the energy associations with direct anteroposterior impact forces on the porcine eye, 8 and the related changes predicted for similar injuries in a numerical model of the orbitally constrained human eye. 17 Others have performed important recent studies evaluating the effects of various sources of impact on biological and model human eyes. 18 22  
The ejection of the globes from the acrylic holders in the present study was an incidental finding of one of the studies cited above. 8 This triggered further evaluation, not of the globe distraction, per se, but of the likely effect of the forces involved on the optic nerve. It is important to note that forces that can rupture a human globe may merely rotate a porcine eye, 23,24 so the forces relevant to humans for the unique mechanism of injury described below may be lower than those described herein, should actual rupture preclude rotation. Notwithstanding this qualifying comment, and consistent with prior clinical observations, computer models run with human-derived variables identified two different patterns of damage to the optic nerve. Tangential impact produced a nerve-breaching point proximal to the globe via a different mechanism than was generated with a midperipheral hit, which breached the nerve in the midintraorbital region. Approximations of these two discrete mechanisms were first postulated by Morris et al. in 2002, 3 and these appear to have been confirmed with the models. The length of the optic nerve segment remaining connected to the globe appears to a function of the degree of decentration of the impact, speed of ocular rotation, extent of early posterior displacement of the globe within the orbit, and the subsequent anterograde rebound of the eye after impact. 
Anatomically the approach to the eye that would appear to create the greatest risk of such injury would be inferiorly and temporally adjacent to the zygoma, where the globe is most exposed both laterally and axially. The opposing rigid superior orbital wall would tend to provide a more unyielding vectus for axial globe compression than either the nasally situated ethmoid air cells or the inferior lamina papyracea, minimizing any prospect for inferior blowout fracture allowing migration of the globe into the maxillary sinus to mitigate ocular injury. This is of particular interest, since many forms of popular protective eyewear actually feature a fashionable inferotemporal “batwing” cut that fully exposes the inferotemporal globe to impacts that could readily produce rotational optic nerve avulsion, or rebound rotational evulsion, even at relatively low-impact velocities (like the orbital penetrating finger model used in the studies of Cirovic et al. 6,7 ). 
Because of the probability of concomitant severe ocular injury initially obscuring observation of the posterior pole and because the optic nerve head remains avascular but intact, the actual incidence of total rebound evulsion among eyes blinded by blunt trauma may be much higher than has been documented hitherto. More important, the extent of pathologic neurapraxia producing lifelong visual compromise in instances of subtotal evulsion or avulsion (see typical postimpact peripapillary histopathologic section shown in Fig. 9 in Sponsel et al. 8 ) is unknown, but may also be reasonably expected to exist at levels much higher than have been identified clinically. Individuals with such subtotal injury are of particular concern, because incompletely severed nerves with the optic sheath intact may benefit from timely therapy, including but not limited to systemic administration of corticosteroids or surgical decompression. Such treatment might plausibly salvage many axons that might otherwise undergo apoptosis or necrosis. We would thus advocate, where available, the use of high-resolution orbital imaging to rule out the possibility of distal intraorbital nerve injury whenever the possibility of rotational ocular injury is suspected. The unique risks posed by inferior and temporal ocular exposure to rotation-inducing blunt impact should also be taken into account in the future design of protective eyewear. 25  
Footnotes
 Presented in part at the annual meeting of the Association for Research in Vision and Ophthalmology, Fort Lauderdale, Florida, May 2009.
Footnotes
 Supported by Southwest Research Institute IR&D Grant R9664.
Footnotes
 Disclosure: W.E. Sponsel, None; W. Gray, None; S.L. Groth, None; A.R. Stern, None; J.D. Walker, None
References
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Figure 1.
 
Configuration of the transparent Perspex orbital mounts used in the porcine globe ballistic studies, allowing for high-speed bidirectional filming of the post-impact dynamic intraorbital distortion and displacement of each eye (see Sponsel et al. 8 for further details).
Figure 1.
 
Configuration of the transparent Perspex orbital mounts used in the porcine globe ballistic studies, allowing for high-speed bidirectional filming of the post-impact dynamic intraorbital distortion and displacement of each eye (see Sponsel et al. 8 for further details).
Figure 2.
 
Concurrent time sampling views of the effects of a 20-mm offset impact as depicted by CTH numerical modeling (top) and empirical high-speed ballistic testing (bottom). Note the minimal posterior displacement and distortion of the eye in the middle panels, even as the paint loculus advances beyond the globe's equator.
Figure 2.
 
Concurrent time sampling views of the effects of a 20-mm offset impact as depicted by CTH numerical modeling (top) and empirical high-speed ballistic testing (bottom). Note the minimal posterior displacement and distortion of the eye in the middle panels, even as the paint loculus advances beyond the globe's equator.
Figure 3.
 
Time sampling views of CTH modeling showing dynamic pressure changes within the globe and orbit accompanying a 300 ms−1 paintball impact. Top: the effects of a 20-mm offset impact; bottom: a 10-mm offset impact. Note the differences in posterior displacement, rotation and rebound of the globe, and the elapsed time and location of optic nerve rupture. Using average mechanical properties for the dura (Duck 26 ), the CTH model predicted a 0.28 strain value in the optic nerve during rupture.
Figure 3.
 
Time sampling views of CTH modeling showing dynamic pressure changes within the globe and orbit accompanying a 300 ms−1 paintball impact. Top: the effects of a 20-mm offset impact; bottom: a 10-mm offset impact. Note the differences in posterior displacement, rotation and rebound of the globe, and the elapsed time and location of optic nerve rupture. Using average mechanical properties for the dura (Duck 26 ), the CTH model predicted a 0.28 strain value in the optic nerve during rupture.
Figure 4.
 
Cutaway view demonstrating sequential axial and coronal distortions of the globe and its early lateral movement (1, 2), and subsequent forward displacement (3, 4) as the retrobulbar contents are displaced by the ethylene glycol paint loculus.
Figure 4.
 
Cutaway view demonstrating sequential axial and coronal distortions of the globe and its early lateral movement (1, 2), and subsequent forward displacement (3, 4) as the retrobulbar contents are displaced by the ethylene glycol paint loculus.
Table 1.
 
Summary of Globe Displacement and Deformation Data from Impact Experiments
Table 1.
 
Summary of Globe Displacement and Deformation Data from Impact Experiments
Test Hit Location Posterior Displacement (mm) Rebound Displacement (mm) Length Change (mm) Height Change (mm) Width Change (mm) Volume Change (%) Mean Diameter Change (mm)
1 CC-Hit 13.7 NR −6.2 3.1 0.2 −11.8 −1
2 CL-Hit 5.3 0.3 −5.4 1.1 4.1 −2.7 −0.1
3 TL-Miss 5.4 6.5 1 0.6 −2 −1.3 −0.1
4 BR-Miss 0 Ejected 0 −0.7 −0.8 −5.5 −0.5
5 CC-Hit 17.6 3.8 −6 0.1 2.2 −18.8 −1.2
6 BC-Hit 6.7 9.9 −3.8 −4.4 3.5 −19.2 −1.6
7 CC-Hit 10 9.9 −7.3 Rupture −1.6 0.7 −28.6 −2.7
8 CL-Hit 9.8 6.1 −2.8 1.5 1 −2.5 −0.1
9 BR-Hit 6.9 1.8 −2.4 −0.2 −0.2 −9.1 −0.9
10 BL-Miss 4.5 0.5 −1.7 −2.2 0 −16.2 −1.3
11 CC-Hit 4.9 4.7 −7.2 3.2 1.2 −15 −0.9
12 TC-Hit 3 5.2 −6.9 0.5 0 −28.5 −2.1
13 R-Miss 0.1 5.9 1.1 0.9 −4.9 −15.2 −1
14 BR-Miss 0.1 Ejected −0.4 −0.6 −1.6 −9.9 −0.8
15 TR-Miss 0.7 Ejected 0 −3 −0.6 −15.9 −1.2
16 CR-Hit 2.4 4.2 −2.1 3.5 −3 −8.2 −0.6
17 CR-Hit 7.6 1.1 −3.1 1.2 0 −7.8 −0.6
18 CC-Hit 5.4 NR −7.6 2.3 1.2 −18.1 −1.3
19 CC-Hit 4.9 NR −8.0 Rupture 3.6 1.9 −16 −0.9
20 CC-Hit 3.6 6.7 −4.1 0.8 2 −5.8 −0.4
21 TC-Hit 1.2 10.3 −0.3 −2.8 1.2 −7.6 −0.6
22 CC-Hit 1.2 4.3 −9.6 Rupture 0.6 2.6 −26.8 −2.1
23 CC-Hit 4.3 3 −6.3 4.3 0.4 −8.7 −0.5
24 CC-Hit 4.3 4.3 −8.1 0.8 1.7 −20.6 −1.8
25 BL-Miss 0.6 Ejected −2.1 1.4 0.6 −0.8 −0.1
26 TL-Miss 0.3 3.9 −0.7 −2.4 −2 −17.2 −1.7
27 CC-Hit 1.3 8.3 −8.1 Rupture 1.2 1.2 −22.8 −1.9
28 CL-Hit 0.2 5 −4.4 4.9 −3.3 −11.9 −0.9
29 TR-Miss 0.5 Ejected −0.6 −0.1 −2.6 −12.1 −1.1
31 BC-Hit 1.3 11 −6.9 0.5 1.4 −19.5 −1.7
32 CC-Hit 5.2 9.1 −8.2 2.2 2 −18 −1.4
33 CC-hit 2 2.6 −7.5 2.9 0 −17.7 −1.5
34 CL-Hit 1.9 12.2 −10.6 3.3 3.6 −23.1 −1.2
35 BR-Miss 0 16.3 0.6 −6.7 0.6 −20.8 −1.8
36 CR-Hit 3.3 7.8 −6 0.5 0 −19 −1.8
37 CC-Hit 4.4 2.6 −2.4 −0.6 −0.1 −11.6 −1
38 CC-Hit 2.6 5.1 −5.3 2.4 0.1 −12.1 −0.9
39 TC-Hit 2.5 5 −5 −0.8 1.1 −17.1 −1.6
40 CC-Hit 1.9 5.7 −7.7 1.3 1.7 −17.6 −1.6
41 CC-Hit 5.3 6.4 −3 0.5 0.2 −8.6 −0.7
42 CC-Hit 2.7 2 −4.9 0.6 1.3 −11.5 −1
43 BR-Miss 2.1 Ejected −0.6 −4.8 1 −18 −1.4
44 CC-Hit 4.1 7.6 −9.2 Rupture 0.6 2.5 −30.5 −2
45 CL-Hit 4.1 Ejected −3.1 1.8 0.6 −4.1 −0.2
46 CC-Hit 4.6 4.1 −5.1 2 2.2 −7.6 −0.3
47 TC-Hit 5.6 Ejected −7.1 1.7 3.2 −13.5 −0.7
48 BL-Miss 1 Ejected −5.1 0.9 1.8 −12.2 −0.8
49 CC-Hit 1.6 5.7 −7.8 Rupture 2.5 1.7 −15.9 −1.2
50 CC-Hit 3 7.1 −6 1.3 2.2 −10.5 −0.8
51 CC-Hit 4 4.6 −3.3 0.2 0.6 −9.6 −0.8
52 CC-Hit 3.6 2 −7.1 0.4 1.1 −20.2 −1.9
53 TL-Hit 2.1 11.3 −5.8 0.5 1 −16.5 −1.4
54 BL-Miss 0.2 15 −2.3 −2.6 2.3 −10.3 −0.9
55 CL-Hit 2.1 10.8 −2.7 0.6 0.3 −6.6 −0.6
56 CC-Hit 3 2.6 −4.1 0.7 0.9 −9.8 −0.8
57 TR-Miss 0.5 2 −3.1 −1.1 1.7 −9.7 −0.8
58 CC-Hit 4.2 10.9 −5.3 1 0.5 −14.4 −1.2
59 BL-Miss 1 Ejected −4.9 1.2 0.1 −12.9 −1.2
×
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