A Case of Air-bag Associated Severe Ocular Injury

Simulation of Changes in Tensile Strain by Airbag Impact on Eyes After Trabeculectomy by Using Finite Element Analysis

Purpose

We studied the kinetic phenomenon of an airbag impact on eyes after trabeculectomy using finite element analysis (FEA), a computerized method for predicting how an object reacts to real-world physical effects and showing whether an object will break, to sequentially determine the responses at various airbag deployment velocities.

Methods

A human eye model was used in the simulations using the FEA program PAM-GENERISTM (Nihon ESI, Tokyo, Japan). A half-thickness incised scleral flap was created on the limbus and the strength of its adhesion to the outer sclera was set at 30%, 50%, and 100%. The airbag was set to hit the surface of the post-trabeculectomy eye at various velocities in two directions: perpendicular to the corneal center or perpendicular to the scleral flap (30° gaze-down position), at initial velocities of 20, 30, 40, 50, and 60 m/s.

Results

When the airbag impacted at 20 m/s or 30 m/s, the strain on the cornea and sclera did not reach the mechanical threshold and globe rupture was not observed. Scleral flap lacerations were observed at 40 m/s or more in any eye position, and scleral rupture extending posteriorly from the scleral flap edge and rupture of the scleral flap resulting from extension of the corneal laceration through limbal damage were observed. Even in the case of 100% scleral flap adhesion strength, scleral flap rupture occurred at 50 m/s impact velocity in the 30° gaze-down position, whereas in eyes with 30% or 50% scleral flap adhesion strength, scleral rupture was observed at an impact velocity of 40 m/s or more in both eye positions.

Conclusion

An airbag impact of ≥40 m/s might induce scleral flap rupture, indicating that current airbags may induce globe rupture in the eyes after trabeculectomy. The considerable damage caused by an airbag on the eyes of short-stature patients with glaucoma who have undergone trabeculectomy might indicate the necessity of ocular protection to avoid permanent eye damage.

Finite Element Analysis of Changes in Deformation of Intraocular Segments by Airbag Impact in Eyes of Various Axial Lengths

Background

We studied the kinetic phenomenon of an airbag impact on eyes with different axial lengths using finite element analysis (FEA) to sequentially determine the physical and mechanical responses of intraocular segments at various airbag deployment velocities.

Methods

The human eye model we created was used in simulations with the FEA program PAM-GENERISTM. The airbag was set to impact eyes with axial lengths of 21.85 mm (hyperopia), 23.85 mm (emmetropia) and 25.85 mm (myopia), at initial velocities of 20, 30, 40, 50 and 60 m/s. The deformation rate was calculated as the ratio of the length of three segments, anterior chamber, lens and vitreous, to that at the baseline from 0.2 ms to 2.0 ms after the airbag impact.

Results

Deformation rate of the anterior chamber was greater than that of other segments, especially in the early phase, 0.2-0.4 ms after the impact (P < 0.001), and it reached its peak, 80%, at 0.8 ms. A higher deformation rate in the anterior chamber was found in hyperopia compared with other axial length eyes in the first half period, 0.2-0.8 ms, followed by the rate in emmetropia (P < 0.001). The lens deformation rate was low, its peak ranging from 40% to 75%, and exceeded that of the anterior chamber at 1.4 ms and 1.6 ms after the impact (P < 0.01). The vitreous deformation rate was lower throughout the simulation period than that of the other segments and ranged from a negative value (elongation) in the later phase.

Conclusion

Airbag impact on the eyeball causes evident deformation, especially in the anterior chamber. The results obtained in this study, such as the time lag of the peak deformation between the anterior chamber and lens, suggest a clue to the pathophysiological mechanism of airbag ocular injury.

Car Accident With Airbag Deployment Trauma Showed Special Pattern in Bone Scan

A 72-year-old man had rectal adenocarcinoma with partial obstruction with liver and lung metastases. Bone scan showed special pattern with bony destructions to the lateral aspect of the left first to fourth and right first to 10th ribs (in a row in continuous vertical alignment), the costal end of the left second rib, the left sternoclavicular junction, and sternum. Patient recalled a car traffic accident with airbag deployment trauma to the anterior aspect of the chest about 2 months prior. Chest CT confirmed that the bone lesions were all fractures.

Airbag induced facial and bilateral ocular injuries in a 14-year-old child

Although air bags have reduced the incidence of fatal and severe injuries in automobile collisions, they have been shown to carry a risk of injury themselves. Ocular injury in particular can often be a direct consequence of air bag deployment. We report a 14-year-old child who sustained facial burn and bilateral ocular injuries affecting both the anterior and posterior segments due to an inflated air bag in a low speed motor vehicle accident.