Vanessa D. Alphonse

Mechanisms of eye injuries from fireworks

Injuries from fireworks are prevalent among youth. The eye is the most frequently injured body part and accounts for more than 2000 injuries annually. Although it is suggested the pressure wave caused by explosions (i.e. blast overpressure) can cause serious eye injuries, there is no clear evidence to support this. The purpose of this research is to assess whether blast overpressure or projected material from fireworks causes eye injury. This study evaluates the response of six human cadaver eyes to charges at distances of 22 cm, 12 cm, and 7 cm from the cornea. Due to variability in consumer fireworks, 10 g charges of Pyrodex gunpowder were used to simulate fireworks in a controlled, repeatable manner. A pressure sensor inserted in the vitreous measured intraocular pressure, and four pressure sensors mounted around the eye measured total and static pressures. Pressure measurements were used to calculate rise time, positive duration, impulse, and wave velocity. The charges produced survivable peak overpressures (Average maximum pressure = 51.15 kPa) which correspond to detonating 0.45 kg TNT at approximately 3.0 m. Minor grain-sized corneal abrasions were the only injuries observed. The abrasion size and pattern suggested unspent gunpowder was projected onto the eye, which was confirmed with high speed video. Increasing proximity to the eye resulted in more abrasions. Intraocular pressure was used to calculate injury risk, which was less than or equal to 0.01% for hyphema, lens damage, retinal damage, and globe rupture. The low calculated injury risk further supports the lack of major injuries observed. The combined presence of injuries caused by projected material and lack of injuries directly caused by the blast overpressure indicated serious eye injuries could be caused by projectiles, but not blast overpressure, at these energy levels.

Eye Injury Risk from Water Stream Impact: Biomechanically Based Design Parameters for Water Toy and Park Design

Purpose: Interactive water displays are becoming increasingly popular and can result in direct eye contact. Therefore, the purpose of this study is to investigate eye injury risk from high speed water stream impacts and to provide biomechanically based design parameters for water toys and water park fountains. Methods: An experimental matrix of 38 tests was developed to impact eight porcine eyes with water streams using a customized pressure system. Two stream diameters (3.2 mm and 6.4 mm) were tested at water velocities between 3.0 m/s and 8.5 m/s. Intraocular pressure was measured with a small pressure sensor inserted through the optic nerve and used to determine the injury risk for hyphema, lens dislocation, retinal damage, and globe rupture for each impact. Results: Experimental water stream impacts created a range of intraocular pressures between 3156 mmHg and 7006 mmHg (61 psi to 135 psi). Injury risk varied between 4.4%–27.8% for hyphema, 0.0%–3.0% for lens dislocation, and 0.1%–3.3% for retinal damage. All tests resulted in 0.0% injury risk for globe rupture. The two water stream diameters did not result in significantly different water stream velocities (P = 0.32); however, the variation in water stream diameter did result in significantly different intraocular pressures (P = 0.03) with higher pressures for the 6.4 mm stream. Conclusions: This is the first study to experimentally measure intraocular pressure from high speed water stream impacts and quantify the corresponding eye injury risk. It is recommended that toy water guns and water park fountains use an upper threshold of 8.5 m/s for water stream velocities to minimize the risk of serious acute eye damage from impacts.

Blast simulator considerations for testing symmetrical specimens

An increasing number of studies use blast simulators to assess blast exposure as a potential mechanism for traumatic brain injury, post-traumatic stress disorder, and tissue damage to the eye and ear. However, the small diameter of many blast simulators limits specimen size, and it is often not feasible to test a full-scale dummy or cadaver head. It has been suggested that a plane of symmetry could be used to model realistic boundary conditions for a smaller portion of a symmetrical object. Therefore, test fixtures that occluded either 10% or 20% of the cross-sectional area of the tube were tested with and without a plane of symmetry to assess the effect of object size and the plane of symmetry. Static pressure along the tube wall and reflected pressure on the surface of the fixture were measured. Each test was conducted in duplicate at 70 kPa, 140 kPa, and 210 kPa to simulate survivable, but increasingly severe blasts. Tests with the plane of symmetry produced pressure traces that more accurately simulated idealized Friedlander waveforms. Peak overpressure and positive duration were similar in magnitude for both the 10% and 20% occlusion fixtures when the plane of symmetry was used. Future studies using blast simulators to test large, symmetrical specimens such as the human head should consider using a POS and limiting occluded area to <;20% to accurately model the in vivo response to blast overpressure.

Human Eye Response to Blast Overpressure

Each year, approximately two million people in the United States suffer eye injuries that require treatment [1]. Although it is suggested that blast overpressure can cause serious eye injuries, there is no clear evidence in the literature to support this injury mechanism. Conversely, projectile impacts have been shown to cause serious eye injuries [2, 3]. The critical question is whether blast overpressure alone can cause eye injury or if injuries are caused solely by projected material. Therefore, the purpose of the current study is to measure the intraocular pressure (IOP) of postmortem human eyes during blasts and assess injuries sustained in order to more fully understand the effect of blast overpressure on the eye.Copyright

Evaluating the Risk of Eye Injuries: Intraocular Pressure During High Speed Projectile Impacts

In order to predict and possibly prevent ocular injuries for various impact scenarios, previous research investigated injuries from projectile impacts with known characteristics. Normalized energy was determined as the most significant predictor of injury type and tissue lesion. Although studies have reported the injury risk for projectile impacts to the globe, none have reported the corresponding intraocular pressure [1]. Quantifying intraocular pressure during impacts may provide insight to vision problems such as glaucoma and cataracts. Therefore, the purpose of the current study is to determine intraocular pressure during high speed projectile impacts to eyes.Copyright