An intraocular pressure measurement technique for eye impact testing - biomed 2010

Eye injuries remain a large societal problem in both the military and civilian sectors. Eye injury rates are increasing in recent military conflicts and there are over 1.9 million eye injuries in the United States civilian sector annually. In order to develop a better understanding of eye injury risk, several previous studies have developed eye injury criteria based on projectile characteristics. While these injury criteria have been used to estimate eye injury potential of blunt impact scenarios, they require that the mass, size and velocity of the projectile are known. It is desirable to develop a method to assess the severity of an eye impact in environments where it would be difficult or impossible to determine these projectile characteristics. The current study presents a measurement technique for monitoring intraocular pressure of the eye under impact. Through experimental tests with a custom pressure chamber, a subminiature pressure transducer was validated to be thermally stable and suitable for testing in an impact environment. Once validated, the transducer was utilized intraocularly, inserted through the optic nerve, to measure the pressure of the eye during blunt-projectile impacts. A total of 24 impact tests were performed using projectiles ranging from 6.3 mm to 9.5 mm in diameter. A correlation coefficient, R, of 0.95 indicates that intraocular pressure is correlated to the projectile mass-, size-, and velocity-based parameter of normalized energy. Further testing should be performed to better develop injury criteria based on intraocular pressure and to investigate the relationship between pressure- and projectile-based injury criteria. Intraocular pressure measurements also indicated a different response for perforating-type open-globe injuries with smaller diameter projectiles and scleral-rupture open-globe injuries with larger diameter projectiles. This indicates that intraocular pressure may lead to a better understanding of the transition between penetrating- and rupture-type injury mechanisms.