Deformation of the globe under high-speed impact: Its relation to contusion injuries F. Delori, O. Pomerantzeff, and M. S. Cox* Enucleated pig eyes in 10 per cent gelatin were submitted to nonperforating injury in order to record and measure the deformations of the eye and explain the mechanism of damage at the vitreous base. High-speed motion pictures and single flash high-speed photographs were used for this purpose. The general theory of the central impact of two bodies was correlated with previous and present experiments. Reconstruction of the motion was based on the con- stancy of the mass of the globe and on the experimental data obtained. This reconstruction was used to determine local accelerations of the ocular coats, distension of the walls, energetic balance and magnitude of the forces involved. A theory was proposed to explain the damage observed at the vitreous base. Key words: vitreous base, photography, pigs, enucleation, mathematical analysis, eyeball contusion, lens capsule, ora serrata, pars plana ciliaris. D,amage to the peripheral retina and tography and cinematography, the very pars plana ciliaris from nonperforating rapid deformations of the globe caused by trauma of the eye often results in retinal the projectile and the mechanism by which breaks along the border of the vitreous damage was produced to the ocular tissues. base: dialysis along the posterior border and linear breaks in the epithelium of the Materials and methods pars plana ciliaris along the anterior bor- Eyes and molds. The pig eye was chosen by der.1 Weindenthal and Schepens2 dupli- Weidenthal because of its similarity to the human eye in the area of the ora serrata and pars plana cated these breaks by traumatizing enucle- ciliaris. Pig eyes were enucleated and traumatized ated pig eyes, mounted in gelatin, with an within 2 to 4 hours after the animal's death. air rifle projectile. They demonstrated ex- Each eye was mounted in a separate gelatin perimentally that equatorial expansion of mold consisting of a 5 by 5 by 8 cm. container the globe under impact is partially respon- made with flat glass plates. The eye was suspended in the container by threads, and liquid 10 per cent sible for the damage. With Weidenthal's gelatin at a temperature of 30° to 40° C. was model we investigated, by high-speed pho- poured in the container leaving the anterior part of the eye exposed (Fig. 1). The liquid gelatin was then allowed to gel. From the Department of Retina Research, Institute In order to study the stretching of the ocular of Biological and Medical Sciences, Retina coats, fine black threads were sutured to the sclera Foundation, Boston, Mass. and small knots made in it as reference points. This work was supported by a Public Health Changes in the length of the globe's axis were Service Research Grant B 3489 of the National measured with reference to the dimensions of the Institute of Neurological Diseases and Blind- axes before impact. ness, United States Public Health Service. Mounted in gelatin, the eyes had a pressure Manuscript submitted May 9, 1968; revised manu- varying between 15 and 20 scale readings with a Schi0tz tonometer. The normal reading in vivo script accepted July 11, 1968. was about 5 scale readings." No attempt was made * Special Fellow of the National Institute of Neuro- logical Diseases and Blindness, United States "Readings were relative on pig eyes since the Schi0tz Public Health Service (NB 1368). tonometer is designed for the human eye. 290 Downloaded from iovs.arvojournals.org on 09/28/2021 Volume 8 Globe deformation under high-speed impact 291 Number 3 1. Enucleated Eye the cornea with the missile path. The disadvantage 2. 10% Gelatin of this type of mounting was a small deformation 3. Gun of the cornea before impact due to the air blast. 4. Contact Assembly Photographic recordings. Photographic record- 5. Glass Mold ings consisted of high-speed single flash photogra- 6. Steel BB phy and cinematography. In single flash high- 7. Magnesium Missile speed photography4 (Fig. 2), the object was illuminated during a very short time so that all motion seemed to have "stopped" on the photo- graph. The experiment took place in complete darkness. The camera, focused on the eye, was opened for one second during which the gun was fired. When the bullet left the gun, it closed momentarily a pair of electrical contacts consisting of 0.0015 inch steel blades. A resulting voltage pulse was sent through an adjustable delay line" to an electronic flash unit,f which produced a Fig. 1. Enucleated pig eye mounted in 10 per short but powerful flash of light. The exposure cent gelatin in a glass mold. The muzzle of the time was thus equal to the length of the light air rifle with its contact assembly is shown to the pulse (3 Msec), and the intensity of the flash was right. The insert illustrates the two types of mis- about 7 million beam candlepower. The light flash siles used. was intentionally produced between 0.1 and 10 msec, after the voltage pulse depending on the to normalize the intraocular pressure of the enucle- phase of motion to be photographed. The delay ated eyes. Fluid injected into the intraocular cav- was preset and measured for each exposure with ity might have escaped from the globe through the a cathode ray oscilloscope. The use of direct de- needle track during impact. Any method of in- velopment film with high sensitivity! made the creasing the pressure externally would have limited procedure very versatile. This technique would movements of the globe during impact. Since have been inefficient if only one picture per eye damage to ocular tissues, observed under these could have been taken. The deformations of the conditions, was similar to that observed when the globe under repetitive impact were so similar that globe was left in situ,1 it did not seem important no changes greater than the experimental error to normalize the pressure. could be detected. This permitted the use of the same eye for repeated impacts and photographs. Two human eyes were used which had been However, no measurements of eyes after the fifth enucleated 12 and 24 hours before the experi- impact were taken into account. Pictures of the ment. The donor" was a 24-year-old woman undistorted eye were taken before and after a whose eyes had been removed 4 hours after death series of impacts. A total of 213 single flash pic- from uremia. tures of pig eyes were taken. Missiles. The ocular injury was produced by a specially modified air riflef which fired a standard With high-speed cinematography (Fig. 3) the projectile called a BB (0.345 gr.) at an average object to be photographed was continuously illumi- speed of 62.3 M. per second (±2.5 per cent). This nated, and the film was exposed during very speed was selected to insure a nonpenetrating short times by a fast shutter. The camera^ was trauma of the cornea since it had been established driven by a motor at speeds between 5,000 and that penetrating injury occurred at speeds higher 3 9,000 frames per second. Some time was required than 72.0 M. per second. It was necessary to use before the film reached the desired speed, then a magnesium projectile, of greater length but the gun was fired by a pair of solenoids actuated identical speed and weight as the steel BB, to by an event synchronizer inside the camera. A 60 measure the depth of the corneal indentation dur- cycle per second flashing light was incorporated ing impact because this indentation was larger into the camera, and its flashing was recorded on than the diameter of the BB (0.45 cm.). The the film to permit the establishment of a time density of steel is 7.8 and that of magnesium is scale of events. 1.7 (Fig. 1). With either projectile, the same amount of kinetic energy was delivered to the eye The high-speed negative films|| used were 100 (K.E. = % mv.- = 0.68 joule). The mold con- feet long. Their relatively low sensitivity required taining the eye was rigidly mounted at a distance powerful illumination by 3, 625 watt projectors. of 2 to 3 cm. from the muzzle of the gun. This "General Electric 1531-p2. was necessary to insure alignment of the center of {General Electric 1531-A. JPolaroid Type 57 (3000 ASA black and white). "The eyes were supplied by the Boston Eye Bank. $Hycam. K1001, Red Lake Laboratories. fDaisy Manufacturing Company, Rodgers, Ark. ||Eastman Kodak Tri-X (ASA 400) and 4-X (ASA 443). Downloaded from iovs.arvojournals.org on 09/28/2021 292 Delori, Pomerantzeff, and Cox Investigative Ophthalmology June 1969 SCOTCH LITE SCREEN SOLENOIDS MANUAL CONTROLS CONTROL FOR PRESETTING TIME DELAY Fig. 2. Schematic illustration of the setup for single flash high-speed photography. SCREEN ILLUMINATION DIFFUSING SCREEN DIRECT l» ILLUMINATION CONTROL NEON TIME MARKER P.S. CONTROL -FOR FILM SPEED a FUSE Fig. 3. Schematic illustration of the setup for high-speed cinematography. Downloaded from iovs.arvojournals.org on 09/28/2021 Vulume 8 Globe deformation under high-speed impact 293 Number 3 This method was more informative than the single flash procedure since the complete event was re- corded in one film strip. The picture quality, how- ever, was inferior because of the lower sensitivity of the film and the longer exposure time (50 to 70 fisec instead of 3 /isec). Ten high-speed movies were taken of pig eyes and 2 of human eyes. Other methods.