Here is our latest lecture on eye trauma, where I discuss many causes of ocular trauma: heat injury, projectiles (airsoft, paintball, bb gun), chemical burns, laser, and explosive trauma. You can watch this lecture in high-resolution 720p by changing the settings to “HD” in the player below (or by watching the
YouTube version in HD mode) or by downloading the 720p file below. This is a graphic presentation … so you might want to watch in full-screen mode for the full effect. Enjoy! Download
ExplodingEye.m4v (229 mb)
ExplodingEye720p.m4v (1000 mb) Screen Shots From this Video (comments below)
The eye is relatively protected from heat and fire damage by its location within the skull.
It also helps that the eye is filled with water (vitreous). Water makes a great conductor of heat, and can dissipate energy. For example, if you hold a balloon over a candle, it will pop immediately. However, if you put water in a balloon and repeat this candle experiment … it will NOT explode. In fact, you can even boil water inside a balloon if you are patient enough.
It’s been about 10 years since I visited Disney World. At the time, it was early in my eye career and I was terrified that tourists (all holding cigarettes at child’s eye height) were going to injure a child by poking their eye with a lit end. Fortunately, cigarettes have a small flame, and the tear surface can immediately quench most of it if the cigarette is only a glancing blow. You prove this by putting out a cigarette on your hand (or even your tongue).
Applying a lit cigarette to a pig eye, we find surprisingly little burn damage on the surface.
Electronic cigarettes don’t cause any burn damage to the eye at all!
One injury we see on occasion is a sparkler in the eye. This typically occurs in small children who are given a sparkler to hold on holidays.
Sparklers are dangerous, primarily because the metals they contain (such as magnesium) burn at extremely high temperature. This is a magnesium strip … not only does it burn brightly, but it doesn’t quench well in water.
The eye’s tear film doesn’t have a chance to quench a magnesium fire, so significant ocular burns can occur.
BB guns, airsoft, and paintball are the main penetrating ocular injuries we see with children. In an attempt to estimate the relative damage these “toys” create, we can use a ballistic pendulum. This is a simple plastic block suspended by strings. When shot from the side, the block moves and a scale measures how far it traverses.
We can also calculate the kinetic energy knowing the weight and velocity of the pellets (bbs, paintballs, airsoft pellet). The equation is KINETIC ENERGY = 1/2 x MASS x VELOCITY SQUARED. A BB gun gives about 2 joules.
Airsoft has half the kinetic energy of a steel bb.
Paintball, on the other hand, has 15 joules of kinetic energy. That’s about ten times the amount of BB and Airsoft pellet!
When estimating the damage created by a projectile (bb gun, paintball, airsoft pellet) … the penetrating power of these items must be considered. After all, a single nail can easily pop a balloon with little force. Make that 100 nails, however, and you have a different proposition.
I then test each of the guns on tin cans and tomatoes to test their penetrating power. Despite its low kinetic energy, the steel bb gun penetrates the best.
To to test the penetrating power of these guns, I placed a pig eye in this skull model, and shoot it with each weapon.
The BB gun penetrates through the cornea with no problem at all, with extremely gory results.
Airsoft pellets do NOT penetrate through the cornea … even when shot on full automatic.
The paintball completely destroys the eye. Like hitting the eye with a hammer, the globe explodes.
To demonstrate the damage that acids create on tissue, I perform a simple experiment involving sulfuric acid and sugar.
Sulfuric acid reacts with sugar to create an exothermic reaction.
As the water boils off, all that is left is a carbon residue.
This carbon crust is similar to the crust or “eschar” that forms with acid burns to the eye. Coagulation necrosis and other debris can limit deeper penetration into tissue.
This is in contrast to bases. Base burns denature proteins, breakdown cell walls, and goes deeper and deeper in the skin and eye.
This experiment tests whether acids or bases will cause more tissue damage to the eye. I’ve filled the right glass with 95% sulfuric acid and the left sodium hydroxide (lye).
After dipping these pig eyes in the chemicals, the base causes much more damage … liquefying the tissue and destroying the globe.
After a few more minutes of base burn, the scleral wall has mostly broken down. You can see the dark uveal tissue (retina, choroid) and the internal lens in the middle.
It’s quite obvious here that the base has caused more damage than the acid … the eye on the right has only suffered from surface layer acidic cooking.
This is the Crookes Radiometer. When first invented, it was thought to demonstrate the particle nature of light. Light photons were absorbed by the black panels, and bounced off the white, creating motion. The true mechanism of how this works is more complex, involving the generation of heat along the black panels and air-currents within a partial vacuum. Either way … this radiometer is essentially a “solar mill” and demonstrates that light can transmit energy.
This is a high-powered laser from Dragon Lasers. It has a power of 1000mW (1 Watt). Most laser pointers, in contrast, have a power of only 3-5mW. This laser is therefor about 200 times more powerful.
This is evident when shooting at balloons. Here you can see the laser shooting through a line of balloons in only a split-second.
I can’t demonstrate retinal laser burns in this pig eye (unfortunately, the corneas are too cloudy to transmit light) but we can see that this laser will burn the eye.
Laser cornea burn
This is a modern m80 firecracker. M-80s were originally created by the military to simulate gun and artillery fire. They caused a lot of injuries and were banned during the 60s. The “modern version” seen in this picture isn’t as powerful … it’s just a regular “firecracker” with a larger housing to make it seem powerful. You know it’s a fake because the fuse/wick also comes out the end (the original m80 had a fuse that came out the side).
During this part of the video, I show the damage of fireworks in an open and closed clay hand.
We then explore the affect of firecrackers near the eye (this is a pig eye from a student dissection kit).
Despite the firecracker explosion, the eye hasn’t ruptured.
Enclosing the eye with a hand, creates a more intense explosion.
Bottle Rockets can injure the eye from impact and explosive forces.
With blunt and concusive trauma, the eye tends to rupture at two places. The most obvious site is at the limbus (at the edge of the cornea). A rupture here is quite obvious, as the uveal tissue (iris) will extrude outward. Repair can be challenging but surgical access is straightforward.
The other location for a rupture is at the insertion of the rectus muscles on the eye. The scleral wall is very thin at these insertion points. These ruptures are much more difficult to get access to, and may even require temporary disinsertion of the muscles during the repair.
In a case of suspected rupture globe, where the limbus is intact … we may have to explore under the muscles to find the scleral rupture.