If you’re like me, welcoming a new year always comes with time to reflect on the past one. And there’s no doubt that 2022 was eventful. We experienced one of the hottest summers on record, back-to-back hurricanes, and now winter storms that caused snow in Miami for the first time since 1977.
Of course, these things should not stop you from enjoying your favorite activities, right? So, while I was up North this winter taking a walk outside, I had a question -- what would happen if your eye froze? How would your vision change? Instantly, thinking about this felt quite uncomfortable. And the answer is just as uncomfortable, even a little bit morbid.
Before I unlock a new fear, I will say that it is highly unlikely that your eyes would freeze completely -- while you are still alive anyway. Your eyes have natural defense mechanisms such as salts and proteins to avoid this. The only real case I could find that’s close to this scenario is corneal frostbite, but that is also quite rare. This is only a thought experiment and should not be taken seriously.
Now, your eye is made up of liquid and tissues that function as lenses. With this in mind, I knew that Ansys Zemax OpticStudio would be the right tool for the job. Instead of reinventing the very known and heavily modeled human eye, I found a model file from the Zemax knowledgebase to use as my starting point. To keep the simulation simple and straightforward, I used a sequential mode here. That means we are going to ignore the total internal reflection for this use case.
Figure 1. Layout of human eye in Zemax.
Figure 2. Extended Diffraction Image Analysis of Letter F for the unfrozen eye.
Let’s start with a human eye that has 20/20 vision with an “infinite focus”. The layout in figure 1 pinpoints each part of the eye. In figure 2, we simulate what this eye would see when looking at the letter F. To make things simple, we are going to keep it in grayscale like the Snellen Eye Chart, which you would use at a doctor’s office.
Figure 3. Extended Diffraction Image Analysis of Letter F for the frozen eye
Now, what if your eye froze! To simulate this, I changed all the materials of the eye to represent ice with a refractive index of 1.31. The results were extremely jarring. As seen in figure 3, the F now is showing distortion with a circular or spiral blurriness. To put it lightly, the vision was greatly impaired.
Figure 4. Layout of ice glasses with human eye.
This led me down another train of thought. Staying within the land of the theoretical, if this happened to you outside in the winter, how could you fix it? Making glasses out of ice of course! In the simulation, I was looking to recreate the vision of the unfrozen eye. To do this, I added a lens in front of the eye with a thickness of 3 mm and a material of -- you guessed it -- ice! Then, I optimized for the best spot size (focus) through the merit function wizard. We can see the layout of the ice glasses in front of the eye in figure 4.
Figure 5. Extended Diffraction Image Analysis of Letter F for the frozen eye with ice glasses.
Figure 6. Ice glasses lens shaded model.
We see the result of the ice glasses in figure 5; they would bring the vision back to normal. And in figure 6, we see what the ice glasses lens would look like! They have a radius of curvature of about 9.88 mm in the front and 8.64 mm in the back. The glasses lens resembles a hollow demi-sphere, or if you were a kid in the 90s, those hollowed-out rubber popper toys that we’d turn inside out and watch POP.
So there you go! That is what you would see if your eye was frozen, and how you could make glasses out of ice to see once again. In addition to sending a shiver down your spine as you imagine your eyeballs freezing, this shows how easy it is to create lenses to adjust vision and optimize for best focus using Ansys Zemax.
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