Dry Eye PID Hot Compress
As a long time sufferer of dry eyes, I have tried countless drops and treatments to try to find relief of irritated eyes. It turns out that what most people refer to as dry eye is actually not that the eye is producing insufficient tears, but rather the oil layer, which covers the tears and keeps them from evaporating is not functioning properly. Due to inflammation, over time oil glands located in the eyelids, produce oil (meibum) that is more of a toothpaste like consistency rather than a healthy olive oil type. This sludge like oil causes mechanical irritation to the eye during each blink as well as allowing the tears to evaporate off the surface of the eye.
One current form of treatment is to apply heat to melt the meibum to unclog the glands and reduce irritation. The most popular method is using a microwaveable hot compress and applied to the eyes. The problem with this is that it common to initially burn the skin as there is no way to control the temperature. The other issue is that the heat only lasts for a few minutes and studies have shown it is not long enough for the heat to penetrate the eyelid and empty gland contents.
I wanted to create a hot compress that supplied the correct amount of heat (around 45C) and could do it consistently for about 10 minutes (time that many medical studies have shown for for heat to penetrate eyelids and unclog oil glands). To perform this, I built a closed loop PID heat mask using an Arduino Nano and flexible resistive heaters inserted into a cloth mask. I designed and created my own custom pcb to make the device robust enough to use on a daily basis. The temperature for each eye is displayed via LCD screen and read via thermistors placed between the mask and the eye to guarantee correct meibum melting temperatures. The set temperature is adjustable by potentiometer and the device is powered by 12VDC. I also added thermistors tied directly to the heater itself to ensure the device is shutoff in case excessive temperatures are reached.