Infrared Imaging/Meibography (Unpublished Draft)
This write-up is a quick technical explanation of how infrared imaging works. It is for those interested in the process used for infrared imaging, which includes patients, student doctors, or any other doctors interested in dry eye disease. I will also explain components used in my device.
Based on an article from 2013 here. I began experimenting with various imaging devices to create a new device to use within a clinical setting. The device was designed to be used as a portable handheld camera capable of infrared imaging.
What is infrared imaging?
Infrared imaging, when used to image glands, is nearly visible IR spectrum light, similar to the infrared light used by security cameras with night vision.
These cameras have an IR sensor built in. These are camera sensors that are sensitive to infrared light (generally 600-900nm). They are then combined with an filter that cuts visible light from the image. An external LED light source can provide illumination to the sensor through this filter. The camera can then be focused at near to produce IR images of any tissue.
How does this help with dry eye?
Infrared light can be used as a non-invasive way to visualize structures beneath the surface of the skin.
IR light is commonly used as is within an optometric in several instruments as is. These include fundus cameras, perimeters, and autorefractors. The human pupil does not respond to infrared light and therefore can be used to properly align a fundus camera prior to firing visible light into the retina in a non-mydriatic fundus camera.
When an IR camera is directed under the lid, various vasculature will absorb IR light, and more importantly, glands will reflect IR light and appear as brighter areas.
How does the device work?
With the advent of hobbyist CAD software, 3D printing, open Android based apps, the school of YouTube, and various articles found online, I was able to put together a rough draft for a camera that could plug into any Android based phone and be used as an IR imaging device.
After a little research, a USB based security camera module contains all of the items necessary to create an imaging device. Most security cameras will employ the use of IR LEDs in a ring to illuminate an environment. These LEDs emit near IR light that can be used to illuminate tissue. The module also contains an objective lens that can be altered to be focused at a convenient distance (typically ~10cm away from the camera). Using CAD software, a casing was created to house all of the hardware, an IR-pass filter, and all necessary wiring to complete the project.
What does this mean for the patient?
IR imaging when directed at meibomian glands is called meibography. Commercially available devices can come at a significant cost, and only offer diagnostic information. IR imaging offers no real treatment value. Therefore, having access to this technology may reveal structural problems with meibomian glands, but will offer little to no use without further investment in a treatment tools.
At this point in time it may not make financial sense to invest in such a device. Using an inexpensive device to capture high definition images that provide the diagnostic data can help optometrist provide dry eye diagnostic services at a reduced cost - I perform IR imaging routinely at no cost for anyone who presents with any ocular surface disease or with potential signs of meibomian gland dysfunction. Ultimately this allows a clearer discussion with the patient in potential treatments.
What does it look like?
Using Fusion360 (CAD software), precise measurements could be made to house the components necessary for the camera.
Next, a USB based camera module was purchased from a supplier off of AliExpress. There are several kinds that have various capabilities, compatibility, and costs. The key to any of these modules is that they must be USB based and compatible with the USB Video Class (UVC). This basically means that when it's plugged into any device compatible with UVC devices, it will work just like a webcam (meaning this device is Windows, Mac, and Android compatible).
What do the images look like?
The images produced by this camera is heavily dependent on the UVC camera used to create it. There was a little trial and error with that, but eventually, useable images were created. Blood vessels could be visualized, and gland structure could easily be seen right on the phone. After this, a treatment plan can be discussed with the patient. In office treatments I provide are forced gland express, microblepharoexfoliation using sterile cotton swabs, tea-tree oil treatments, and various other medical therapies (drops or other medications). My goal with all of this is to provide a budget friendly option to my patients when it comes to dry eye disease and treatment. If all else fails, more expensive treatments can be arranged at other offices.
How can you make your own?
I do share instructions on how to build this device on your own, but do not have anything formally prepared in a step-by-step format at this time, but maybe in the future. Any directions can be directed to my office via email at DrPatel@BridgelandOptometry.ca.