A trip to the optometrist for eye care involves plenty of digital imaging
I recently visited my optometrist for a regular checkup, briefly leaving behind topics of machine vision to focus on my own human vision…or so I thought. Turns out there was almost as much digital imaging waiting for me at my doctor’s office as at my own.
Besides the usual acuity charts and prescription checks (and my arch-nemesis, the intra-ocular pressure “puff” machine), Dr. Howard Dolman of Dolman Eyecare was firm in his desire to dilate my pupils to carefully examine and take images of the inside of my eyes. I’ll admit I hate that part, since after the dilation drops everything seems so bright I need to wear sunglasses indoors for the next four hours. But as the good doctor explained the “why” and the “how” of these images, I became more and more interested.
Worldwide, glaucoma is the second leading cause of blindness after cataracts (says Wikipedia), affecting 1 in 200 people under age 50, 1 in 10 over age 80, and a much higher proportion of diabetics of all ages. It can be caused by high pressure inside the eye and is characterized by damage to the retina and optic nerve, generally starting from the periphery (and resulting in “tunnel vision”). It can come on quickly and painfully, which patients notice immediately, but it can also progress much more slowly; those affected may not notice problems until the disorder has already caused significant damage…and while there are treatments to slow or even halt the advance of the condition, the damage is incurable and irreversible. Early detection is therefore critical.
With this and other threats in mind, optometrists nowadays image the inside of the eye in several ways. They take color and monochrome images of the retina and its vascularization (veins), looking for signs of current problems or hints of future issues. And as Dr. Dolman explained to me, they now have the technology to take not just 2D photos, but high resolution 3D imagery through a technique called optical coherence tomography (OCT). OCT uses multiple (safe) wavelengths of lasers to create interference patterns in the near infrared spectrum several millimeters deep into the back of the retina that can be detected (by appropriately tuned CCD and CMOS image sensors and image processors) and interpreted into 3D data for unprecedented “insight.”
Dr. Dolman showed images of my own eye (above) on his screens. The image data can also be modeled in 3D animations, such as this striking example from Zentrum für Medizinische Physik und Biomedizinische Technik.
The advantages of this approach are compelling. High resolution, real-time, non-invasive imaging that can see under the surface to reveal features or problems long before they are detectable any other way. OCT can flag issues with glaucoma, macular degeneration, and a range of other serious conditions literally years before they become noticeable by any other means, giving doctors and patients precious time to take action. And even if there are no issues to address, OCT images provide an important baseline for future reference.
Needless to say, I was sold. A few hours of mild sunglass-related ridicule from my kids (“Future’s so bright, eh dad?”) was worth it. It was also good to be reminded just how many other applications beyond machine vision depend on digital imaging…come to think of it I have an appointment with the dentist coming up and I believe I’m due for x-rays. Stay tuned.