Talisa E. de Carlo, MD
Vitreoretinal Surgery Fellow
University of Colorado
The highlight of yet another terrific Pacific Retina Club meeting was the Alexander R. Irvine Lecture: “OCT – Past, Present and Future” presented by Dr. Jay Duker (Tufts University). Dr. Richard McDonald (West Coast Retina) introduced the invited speaker – stating that Dr. Duker “makes us all want to be a better doctor.” Having previously had the pleasure of working with Dr. Duker as one of his many research fellows, I couldn’t agree more and can think of few others as qualified to present a thoughtful review of the history of OCT. Dr. Duker is a dedicated mentor, incredible diagnostician, and an inspiring innovator.
Dr. Duker began our journey through the past, present, and future of OCT by recognizing the giants of OCT – Drs. Fujimoto, Puliafito, Huang, Schuman, and Waheed – without whom this incredible technology would not have developed into the multifaceted tool we use every day. OCT was first developed by Dr. James Fujimoto (Massachusetts Institute of Technology) for use in corneal imaging but was quickly adapted for use as an “in situ optical biopsy” of the retina. Since then, the technology has been developed for wide applicability in non-ophthalmologic fields such as GI, neurology, cardiology, dentistry, and dermatology.
In 1991 Dr. Huang published the first OCT of the retina, a pixelated first step for a technology that would evolve rapidly over the next 30 years. The first prototype OCT, which employed time-domain technology, was used to image patients at Tufts University in 1993. In 1996 the technology transferred to Zeiss who produced the OCT 1. However, it wasn’t until 2002 that the first commercially available OCT 3 came on market. This OCT 3 sported a normative database, produced images with a 10 um axial resolution, and captured images at 400 A-scan/second – a far cry from the ultrahigh speed 400,000 A-scan/second modern prototypes out of Dr. Fujimoto’s lab.
Image quality improved drastically with the development of Fourier domain technologies – spectral domain and swept source OCT. In 2004 the first SD-OCT was reported at 20,000 A-scans/sec. The axial resolution improved to 4-7um and the faster imaging speeds allowed for over-sampling, thereby reducing artifact and noise. In 2013, faster imaging speeds were employed to develop my personal favorite OCT advancement – OCT angiography. SS-OCT, which offers better optical penetration to the choroid, is still less adopted mainly due to cost and the superb utility of its predecessor SD-OCT.
Dr. Duker then reviewed all the incredible advancements and adaptations of the OCT technology we have today. Various anterior and posterior scan types, mechanical tracking, software updates, montage techniques, and ganglion cell and RNFL analyses have wide applicability for clinical use. We have faster cameras, multiple cameras in a single device, “low-end” OCT for screening capabilities, and even the development of fully automated OCT devices where no photographer is necessary to capture an image. Peripheral OCT can be used to easily differentiate retinal detachment from retinoschisis, macular thickness mapping can quickly show changes in retinal edema, summed voxel projection provide red-free-like images, and Dr. Spaide’s brain-child of enhanced-depth imaging allows for better visualization of the choroid. Further, en face OCT can be used for quantification of drusen, PED, and GA volumes. His enthusiasm for the technology was infectious!
Already on the edge of our seats, the audience was then treated to Dr. Duker’s visions for tomorrow and the OCT technologies in development. He described technologies with great promise such as intraoperative OCT, whole-globe OCT being developed by Dr. Fujimoto, and the use of machine learning and AI. He proposed that AI would offer better screening by PCPs and optometrists using low-end OCT, enhance image quality, and even provide pattern recognition and diagnosis. Dr. Duker also described developing technologies with limited current clinical applicability due to lack of treatment options but possible future utility such as adaptive optics, which allows for greatly improved resolution of a small scanning area, and functional OCT, which measures changes to the size and configuration of photoreceptors with the addition of light. He showed us beautiful images to demonstrate the novel VISTA protocol (variable interscan time analysis), which allows for visualization of slower flow vasculature such as the choroid and microaneurysms, and detection of relative differences in flow. Advancements in imaging speeds, new light source, and updates to the OCTA technology, he mused, would provide even more options for adaptations in the future.
After a roaring round of applause Dr. Spaide summarized the audience’s thoughts by praising Dr. Duker saying that “the heart of all of this was you.” Dr. Duker concluded that he had a blast doing all this and left us with a final piece of wisdom: “do what makes you happy.”