In the 30 years since optical coherence tomography was first described, it has become one of the most widely used technologies for imaging the human eye.
Optical coherence tomography (OCT) is today regarded as a standard diagnostic technique in various ophthalmology sub-disciplines. It is essential for diagnosing blinding diseases such as macular degeneration, glaucoma and diabetic retinopathy at early, treatable stages before irreversible loss of vision occurs.1–3
In a similar way to ultrasound, OCT measures the ‘time of flight’ distribution of light that is reflected from tissue and is based on low-coherence interferometry, typically using near-infrared light because the relatively long wavelength allows it to penetrate the scattering medium. It was in the 1980s that imaging of biological tissue, especially of the human eye, started to be investigated in parallel by several groups worldwide.
The first two-dimensional picture of the fundus of a human eye in vivo was created by the late Adolf Friedrich Fercher in 1990, using white light interferometry. He presented his results at the International Commission for Optics congress that year.4,5 Fercher’s visionary ideas laid the basis for the development of OCT and the first in vitro OCT images were published by German and United States researchers in 1991.6,8–10
After graduating with a degree in physics in 1968, Fercher worked at Carl Zeiss, Germany, on optical testing, computer holography and holographic interferometry. In 1975, he became a professor at the University of Essen, Germany; from 1986 he was professor of medical physics, later chair of the Department of Medical Physics, at the Medical School of the University of Vienna. He retired in 2008.1
Fercher published his first paper on the biomedical applications of optics while he was still working for Carl Zeiss,7 applying Mie theory to calculate light scattering in a simplified model cell. He showed that the scattered signal oscillates as a function of scattering angle and that the oscillation length is related to particle diameter. Although he did not continue this work, it demonstrates his early interest in biomedical optics.1,7
It was during his time at the University of Vienna that Fercher and his colleagues worked on low-, partial coherence and white light interferometry for in vivo imaging of biological tissue. Their focus was on the human eye.
Although the image quality of Fercher’s 2-D interferometric depth scans of the fundus was poor compared with modern standards, the retinal thickness, the excavation of the optic disc and the lamina cribrosa were visible.8
Next, Dr David Huang and colleagues from a group led by Dr James Fujimoto at Massachusetts Institute of Technology, the US, were the first to synthesise optical A-scans to 2-D images (B-scans), demonstrating the potential of this technology to record cross-sectional images of translucent and scattering tissue.1 Dr Huang named this new diagnostic technique ‘optical coherence tomography.’11 The first commercially available OCT device went on to be launched by Humphrey Instruments in 1996.12
It is clear that Fercher’s pioneering ideas were far ahead of his time. When he first published his scientific results, it was perhaps obvious only to him how fundamentally his research would change ophthalmology. This technology has contributed to an advanced understanding of disease mechanisms and treatments, including ‘in vivo histology’ and intraoperative monitoring in multiple disciplines including ophthalmology, cardiology and cancer.