The Imaging Revolution

The Imaging Revolution

Powerful imaging technology may be transforming the clinical practice of eye medicine, especially in the practices of retina and glaucoma specialists.
Virtually every anatomic structure of the eye is becoming more visually accessible thanks to imaging technologies that didn’t exist 10 years ago. New advances in optical coherence tomography (OCT) and autofluorescence (AF) imaging, in particular, are gathering attention both in the United States and internationally.

Specialists agree that these technologies are dynamic works in progress and represent different stages of development. The two share a common strength: Both are noninvasive. As is common, however, with emerging technologies, there are issues yet to be resolved.

A New Generation of OCT

The major applications of conventional OCT have been in retinal disease and glaucoma. “OCT and other emerging technologies have been changing the way we practice medicine,” said Joel S. Schuman, MD, professor and chairman of ophthalmology at the University of Pittsburgh. “OCT gives an objective assessment of the ocular structure and standardizes that information at a very high, expert level,” he said.
The third dimension. Conventional OCT has been giving way to versions with three-dimensional, high-speed, high-resolution capabilities, also known as 3-D, spectral or Fourier-domain OCT.
Three-dimensional OCT is from 50 to 100 times faster than previous-generation OCT.

Autofluorescence, the Metabolic Modality

The contemporary use of autofluorescence is comparable to the earlier days of OCT, according to Howard F. Fine, MD, MHSc, medical director of the Gerstner Clinical Research Center in Vision at Columbia University. “Just as OCT started out as a research tool and has become an indispensable clinical tool in most retina practices, autofluorescence is emerging from its research role into clinical applications,” Dr. Fine said.

The primary applications of AF imaging are in assessing the health of the retinal pigment epithelium in diseases such as geographic atrophy from AMD, pathologic myopia and central serous chorioretinopathy. Less common disorders that are well-imaged with AF include dystrophies and degenerations, especially those that affect the metabolism of lipofuscin, such as Stargardt’s disease, according to Dr. Fine.

Monitoring metabolism. AF imaging, unlike OCT, is a form of metabolic mapping. It visualizes not only morphology but also metabolic changes. “The two imaging modalities serve different purposes,” said Frank G. Holz, MD, professor and chairman of ophthalmology at the University of Bonn in Germany. “One imaging technique does not replace the other imaging technique.” Dr. Holz pointed out that autofluorescence imaging gives information over and above conventional imaging techniques like fundus photography or fluorescein angiography.