Ultrahigh speed, ultrahigh resolution possible with spectral domain OCT

Spectral domain optical coherence tomography is a new technology that will enable intraocular imaging with “unprecedented simultaneous ultrahigh speed and ultrahigh resolution,” according to researchers at Harvard.

The spectral domain optical coherence tomography (OCT) system uses a superluminescent diode source to take in vivo images of the retina, the optic nerve head and retinal blood flow. To introduce this new technology, Teresa C. Chen, MD, and colleagues described their findings from imaging the right eye of a white male patient using the spectral domain OCT system.

The system takes images at a speed of 34.1 ms per A-scan, or about 73 times faster than currently available OCT instruments, according to Dr. Chen and coworkers. Single B scan images consisting of 1,000 A-scans can be acquired in 34.1 ms, which equates to a video imaging rate of 29 frames per second with an axial resolution of 6 µm.

Using a slower configuration, single images consisting of 500 A-scans can be acquired in 34 ms, allowing imaging of 29 frames per second with an axial resolution of 3.5 µm, which is three times better than commercially available OCT instruments, the study authors said.

The amount of energy directed into the eye is less than commercially available instruments and “is safe for intrabeam viewing for up to 8 hours at the same retinal location,” the authors said.

“Spectral domain technology not only offers structural retinal imaging but also allows imaging of retinal blood flow similar to Doppler ultrasound,” the authors said. “In eye diseases where OCT technology has already been shown to be useful, further improvements in spectral domain OCT technology may improve the diagnosis and treatment … decrease the need for other invasive ophthalmic tests and enhance understanding of eye disease pathophysiology.”

The study is published in the December issue of the Archives of Ophthalmology.