Original article
Ophthalmic imaging by spectral optical coherence tomography

https://doi.org/10.1016/j.ajo.2004.04.049Get rights and content

Abstract

Purpose

To demonstrate two novel ophthalmic imaging techniques based on fast Spectral Optical Coherence Tomography (SOCT).

Design

Prospective observation case report.

Methods

Setting

Research laboratory.

Study population

A normal human subject.

Main outcome measures

Correlation of an optical coherence retinal tomogram with known retinal anatomy, reduction of eye exposure to the probing light beam during Optical Coherence Tomography (OCT) examination.

Results

High resolution (3- × 20-μm) cross-sectional 2-dimensional images of the human retina in vivo have been obtained with only 0.1-second total illumination time (for 1024 A-scans), and approximately 200- μW eye exposure. Details of the optic disk in vivo have been visualized at a rate of eight frames per second, which is sufficient to provide real time analysis. The 3-dimensional images of the optic nerve correspond to the images obtained from a fundus camera.

Conclusions

Because of its short acquisition time and high sensitivity, SOCT uses a 100 times lower exposure/A-scan to obtain images of comparable quality to those obtained by the commercial instrument based on traditional time-domain OCT. Spectral Optical Conherence Tomography therefore provides a much wider safety margin than the traditional method and allows relaxation of the current safety precautions forbidding more than 10 minutes/day scanning of the same location of a retina. As a result of the high speed offered by the new technique, the 3-dmensional tomograms, which allow a surgeon access to a comprehensive and detailed view of relevant pathologies, are obtained in a much shorter, clinically more reasonable time.

Section snippets

Methods

The SOCT instrument is based on an open-air Michelson interferometer set-up. Two types of light sources are used in the experiments presented here. For high-resolution images, a pulse train from a home-built femtosecond Ti:Sapphire laser (4-nJ pulse energy, 80-MHz repetition rate, 40-nm full-width-half-maximum (FWHM) spectrum centered at a wavelength of 830 nm) is employed. The pulses are first compressed in a standard, double SF10 prism compressor, attenuated to approximately 2 nJ with a

Fast, high-resolution soct

Fast in vivo ophthalmic SOCT imaging with a broadband light beam generated in a photonic fiber is demonstrated in a normal human subject. Each A-scan is recorded during 128 μs and processed to yield a single line in a cross-sectional image. High resolution renders the images of a layered structure sharp and also provides the opportunity to locate and observe details at micrometer resolution.

A high resolution and high-speed SOCT horizontal cross-sectional image of the macular region of the human

Discussion

It is a well-established fact that an ultra-high resolution time domain OCT system provides unique information about ocular structures which, in the past, was only accessible by means of histology. As a result of its short acquisition time and high sensitivity,12 SOCT only needs to use a much lower exposure/A-scan to realize images of quality comparable to those obtained by traditional time domain OCT. It has also been employed to obtain functional information on retinal blood flow.13, 14 The

Supplementary files

Acknowledgements

This work was supported by Grant KBN 4T11E023 22, and an FNP′2003 Scholarship for Young Researchers.

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