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D. Cabrera DeBuc et al.
daily routine have resulted in some of the mean changes to the understanding and
management of retinal diseases [2].
OCT uses retroreflected light to provide micron-resolution, cross-sectional scans
of biological tissues [3–5]. The first micron-resolution OCT system for imaging the
human retina in vivo was introduced in 1991 [3]. OCT is a compelling medical
imaging technology in ophthalmology because it enables visualization of the crosssectional structure of the retina and anterior eye with higher resolutions than any
other non-invasive imaging modality [3]. The depth resolution of OCT is excellent,
typically on the order of 0.01 mm or 0.4 thousandths of an inch. An OCT image
represents a cross-sectional, micron-scale picture of the optical reflectance properties
of the tissue [3]. This image can either be used to assess tissue features and pathologies
qualitatively or to make quantitative measurements objectively.
2.2 Developments and Principles of Operation of Optical
Coherence Tomography
OCT is an extension of optical coherence domain reflectometry to imaging in two
or three dimensions [6]. This imaging technique generates a cross-sectional image
by recording axial reflectance profiles while the transverse position of the optical
beam on the sample is scanned. Thus, the longitudinal location of tissue structures is
determined by measuring the time-of-flight delays of light backscattered from these
structures. The optical delays are measured by low coherence interferometry. The
light reflected from deeper layers has a longer propagation delay than light reflected
from more superficial layers.
OCT can be used for retinal and anterior segment imaging. The OCT for ophthalmic examination is similar to a combination of a slit lamp for anterior segment
imaging and a fundus camera for retinal imaging. The instrumentation includes a
video display for operator viewing of the anterior segment or fundus while obtaining
the OCT images and a simultaneous computer display of the tomograms. Images are
stored via computer for the diagnostic record [7].
2.2.1 Time Domain OCT
Conventional or time domain OCT (TD-OCT) is based on the principle of low coherence interferometry: a powerful tool to “section” a transparent object. Low coherence
means that the system employs a wide range of wavelengths. The most straightforward and currently the most common interferometer for OCT is a simple Michelson
interferometer [8]. The scheme of a typical fiber optics TD-OCT system is shown in
Fig. 2.1. A low-coherence source illuminates the interferometer. The light is split by
a 50/50 fiber-coupler into a sample and a reference path. Light retroreflected from
D. Cabrera DeBuc et al.
daily routine have resulted in some of the mean changes to the understanding and
management of retinal diseases [2].
OCT uses retroreflected light to provide micron-resolution, cross-sectional scans
of biological tissues [3–5]. The first micron-resolution OCT system for imaging the
human retina in vivo was introduced in 1991 [3]. OCT is a compelling medical
imaging technology in ophthalmology because it enables visualization of the crosssectional structure of the retina and anterior eye with higher resolutions than any
other non-invasive imaging modality [3]. The depth resolution of OCT is excellent,
typically on the order of 0.01 mm or 0.4 thousandths of an inch. An OCT image
represents a cross-sectional, micron-scale picture of the optical reflectance properties
of the tissue [3]. This image can either be used to assess tissue features and pathologies
qualitatively or to make quantitative measurements objectively.
2.2 Developments and Principles of Operation of Optical
Coherence Tomography
OCT is an extension of optical coherence domain reflectometry to imaging in two
or three dimensions [6]. This imaging technique generates a cross-sectional image
by recording axial reflectance profiles while the transverse position of the optical
beam on the sample is scanned. Thus, the longitudinal location of tissue structures is
determined by measuring the time-of-flight delays of light backscattered from these
structures. The optical delays are measured by low coherence interferometry. The
light reflected from deeper layers has a longer propagation delay than light reflected
from more superficial layers.
OCT can be used for retinal and anterior segment imaging. The OCT for ophthalmic examination is similar to a combination of a slit lamp for anterior segment
imaging and a fundus camera for retinal imaging. The instrumentation includes a
video display for operator viewing of the anterior segment or fundus while obtaining
the OCT images and a simultaneous computer display of the tomograms. Images are
stored via computer for the diagnostic record [7].
2.2.1 Time Domain OCT
Conventional or time domain OCT (TD-OCT) is based on the principle of low coherence interferometry: a powerful tool to “section” a transparent object. Low coherence
means that the system employs a wide range of wavelengths. The most straightforward and currently the most common interferometer for OCT is a simple Michelson
interferometer [8]. The scheme of a typical fiber optics TD-OCT system is shown in
Fig. 2.1. A low-coherence source illuminates the interferometer. The light is split by
a 50/50 fiber-coupler into a sample and a reference path. Light retroreflected from