Image resolution, tissue penetration, and scan speed are among the most important parameters when designing an OCT system for ophthalmic use. Human retinal tissue is highly reflective in the near infrared spectrum range. A SLD at 820nm with 25nm FWHM spectral bandwidth provides 10μm coherence length in retinal tissue. Its appropriate power level, simplicity of use, high resolution, and relatively low cost, make the 820nm SLD the best choice light source for retinal OCT. A 1300nm SLD can penetrate deeper into the sclera tissue and since the 1300nm wavelength is highly absorbed in the vitreous, the ANSI laser safety standard allows higher maximum permissible power to the human eye. Higher scan speed can also be achieved. In this paper, we report two OCT systems that are designed specifically for retinal and anterior segment imaging of the human eye. Retinal OCT scans 400 A-scans per second, 2mm depth in tissue, and 10 μm image resolution with an 820nm SLD. Anterior segment OCT (AC-OCT) scans 2000 A-scans per second, 6mm depth in tissue, and 16μm image resolution with a 1300nm SLD. Benefits of suitable wavelength selection in scanning different tissue are clearly seen in the OCT images. Retinal OCT (OCT3) demonstrates significant improvement over the previous generation (OCT1/OCT2) from both a technical and cost point of view. AC-OCT performs 8 frames of 256 A-scans per second and is capable of imaging the human eye in vivo with minimum eye motion artifacts. It has potential use in refractive surgery, angle-closure glaucoma, and cataract surgery.
The early identification of glaucomatous development is extremely important for treatment of glaucoma. Analysis of optic-nerve-head features may play a crucial role for early glaucoma diagnostics. Here we propose a critical parameter, viz., nerve tissue area, which may prove to be extremely useful for detection of glaucoma in early stages. We report a novel and robust algorithm for OCT-based automatic, objective extraction of critical optic-nerve-head features such as optic disc, nerve tissue area, and optic cup for the first time.
We summarize the results of development of superluminescent diodes (SLEDs) for OCT applications. It is shown that powerful, wide spectrum and low rippled SLEDs may be realized at different spectral bands from 800 nm to 1600 nm on the base of relatively simple bent-angled SLED structure with double-layer protective/antireflective (AR) coatings on both facets of SLED crystal. Up to 100 mW free space and 30 mW SM fiber couple outputs are realized at 820 and 980 nm bands, and 15-35 mW free space (5-15 mW SM fiber) at 1550 nm and 1300 nm bands. Various methods to widen SLED spectrum are presented. 50 nm of gaussian-like spectrum is obtained from 1040 nm SLD. 70 nm FWHM and 20 mW free space output power is realized at 940 nm by u sing two-electrode pumping of strained QW SLED. 70 nm FWHM is obtained from 1550 nm band MQW SLED with 5 mW output power. All SLDs are characterized by very low parasitic Fabry-Perot modulation. Example of SLED use in commercial OCT setup is presented.
Conference Committee Involvement (2)
Coherence Domain Optical Methods and Optical Coherence Tomography in Biomedicine VIII
26 January 2004 | San Jose, CA, United States
Coherence Domain Optical Methods and Optical Coherence Tomography in Biomedicine VII
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.